Works for almost all tests

19 files changed, 323 insertions, 1079 deletions

diff --git a/contracts/protocol/test/asset_proxy/proxies.ts b/contracts/protocol/test/asset_proxy/proxies.ts
index b2e7f5afb..650594c12 100644
--- a/contracts/protocol/test/asset_proxy/proxies.ts
+++ b/contracts/protocol/test/asset_proxy/proxies.ts
@@ -78,7 +78,6 @@ describe('Asset Transfer Proxies', () => {
         await blockchainLifecycle.revertAsync();
     });
     before(async () => {
-        console.log('1');
         const accounts = await web3Wrapper.getAvailableAddressesAsync();
         const usedAddresses = ([owner, notAuthorized, authorized, fromAddress, toAddress] = _.slice(accounts, 0, 5));
 
@@ -94,7 +93,6 @@ describe('Asset Transfer Proxies', () => {
             txDefaults,
         );
 
-        console.log('2');
         // Configure ERC20Proxy
         await web3Wrapper.awaitTransactionSuccessAsync(
             await erc20Proxy.addAuthorizedAddress.sendTransactionAsync(authorized, {
@@ -102,7 +100,6 @@ describe('Asset Transfer Proxies', () => {
             }),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
-        console.log('3');
         await web3Wrapper.awaitTransactionSuccessAsync(
             await erc20Proxy.addAuthorizedAddress.sendTransactionAsync(multiAssetProxy.address, {
                 from: owner,
@@ -110,7 +107,6 @@ describe('Asset Transfer Proxies', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
-        console.log('4');
 
         // Configure ERC721Proxy
         await web3Wrapper.awaitTransactionSuccessAsync(
@@ -120,7 +116,6 @@ describe('Asset Transfer Proxies', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
-        console.log('5');
         await web3Wrapper.awaitTransactionSuccessAsync(
             await erc721Proxy.addAuthorizedAddress.sendTransactionAsync(multiAssetProxy.address, {
                 from: owner,
@@ -128,7 +123,6 @@ describe('Asset Transfer Proxies', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
-        console.log('6');
 
         // Configure MultiAssetProxy
         await web3Wrapper.awaitTransactionSuccessAsync(
@@ -138,7 +132,6 @@ describe('Asset Transfer Proxies', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
-        console.log('7');
         await web3Wrapper.awaitTransactionSuccessAsync(
             await multiAssetProxy.registerAssetProxy.sendTransactionAsync(erc20Proxy.address, {
                 from: owner,
@@ -146,7 +139,6 @@ describe('Asset Transfer Proxies', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
-        console.log('8');
         await web3Wrapper.awaitTransactionSuccessAsync(
             await multiAssetProxy.registerAssetProxy.sendTransactionAsync(erc721Proxy.address, {
                 from: owner,
@@ -154,7 +146,6 @@ describe('Asset Transfer Proxies', () => {
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
 
-        console.log('9');
 
         // Deploy and configure ERC20 tokens
         const numDummyErc20ToDeploy = 2;
@@ -181,14 +172,12 @@ describe('Asset Transfer Proxies', () => {
             constants.DUMMY_TOKEN_TOTAL_SUPPLY,
         );
 
-        console.log('10');
 
         await erc20Wrapper.setBalancesAndAllowancesAsync();
         await web3Wrapper.awaitTransactionSuccessAsync(
             await noReturnErc20Token.setBalance.sendTransactionAsync(fromAddress, constants.INITIAL_ERC20_BALANCE),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
-        console.log('11');
         await web3Wrapper.awaitTransactionSuccessAsync(
             await noReturnErc20Token.approve.sendTransactionAsync(
                 erc20Proxy.address,
@@ -197,7 +186,6 @@ describe('Asset Transfer Proxies', () => {
             ),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
-        console.log('12');
         await web3Wrapper.awaitTransactionSuccessAsync(
             await multipleReturnErc20Token.setBalance.sendTransactionAsync(
                 fromAddress,
@@ -205,7 +193,6 @@ describe('Asset Transfer Proxies', () => {
             ),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
-        console.log('13');
         await web3Wrapper.awaitTransactionSuccessAsync(
             await multipleReturnErc20Token.approve.sendTransactionAsync(
                 erc20Proxy.address,
@@ -214,7 +201,6 @@ describe('Asset Transfer Proxies', () => {
             ),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
-        console.log('14');
 
         // Deploy and configure ERC721 tokens and receiver
         [erc721TokenA, erc721TokenB] = await erc721Wrapper.deployDummyTokensAsync();
@@ -223,12 +209,9 @@ describe('Asset Transfer Proxies', () => {
             provider,
             txDefaults,
         );
-        console.log('15');
 
         await erc721Wrapper.setBalancesAndAllowancesAsync();
-        console.log('16');
         const erc721Balances = await erc721Wrapper.getBalancesAsync();
-        console.log('17');
         erc721AFromTokenId = erc721Balances[fromAddress][erc721TokenA.address][0];
         erc721BFromTokenId = erc721Balances[fromAddress][erc721TokenB.address][0];
     });
diff --git a/contracts/protocol/test/exchange/internal.ts b/contracts/protocol/test/exchange/internal.ts
index 225890f02..ffe1f8a55 100644
--- a/contracts/protocol/test/exchange/internal.ts
+++ b/contracts/protocol/test/exchange/internal.ts
@@ -451,7 +451,6 @@ describe.skip('Exchange core internal functions', () => {
                 makerFeePaid: new BigNumber(0),
                 takerFeePaid: new BigNumber(0),
             };
-            //console.log(`EMPTY ORDER:\n ${JSON.stringify(emptySignedOrder, null ,4)}`);
             await web3Wrapper.awaitTransactionSuccessAsync(
                 await testExchange.publicUpdateFilledState.sendTransactionAsync(
                     orderUtils.getOrderWithoutExchangeAddress(emptySignedOrder),
diff --git a/contracts/protocol/test/utils/erc721_wrapper.ts b/contracts/protocol/test/utils/erc721_wrapper.ts
index 138fccf6f..1f658ce86 100644
--- a/contracts/protocol/test/utils/erc721_wrapper.ts
+++ b/contracts/protocol/test/utils/erc721_wrapper.ts
@@ -102,15 +102,12 @@ export class ERC721Wrapper {
     public async approveAsync(to: string, tokenAddress: string, tokenId: BigNumber): Promise<void> {
         const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
         const tokenOwner = await this.ownerOfAsync(tokenAddress, tokenId);
-        console.log('a');
-        console.log(to, ':', tokenId, ':', tokenOwner);
         await this._web3Wrapper.awaitTransactionSuccessAsync(
             await tokenContract.approve.sendTransactionAsync(to, tokenId, {
                 from: tokenOwner,
             }),
             constants.AWAIT_TRANSACTION_MINED_MS,
         );
-        console.log('b');
     }
     public async transferFromAsync(
         tokenAddress: string,
@@ -147,7 +144,6 @@ export class ERC721Wrapper {
     public async ownerOfAsync(tokenAddress: string, tokenId: BigNumber): Promise<string> {
         const tokenContract = this._getTokenContractFromAssetData(tokenAddress);
         const owner = await tokenContract.ownerOf.callAsync(tokenId);
-        console.log(`OWNER OF = ${owner}`);
         return owner;
     }
     public async isOwnerAsync(userAddress: string, tokenAddress: string, tokenId: BigNumber): Promise<boolean> {
diff --git a/packages/abi-gen-templates/partials/callAsync.handlebars b/packages/abi-gen-templates/partials/callAsync.handlebars
index 5b56be52e..d4fb772c7 100644
--- a/packages/abi-gen-templates/partials/callAsync.handlebars
+++ b/packages/abi-gen-templates/partials/callAsync.handlebars
@@ -5,8 +5,6 @@ async callAsync(
 ): Promise<{{> return_type outputs=outputs}}> {
     const self = this as any as {{contractName}}Contract;
     const functionSignature = '{{this.functionSignature}}';
-    const inputAbi = self._lookupAbi(functionSignature).inputs;
-    [{{> params inputs=inputs}}] = BaseContract._formatABIDataItemList(inputAbi, [{{> params inputs=inputs}}], BaseContract._bigNumberToString.bind(self));
     const abiEncoder = self._lookupAbiEncoder(functionSignature);
     const encodedData = abiEncoder.encode([{{> params inputs=inputs}}]);
     const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -19,10 +17,6 @@ async callAsync(
     );
     const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
     BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-    {{#if hasReturnValue}}
-    let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
+    let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
     return resultArray{{#singleReturnValue}}[0]{{/singleReturnValue}};
-    {{else}}
-    return;
-    {{/if}}
 },
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/asset_proxy_owner.ts b/packages/abi-gen-wrappers/src/generated-wrappers/asset_proxy_owner.ts
index 762de0dcb..4257004fd 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/asset_proxy_owner.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/asset_proxy_owner.ts
@@ -106,10 +106,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'owners(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -123,8 +119,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public removeOwner = {
@@ -187,10 +183,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'removeOwner(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [owner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [owner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([owner
         ]);
@@ -204,7 +196,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public revokeConfirmation = {
@@ -267,10 +260,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'revokeConfirmation(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [transactionId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [transactionId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([transactionId
         ]);
@@ -284,7 +273,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public isOwner = {
@@ -296,10 +286,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'isOwner(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -313,8 +299,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public confirmations = {
@@ -327,12 +313,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'confirmations(uint256,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0,
-        index_1
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0,
-        index_1
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0,
         index_1
@@ -347,8 +327,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public executeRemoveAuthorizedAddressAtIndex = {
@@ -411,10 +391,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'executeRemoveAuthorizedAddressAtIndex(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [transactionId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [transactionId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([transactionId
         ]);
@@ -428,7 +404,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public secondsTimeLocked = {
@@ -439,8 +416,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'secondsTimeLocked()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -453,8 +428,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getTransactionCount = {
@@ -467,12 +442,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'getTransactionCount(bool,bool)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [pending,
-        executed
-        ] = BaseContract._formatABIDataItemList(inputAbi, [pending,
-        executed
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([pending,
         executed
@@ -487,8 +456,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public registerAssetProxy = {
@@ -559,12 +528,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'registerAssetProxy(address,bool)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [assetProxyContract,
-        isRegistered
-        ] = BaseContract._formatABIDataItemList(inputAbi, [assetProxyContract,
-        isRegistered
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([assetProxyContract,
         isRegistered
@@ -579,7 +542,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public addOwner = {
@@ -642,10 +606,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'addOwner(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [owner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [owner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([owner
         ]);
@@ -659,7 +619,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public isConfirmed = {
@@ -671,10 +632,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'isConfirmed(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [transactionId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [transactionId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([transactionId
         ]);
@@ -688,8 +645,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public changeTimeLock = {
@@ -752,10 +709,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'changeTimeLock(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_secondsTimeLocked
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_secondsTimeLocked
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_secondsTimeLocked
         ]);
@@ -769,7 +722,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public isAssetProxyRegistered = {
@@ -781,10 +735,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'isAssetProxyRegistered(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -798,8 +748,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getConfirmationCount = {
@@ -811,10 +761,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'getConfirmationCount(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [transactionId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [transactionId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([transactionId
         ]);
@@ -828,8 +774,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transactions = {
@@ -841,10 +787,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'transactions(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -858,8 +800,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getOwners = {
@@ -870,8 +812,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'getOwners()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -884,8 +824,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getTransactionIds = {
@@ -900,16 +840,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'getTransactionIds(uint256,uint256,bool,bool)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [from,
-        to,
-        pending,
-        executed
-        ] = BaseContract._formatABIDataItemList(inputAbi, [from,
-        to,
-        pending,
-        executed
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([from,
         to,
@@ -926,8 +856,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getConfirmations = {
@@ -939,10 +869,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'getConfirmations(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [transactionId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [transactionId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([transactionId
         ]);
@@ -956,8 +882,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transactionCount = {
@@ -968,8 +894,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'transactionCount()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -982,8 +906,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public changeRequirement = {
@@ -1046,10 +970,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'changeRequirement(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_required
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_required
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_required
         ]);
@@ -1063,7 +983,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public confirmTransaction = {
@@ -1126,10 +1047,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'confirmTransaction(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [transactionId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [transactionId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([transactionId
         ]);
@@ -1143,7 +1060,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public submitTransaction = {
@@ -1222,14 +1140,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'submitTransaction(address,uint256,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [destination,
-        value,
-        data
-        ] = BaseContract._formatABIDataItemList(inputAbi, [destination,
-        value,
-        data
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([destination,
         value,
@@ -1245,8 +1155,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public confirmationTimes = {
@@ -1258,10 +1168,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'confirmationTimes(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -1275,8 +1181,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public MAX_OWNER_COUNT = {
@@ -1287,8 +1193,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'MAX_OWNER_COUNT()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -1301,8 +1205,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public required = {
@@ -1313,8 +1217,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'required()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -1327,8 +1229,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public replaceOwner = {
@@ -1399,12 +1301,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'replaceOwner(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [owner,
-        newOwner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [owner,
-        newOwner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([owner,
         newOwner
@@ -1419,7 +1315,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public executeTransaction = {
@@ -1482,10 +1379,6 @@ export class AssetProxyOwnerContract extends BaseContract {
         > {
             const self = this as any as AssetProxyOwnerContract;
             const functionSignature = 'executeTransaction(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [transactionId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [transactionId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([transactionId
         ]);
@@ -1499,7 +1392,8 @@ export class AssetProxyOwnerContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc20_token.ts b/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc20_token.ts
index b9d1a3371..6df58be56 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc20_token.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc20_token.ts
@@ -44,8 +44,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'name()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -58,8 +56,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public approve = {
@@ -130,12 +128,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'approve(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_spender,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_spender,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_spender,
         _value
@@ -150,8 +142,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public totalSupply = {
@@ -162,8 +154,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'totalSupply()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -176,8 +166,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferFrom = {
@@ -256,14 +246,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'transferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -279,8 +261,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public decimals = {
@@ -291,8 +273,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'decimals()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -305,8 +285,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public balanceOf = {
@@ -318,10 +298,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'balanceOf(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner
         ]);
@@ -335,8 +311,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public owner = {
@@ -347,8 +323,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'owner()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -361,8 +335,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public symbol = {
@@ -373,8 +347,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'symbol()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -387,8 +359,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public mint = {
@@ -451,10 +423,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'mint(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_value
         ]);
@@ -468,7 +436,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public transfer = {
@@ -539,12 +508,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'transfer(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_to,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_to,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_to,
         _value
@@ -559,8 +522,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public allowance = {
@@ -573,12 +536,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'allowance(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner,
-        _spender
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner,
-        _spender
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner,
         _spender
@@ -593,8 +550,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public setBalance = {
@@ -665,12 +622,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'setBalance(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_target,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_target,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_target,
         _value
@@ -685,7 +636,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public transferOwnership = {
@@ -748,10 +700,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'transferOwnership(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [newOwner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [newOwner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([newOwner
         ]);
@@ -765,7 +713,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public MAX_MINT_AMOUNT = {
@@ -776,8 +725,6 @@ export class DummyERC20TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC20TokenContract;
             const functionSignature = 'MAX_MINT_AMOUNT()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -790,8 +737,8 @@ export class DummyERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc721_token.ts b/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc721_token.ts
index ee1ffe60d..7ac08e61f 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc721_token.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/dummy_erc721_token.ts
@@ -52,8 +52,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'name()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -66,8 +64,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getApproved = {
@@ -79,10 +77,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'getApproved(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_tokenId
         ]);
@@ -96,8 +90,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public approve = {
@@ -168,12 +162,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'approve(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_approved,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_approved,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_approved,
         _tokenId
@@ -188,7 +176,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public transferFrom = {
@@ -267,14 +256,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'transferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -290,7 +271,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public mint = {
@@ -361,12 +343,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'mint(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_to,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_to,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_to,
         _tokenId
@@ -381,7 +357,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public safeTransferFrom1 = {
@@ -460,14 +437,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'safeTransferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -483,7 +452,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public ownerOf = {
@@ -495,10 +465,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'ownerOf(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_tokenId
         ]);
@@ -512,8 +478,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public balanceOf = {
@@ -525,10 +491,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'balanceOf(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner
         ]);
@@ -542,8 +504,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public owner = {
@@ -554,8 +516,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'owner()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -568,8 +528,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public symbol = {
@@ -580,8 +540,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'symbol()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -594,8 +552,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public burn = {
@@ -666,12 +624,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'burn(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner,
         _tokenId
@@ -686,7 +638,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public setApprovalForAll = {
@@ -757,12 +710,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'setApprovalForAll(address,bool)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_operator,
-        _approved
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_operator,
-        _approved
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_operator,
         _approved
@@ -777,7 +724,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public safeTransferFrom2 = {
@@ -864,16 +812,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'safeTransferFrom(address,address,uint256,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _tokenId,
-        _data
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _tokenId,
-        _data
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -890,7 +828,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public isApprovedForAll = {
@@ -903,12 +842,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'isApprovedForAll(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner,
-        _operator
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner,
-        _operator
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner,
         _operator
@@ -923,8 +856,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferOwnership = {
@@ -987,10 +920,6 @@ export class DummyERC721TokenContract extends BaseContract {
         > {
             const self = this as any as DummyERC721TokenContract;
             const functionSignature = 'transferOwnership(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [newOwner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [newOwner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([newOwner
         ]);
@@ -1004,7 +933,8 @@ export class DummyERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/erc20_proxy.ts b/packages/abi-gen-wrappers/src/generated-wrappers/erc20_proxy.ts
index dc47a116e..8f910eaf9 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/erc20_proxy.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/erc20_proxy.ts
@@ -94,10 +94,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'addAuthorizedAddress(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target
         ]);
@@ -111,7 +107,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public authorities = {
@@ -123,10 +120,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'authorities(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -140,8 +133,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public removeAuthorizedAddress = {
@@ -204,10 +197,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'removeAuthorizedAddress(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target
         ]);
@@ -221,7 +210,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public owner = {
@@ -232,8 +222,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'owner()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -246,8 +234,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public removeAuthorizedAddressAtIndex = {
@@ -318,12 +306,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'removeAuthorizedAddressAtIndex(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target,
-        index
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target,
-        index
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target,
         index
@@ -338,7 +320,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getProxyId = {
@@ -349,8 +332,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'getProxyId()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -363,8 +344,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public authorized = {
@@ -376,10 +357,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'authorized(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -393,8 +370,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getAuthorizedAddresses = {
@@ -405,8 +382,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'getAuthorizedAddresses()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -419,8 +394,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferOwnership = {
@@ -483,10 +458,6 @@ export class ERC20ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC20ProxyContract;
             const functionSignature = 'transferOwnership(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [newOwner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [newOwner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([newOwner
         ]);
@@ -500,7 +471,8 @@ export class ERC20ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/erc20_token.ts b/packages/abi-gen-wrappers/src/generated-wrappers/erc20_token.ts
index 83f5437df..b9aa50429 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/erc20_token.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/erc20_token.ts
@@ -104,12 +104,6 @@ export class ERC20TokenContract extends BaseContract {
         > {
             const self = this as any as ERC20TokenContract;
             const functionSignature = 'approve(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_spender,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_spender,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_spender,
         _value
@@ -124,8 +118,8 @@ export class ERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public totalSupply = {
@@ -136,8 +130,6 @@ export class ERC20TokenContract extends BaseContract {
         > {
             const self = this as any as ERC20TokenContract;
             const functionSignature = 'totalSupply()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -150,8 +142,8 @@ export class ERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferFrom = {
@@ -230,14 +222,6 @@ export class ERC20TokenContract extends BaseContract {
         > {
             const self = this as any as ERC20TokenContract;
             const functionSignature = 'transferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -253,8 +237,8 @@ export class ERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public balanceOf = {
@@ -266,10 +250,6 @@ export class ERC20TokenContract extends BaseContract {
         > {
             const self = this as any as ERC20TokenContract;
             const functionSignature = 'balanceOf(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner
         ]);
@@ -283,8 +263,8 @@ export class ERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transfer = {
@@ -355,12 +335,6 @@ export class ERC20TokenContract extends BaseContract {
         > {
             const self = this as any as ERC20TokenContract;
             const functionSignature = 'transfer(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_to,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_to,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_to,
         _value
@@ -375,8 +349,8 @@ export class ERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public allowance = {
@@ -389,12 +363,6 @@ export class ERC20TokenContract extends BaseContract {
         > {
             const self = this as any as ERC20TokenContract;
             const functionSignature = 'allowance(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner,
-        _spender
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner,
-        _spender
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner,
         _spender
@@ -409,8 +377,8 @@ export class ERC20TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/erc721_proxy.ts b/packages/abi-gen-wrappers/src/generated-wrappers/erc721_proxy.ts
index ae746d4d0..5ff11f35f 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/erc721_proxy.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/erc721_proxy.ts
@@ -94,10 +94,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'addAuthorizedAddress(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target
         ]);
@@ -111,7 +107,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public authorities = {
@@ -123,10 +120,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'authorities(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -140,8 +133,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public removeAuthorizedAddress = {
@@ -204,10 +197,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'removeAuthorizedAddress(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target
         ]);
@@ -221,7 +210,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public owner = {
@@ -232,8 +222,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'owner()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -246,8 +234,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public removeAuthorizedAddressAtIndex = {
@@ -318,12 +306,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'removeAuthorizedAddressAtIndex(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target,
-        index
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target,
-        index
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target,
         index
@@ -338,7 +320,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getProxyId = {
@@ -349,8 +332,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'getProxyId()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -363,8 +344,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public authorized = {
@@ -376,10 +357,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'authorized(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -393,8 +370,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getAuthorizedAddresses = {
@@ -405,8 +382,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'getAuthorizedAddresses()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -419,8 +394,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferOwnership = {
@@ -483,10 +458,6 @@ export class ERC721ProxyContract extends BaseContract {
         > {
             const self = this as any as ERC721ProxyContract;
             const functionSignature = 'transferOwnership(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [newOwner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [newOwner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([newOwner
         ]);
@@ -500,7 +471,8 @@ export class ERC721ProxyContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/erc721_token.ts b/packages/abi-gen-wrappers/src/generated-wrappers/erc721_token.ts
index 7205b7bf2..83951cef8 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/erc721_token.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/erc721_token.ts
@@ -53,10 +53,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'getApproved(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_tokenId
         ]);
@@ -70,8 +66,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public approve = {
@@ -142,12 +138,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'approve(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_approved,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_approved,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_approved,
         _tokenId
@@ -162,7 +152,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public transferFrom = {
@@ -241,14 +232,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'transferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -264,7 +247,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public safeTransferFrom1 = {
@@ -343,14 +327,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'safeTransferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -366,7 +342,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public ownerOf = {
@@ -378,10 +355,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'ownerOf(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_tokenId
         ]);
@@ -395,8 +368,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public balanceOf = {
@@ -408,10 +381,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'balanceOf(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner
         ]);
@@ -425,8 +394,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public setApprovalForAll = {
@@ -497,12 +466,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'setApprovalForAll(address,bool)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_operator,
-        _approved
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_operator,
-        _approved
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_operator,
         _approved
@@ -517,7 +480,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public safeTransferFrom2 = {
@@ -604,16 +568,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'safeTransferFrom(address,address,uint256,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _tokenId,
-        _data
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _tokenId,
-        _data
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -630,7 +584,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public isApprovedForAll = {
@@ -643,12 +598,6 @@ export class ERC721TokenContract extends BaseContract {
         > {
             const self = this as any as ERC721TokenContract;
             const functionSignature = 'isApprovedForAll(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner,
-        _operator
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner,
-        _operator
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner,
         _operator
@@ -663,8 +612,8 @@ export class ERC721TokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/exchange.ts b/packages/abi-gen-wrappers/src/generated-wrappers/exchange.ts
index e7abd970c..f4cdeaaf9 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/exchange.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/exchange.ts
@@ -79,10 +79,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'filled(bytes32)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -96,8 +92,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public batchFillOrders = {
@@ -176,14 +172,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'batchFillOrders((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256[],bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        takerAssetFillAmounts,
-        signatures
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        takerAssetFillAmounts,
-        signatures
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         takerAssetFillAmounts,
@@ -199,8 +187,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public cancelled = {
@@ -212,10 +200,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'cancelled(bytes32)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -229,8 +213,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public preSign = {
@@ -309,14 +293,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'preSign(bytes32,address,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [hash,
-        signerAddress,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [hash,
-        signerAddress,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([hash,
         signerAddress,
@@ -332,7 +308,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public matchOrders = {
@@ -419,16 +396,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'matchOrders((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes),(address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes),bytes,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [leftOrder,
-        rightOrder,
-        leftSignature,
-        rightSignature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [leftOrder,
-        rightOrder,
-        leftSignature,
-        rightSignature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([leftOrder,
         rightOrder,
@@ -445,8 +412,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public fillOrderNoThrow = {
@@ -525,14 +492,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'fillOrderNoThrow((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes),uint256,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [order,
-        takerAssetFillAmount,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [order,
-        takerAssetFillAmount,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([order,
         takerAssetFillAmount,
@@ -548,8 +507,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public assetProxies = {
@@ -561,10 +520,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'assetProxies(bytes4)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -578,8 +533,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public batchCancelOrders = {
@@ -642,10 +597,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'batchCancelOrders((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders
         ]);
@@ -659,7 +610,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public batchFillOrKillOrders = {
@@ -738,14 +690,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'batchFillOrKillOrders((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256[],bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        takerAssetFillAmounts,
-        signatures
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        takerAssetFillAmounts,
-        signatures
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         takerAssetFillAmounts,
@@ -761,8 +705,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public cancelOrdersUpTo = {
@@ -825,10 +769,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'cancelOrdersUpTo(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [targetOrderEpoch
-        ] = BaseContract._formatABIDataItemList(inputAbi, [targetOrderEpoch
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([targetOrderEpoch
         ]);
@@ -842,7 +782,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public batchFillOrdersNoThrow = {
@@ -921,14 +862,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'batchFillOrdersNoThrow((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256[],bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        takerAssetFillAmounts,
-        signatures
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        takerAssetFillAmounts,
-        signatures
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         takerAssetFillAmounts,
@@ -944,8 +877,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getAssetProxy = {
@@ -957,10 +890,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'getAssetProxy(bytes4)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [assetProxyId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [assetProxyId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([assetProxyId
         ]);
@@ -974,8 +903,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transactions = {
@@ -987,10 +916,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'transactions(bytes32)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -1004,8 +929,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public fillOrKillOrder = {
@@ -1084,14 +1009,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'fillOrKillOrder((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes),uint256,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [order,
-        takerAssetFillAmount,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [order,
-        takerAssetFillAmount,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([order,
         takerAssetFillAmount,
@@ -1107,8 +1024,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public setSignatureValidatorApproval = {
@@ -1179,12 +1096,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'setSignatureValidatorApproval(address,bool)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [validatorAddress,
-        approval
-        ] = BaseContract._formatABIDataItemList(inputAbi, [validatorAddress,
-        approval
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([validatorAddress,
         approval
@@ -1199,7 +1110,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public allowedValidators = {
@@ -1212,12 +1124,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'allowedValidators(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0,
-        index_1
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0,
-        index_1
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0,
         index_1
@@ -1232,8 +1138,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public marketSellOrders = {
@@ -1312,14 +1218,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'marketSellOrders((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256,bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        takerAssetFillAmount,
-        signatures
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        takerAssetFillAmount,
-        signatures
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         takerAssetFillAmount,
@@ -1335,8 +1233,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getOrdersInfo = {
@@ -1348,10 +1246,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'getOrdersInfo((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders
         ]);
@@ -1365,8 +1259,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public preSigned = {
@@ -1379,12 +1273,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'preSigned(bytes32,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0,
-        index_1
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0,
-        index_1
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0,
         index_1
@@ -1399,8 +1287,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public owner = {
@@ -1411,8 +1299,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'owner()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -1425,8 +1311,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public isValidSignature = {
@@ -1440,14 +1326,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'isValidSignature(bytes32,address,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [hash,
-        signerAddress,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [hash,
-        signerAddress,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([hash,
         signerAddress,
@@ -1463,8 +1341,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public marketBuyOrdersNoThrow = {
@@ -1543,14 +1421,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'marketBuyOrdersNoThrow((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256,bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        makerAssetFillAmount,
-        signatures
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        makerAssetFillAmount,
-        signatures
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         makerAssetFillAmount,
@@ -1566,8 +1436,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public fillOrder = {
@@ -1646,14 +1516,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'fillOrder((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes),uint256,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [order,
-        takerAssetFillAmount,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [order,
-        takerAssetFillAmount,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([order,
         takerAssetFillAmount,
@@ -1669,8 +1531,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public executeTransaction = {
@@ -1757,16 +1619,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'executeTransaction(uint256,address,bytes,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [salt,
-        signerAddress,
-        data,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [salt,
-        signerAddress,
-        data,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([salt,
         signerAddress,
@@ -1783,7 +1635,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public registerAssetProxy = {
@@ -1846,10 +1699,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'registerAssetProxy(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [assetProxy
-        ] = BaseContract._formatABIDataItemList(inputAbi, [assetProxy
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([assetProxy
         ]);
@@ -1863,7 +1712,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getOrderInfo = {
@@ -1875,10 +1725,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'getOrderInfo((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes))';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [order
-        ] = BaseContract._formatABIDataItemList(inputAbi, [order
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([order
         ]);
@@ -1892,8 +1738,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public cancelOrder = {
@@ -1956,10 +1802,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'cancelOrder((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes))';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [order
-        ] = BaseContract._formatABIDataItemList(inputAbi, [order
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([order
         ]);
@@ -1973,7 +1815,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public orderEpoch = {
@@ -1986,12 +1829,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'orderEpoch(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0,
-        index_1
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0,
-        index_1
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0,
         index_1
@@ -2006,8 +1843,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public ZRX_ASSET_DATA = {
@@ -2018,8 +1855,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'ZRX_ASSET_DATA()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -2032,8 +1867,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public marketSellOrdersNoThrow = {
@@ -2112,14 +1947,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'marketSellOrdersNoThrow((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256,bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        takerAssetFillAmount,
-        signatures
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        takerAssetFillAmount,
-        signatures
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         takerAssetFillAmount,
@@ -2135,8 +1962,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public EIP712_DOMAIN_HASH = {
@@ -2147,8 +1974,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'EIP712_DOMAIN_HASH()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -2161,8 +1986,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public marketBuyOrders = {
@@ -2241,14 +2066,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'marketBuyOrders((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256,bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        makerAssetFillAmount,
-        signatures
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        makerAssetFillAmount,
-        signatures
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         makerAssetFillAmount,
@@ -2264,8 +2081,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public currentContextAddress = {
@@ -2276,8 +2093,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'currentContextAddress()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -2290,8 +2105,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferOwnership = {
@@ -2354,10 +2169,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'transferOwnership(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [newOwner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [newOwner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([newOwner
         ]);
@@ -2371,7 +2182,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public VERSION = {
@@ -2382,8 +2194,6 @@ export class ExchangeContract extends BaseContract {
         > {
             const self = this as any as ExchangeContract;
             const functionSignature = 'VERSION()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -2396,8 +2206,8 @@ export class ExchangeContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/forwarder.ts b/packages/abi-gen-wrappers/src/generated-wrappers/forwarder.ts
index c2f7835eb..d0797eccd 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/forwarder.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/forwarder.ts
@@ -123,22 +123,6 @@ export class ForwarderContract extends BaseContract {
         > {
             const self = this as any as ForwarderContract;
             const functionSignature = 'marketBuyOrdersWithEth((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],uint256,bytes[],(address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],bytes[],uint256,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        makerAssetFillAmount,
-        signatures,
-        feeOrders,
-        feeSignatures,
-        feePercentage,
-        feeRecipient
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        makerAssetFillAmount,
-        signatures,
-        feeOrders,
-        feeSignatures,
-        feePercentage,
-        feeRecipient
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         makerAssetFillAmount,
@@ -158,8 +142,8 @@ export class ForwarderContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public withdrawAsset = {
@@ -230,12 +214,6 @@ export class ForwarderContract extends BaseContract {
         > {
             const self = this as any as ForwarderContract;
             const functionSignature = 'withdrawAsset(bytes,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [assetData,
-        amount
-        ] = BaseContract._formatABIDataItemList(inputAbi, [assetData,
-        amount
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([assetData,
         amount
@@ -250,7 +228,8 @@ export class ForwarderContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public owner = {
@@ -261,8 +240,6 @@ export class ForwarderContract extends BaseContract {
         > {
             const self = this as any as ForwarderContract;
             const functionSignature = 'owner()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -275,8 +252,8 @@ export class ForwarderContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public marketSellOrdersWithEth = {
@@ -379,20 +356,6 @@ export class ForwarderContract extends BaseContract {
         > {
             const self = this as any as ForwarderContract;
             const functionSignature = 'marketSellOrdersWithEth((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],bytes[],(address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],bytes[],uint256,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        signatures,
-        feeOrders,
-        feeSignatures,
-        feePercentage,
-        feeRecipient
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        signatures,
-        feeOrders,
-        feeSignatures,
-        feePercentage,
-        feeRecipient
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         signatures,
@@ -411,8 +374,8 @@ export class ForwarderContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public transferOwnership = {
@@ -475,10 +438,6 @@ export class ForwarderContract extends BaseContract {
         > {
             const self = this as any as ForwarderContract;
             const functionSignature = 'transferOwnership(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [newOwner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [newOwner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([newOwner
         ]);
@@ -492,7 +451,8 @@ export class ForwarderContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts b/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts
index 60423a0b9..cabaeeb98 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/i_validator.ts
@@ -26,14 +26,6 @@ export class IValidatorContract extends BaseContract {
         > {
             const self = this as any as IValidatorContract;
             const functionSignature = 'isValidSignature(bytes32,address,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [hash,
-        signerAddress,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [hash,
-        signerAddress,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([hash,
         signerAddress,
@@ -49,8 +41,8 @@ export class IValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts b/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts
index 5e70cedad..9d54ca0c1 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/i_wallet.ts
@@ -25,12 +25,6 @@ export class IWalletContract extends BaseContract {
         > {
             const self = this as any as IWalletContract;
             const functionSignature = 'isValidSignature(bytes32,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [hash,
-        signature
-        ] = BaseContract._formatABIDataItemList(inputAbi, [hash,
-        signature
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([hash,
         signature
@@ -45,8 +39,8 @@ export class IWalletContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/order_validator.ts b/packages/abi-gen-wrappers/src/generated-wrappers/order_validator.ts
index b1d0d3be5..5740af4ab 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/order_validator.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/order_validator.ts
@@ -25,12 +25,6 @@ export class OrderValidatorContract extends BaseContract {
         > {
             const self = this as any as OrderValidatorContract;
             const functionSignature = 'getOrderAndTraderInfo((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes),address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [order,
-        takerAddress
-        ] = BaseContract._formatABIDataItemList(inputAbi, [order,
-        takerAddress
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([order,
         takerAddress
@@ -45,8 +39,8 @@ export class OrderValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getBalanceAndAllowance = {
@@ -59,12 +53,6 @@ export class OrderValidatorContract extends BaseContract {
         > {
             const self = this as any as OrderValidatorContract;
             const functionSignature = 'getBalanceAndAllowance(address,bytes)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target,
-        assetData
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target,
-        assetData
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target,
         assetData
@@ -79,8 +67,8 @@ export class OrderValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getOrdersAndTradersInfo = {
@@ -93,12 +81,6 @@ export class OrderValidatorContract extends BaseContract {
         > {
             const self = this as any as OrderValidatorContract;
             const functionSignature = 'getOrdersAndTradersInfo((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],address[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        takerAddresses
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        takerAddresses
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         takerAddresses
@@ -113,8 +95,8 @@ export class OrderValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getTradersInfo = {
@@ -127,12 +109,6 @@ export class OrderValidatorContract extends BaseContract {
         > {
             const self = this as any as OrderValidatorContract;
             const functionSignature = 'getTradersInfo((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes)[],address[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [orders,
-        takerAddresses
-        ] = BaseContract._formatABIDataItemList(inputAbi, [orders,
-        takerAddresses
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([orders,
         takerAddresses
@@ -147,8 +123,8 @@ export class OrderValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getERC721TokenOwner = {
@@ -161,12 +137,6 @@ export class OrderValidatorContract extends BaseContract {
         > {
             const self = this as any as OrderValidatorContract;
             const functionSignature = 'getERC721TokenOwner(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [token,
-        tokenId
-        ] = BaseContract._formatABIDataItemList(inputAbi, [token,
-        tokenId
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([token,
         tokenId
@@ -181,8 +151,8 @@ export class OrderValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public getBalancesAndAllowances = {
@@ -195,12 +165,6 @@ export class OrderValidatorContract extends BaseContract {
         > {
             const self = this as any as OrderValidatorContract;
             const functionSignature = 'getBalancesAndAllowances(address,bytes[])';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [target,
-        assetData
-        ] = BaseContract._formatABIDataItemList(inputAbi, [target,
-        assetData
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([target,
         assetData
@@ -215,8 +179,8 @@ export class OrderValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public getTraderInfo = {
@@ -229,12 +193,6 @@ export class OrderValidatorContract extends BaseContract {
         > {
             const self = this as any as OrderValidatorContract;
             const functionSignature = 'getTraderInfo((address,address,address,address,uint256,uint256,uint256,uint256,uint256,uint256,bytes,bytes),address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [order,
-        takerAddress
-        ] = BaseContract._formatABIDataItemList(inputAbi, [order,
-        takerAddress
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([order,
         takerAddress
@@ -249,8 +207,8 @@ export class OrderValidatorContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/weth9.ts b/packages/abi-gen-wrappers/src/generated-wrappers/weth9.ts
index ed590d3ca..773ecb9d3 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/weth9.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/weth9.ts
@@ -58,8 +58,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'name()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -72,8 +70,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public approve = {
@@ -144,12 +142,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'approve(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [guy,
-        wad
-        ] = BaseContract._formatABIDataItemList(inputAbi, [guy,
-        wad
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([guy,
         wad
@@ -164,8 +156,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public totalSupply = {
@@ -176,8 +168,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'totalSupply()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -190,8 +180,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferFrom = {
@@ -270,14 +260,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'transferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [src,
-        dst,
-        wad
-        ] = BaseContract._formatABIDataItemList(inputAbi, [src,
-        dst,
-        wad
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([src,
         dst,
@@ -293,8 +275,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public withdraw = {
@@ -357,10 +339,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'withdraw(uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [wad
-        ] = BaseContract._formatABIDataItemList(inputAbi, [wad
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([wad
         ]);
@@ -374,7 +352,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public decimals = {
@@ -385,8 +364,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'decimals()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -399,8 +376,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public balanceOf = {
@@ -412,10 +389,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'balanceOf(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0
         ]);
@@ -429,8 +402,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public symbol = {
@@ -441,8 +414,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'symbol()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -455,8 +426,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transfer = {
@@ -527,12 +498,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'transfer(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [dst,
-        wad
-        ] = BaseContract._formatABIDataItemList(inputAbi, [dst,
-        wad
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([dst,
         wad
@@ -547,8 +512,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public deposit = {
@@ -603,8 +568,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'deposit()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -617,7 +580,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                return;
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray;
         },
     };
     public allowance = {
@@ -630,12 +594,6 @@ export class WETH9Contract extends BaseContract {
         > {
             const self = this as any as WETH9Contract;
             const functionSignature = 'allowance(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [index_0,
-        index_1
-        ] = BaseContract._formatABIDataItemList(inputAbi, [index_0,
-        index_1
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([index_0,
         index_1
@@ -650,8 +608,8 @@ export class WETH9Contract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/abi-gen-wrappers/src/generated-wrappers/zrx_token.ts b/packages/abi-gen-wrappers/src/generated-wrappers/zrx_token.ts
index 026a25165..afa80f368 100644
--- a/packages/abi-gen-wrappers/src/generated-wrappers/zrx_token.ts
+++ b/packages/abi-gen-wrappers/src/generated-wrappers/zrx_token.ts
@@ -44,8 +44,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'name()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -58,8 +56,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public approve = {
@@ -130,12 +128,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'approve(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_spender,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_spender,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_spender,
         _value
@@ -150,8 +142,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public totalSupply = {
@@ -162,8 +154,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'totalSupply()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -176,8 +166,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transferFrom = {
@@ -256,14 +246,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'transferFrom(address,address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_from,
-        _to,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_from,
-        _to,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_from,
         _to,
@@ -279,8 +261,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public decimals = {
@@ -291,8 +273,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'decimals()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -305,8 +285,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public balanceOf = {
@@ -318,10 +298,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'balanceOf(address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner
         ]);
@@ -335,8 +311,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public symbol = {
@@ -347,8 +323,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'symbol()';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [] = BaseContract._formatABIDataItemList(inputAbi, [], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([]);
             const callDataWithDefaults = await BaseContract._applyDefaultsToTxDataAsync(
@@ -361,8 +335,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public transfer = {
@@ -433,12 +407,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'transfer(address,uint256)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_to,
-        _value
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_to,
-        _value
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_to,
         _value
@@ -453,8 +421,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public allowance = {
@@ -467,12 +435,6 @@ export class ZRXTokenContract extends BaseContract {
         > {
             const self = this as any as ZRXTokenContract;
             const functionSignature = 'allowance(address,address)';
-            const inputAbi = self._lookupAbi(functionSignature).inputs;
-            [_owner,
-        _spender
-        ] = BaseContract._formatABIDataItemList(inputAbi, [_owner,
-        _spender
-        ], BaseContract._bigNumberToString.bind(self));
             const abiEncoder = self._lookupAbiEncoder(functionSignature);
             const encodedData = abiEncoder.encode([_owner,
         _spender
@@ -487,8 +449,8 @@ export class ZRXTokenContract extends BaseContract {
             );
             const rawCallResult = await self._web3Wrapper.callAsync(callDataWithDefaults, defaultBlock);
             BaseContract._throwIfRevertWithReasonCallResult(rawCallResult);
-                let resultArray = abiEncoder.decodeReturnValuesAsArray(rawCallResult, {structsAsObjects: true});
-                return resultArray[0];
+            let resultArray = abiEncoder.decodeReturnValuesAsArrayOrNull(rawCallResult);
+            return resultArray[0];
         },
     };
     public static async deployFrom0xArtifactAsync(
diff --git a/packages/utils/src/abi_encoder/evm_data_types/method.ts b/packages/utils/src/abi_encoder/evm_data_types/method.ts
index c777902e8..bae0fdb5d 100644
--- a/packages/utils/src/abi_encoder/evm_data_types/method.ts
+++ b/packages/utils/src/abi_encoder/evm_data_types/method.ts
@@ -51,6 +51,12 @@ export class MethodDataType extends AbstractSetDataType {
         return returnValuesAsArray;
     }
 
+    public decodeReturnValuesAsArrayOrNull(returndata: string, rules?: DecodingRules): any {
+        const returnValuesAsArray = this.decodeReturnValuesAsArray(returndata, rules);
+        const returnValue = _.isEmpty(returnValuesAsArray) ? [] : returnValuesAsArray;
+        return returnValue;
+    }
+
     public getSignature(): string {
         return this._methodSignature;
     }