7 files changed, 74 insertions, 9 deletions

diff --git a/src/0x.js.ts b/src/0x.js.ts
index f3da005f8..4c67027fc 100644
--- a/src/0x.js.ts
+++ b/src/0x.js.ts
@@ -137,6 +137,15 @@ export class ZeroEx {
         this.tokenRegistry = new TokenRegistryWrapper(this.web3Wrapper);
     }
     /**
+     * Sets a new provider for the web3 instance used by 0x.js internally and invalidates any instantiated
+     * contract instances instantiated with the old provider.
+     */
+    public setProvider(provider: Web3.Provider) {
+        this.web3Wrapper.setProvider(provider);
+        this.exchange.invalidateContractInstance();
+        this.tokenRegistry.invalidateContractInstance();
+    }
+    /**
      * Signs an orderHash and returns it's elliptic curve signature
      * This method currently supports TestRPC, Geth and Parity above and below V1.6.6
      */
diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index f0f153c2b..3f6eb0dab 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -7,9 +7,13 @@ import * as ExchangeArtifacts from '../artifacts/Exchange.json';
 import {ecSignatureSchema} from '../schemas/ec_signature_schema';
 
 export class ExchangeWrapper extends ContractWrapper {
+    private exchangeContractIfExists?: ExchangeContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
+    public invalidateContractInstance(): void {
+        delete this.exchangeContractIfExists;
+    }
     public async isValidSignatureAsync(dataHex: string, ecSignature: ECSignature,
                                        signerAddressHex: string): Promise<boolean> {
         assert.isHexString('dataHex', dataHex);
@@ -19,10 +23,9 @@ export class ExchangeWrapper extends ContractWrapper {
         const senderAddressIfExists = await this.web3Wrapper.getSenderAddressIfExistsAsync();
         assert.assert(!_.isUndefined(senderAddressIfExists), ZeroExError.USER_HAS_NO_ASSOCIATED_ADDRESSES);
 
-        const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
-        const exchangeInstance = contractInstance as ExchangeContract;
+        const exchangeContract = await this.getExchangeContractAsync();
 
-        const isValidSignature = await exchangeInstance.isValidSignature.call(
+        const isValidSignature = await exchangeContract.isValidSignature.call(
             signerAddressHex,
             dataHex,
             ecSignature.v,
@@ -34,4 +37,12 @@ export class ExchangeWrapper extends ContractWrapper {
         );
         return isValidSignature;
     }
+    private async getExchangeContractAsync(): Promise<ExchangeContract> {
+        if (!_.isUndefined(this.exchangeContractIfExists)) {
+            return this.exchangeContractIfExists;
+        }
+        const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
+        this.exchangeContractIfExists = contractInstance as ExchangeContract;
+        return this.exchangeContractIfExists;
+    }
 }
diff --git a/src/contract_wrappers/token_registry_wrapper.ts b/src/contract_wrappers/token_registry_wrapper.ts
index 8dd79171e..86bea1c5d 100644
--- a/src/contract_wrappers/token_registry_wrapper.ts
+++ b/src/contract_wrappers/token_registry_wrapper.ts
@@ -6,12 +6,15 @@ import {ContractWrapper} from './contract_wrapper';
 import * as TokenRegistryArtifacts from '../artifacts/TokenRegistry.json';
 
 export class TokenRegistryWrapper extends ContractWrapper {
+    private tokenRegistryContractIfExists?: TokenRegistryContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
+    public invalidateContractInstance(): void {
+        delete this.tokenRegistryContractIfExists;
+    }
     public async getTokensAsync(): Promise<Token[]> {
-        const contractInstance = await this.instantiateContractIfExistsAsync((TokenRegistryArtifacts as any));
-        const tokenRegistryContract = contractInstance as TokenRegistryContract;
+        const tokenRegistryContract = await this.getTokenRegistryContractAsync();
 
         const addresses = await tokenRegistryContract.getTokenAddresses.call();
         const tokenMetadataPromises: Array<Promise<TokenMetadata>> = _.map(
@@ -30,4 +33,12 @@ export class TokenRegistryWrapper extends ContractWrapper {
         });
         return tokens;
     }
+    private async getTokenRegistryContractAsync(): Promise<TokenRegistryContract> {
+        if (!_.isUndefined(this.tokenRegistryContractIfExists)) {
+            return this.tokenRegistryContractIfExists;
+        }
+        const contractInstance = await this.instantiateContractIfExistsAsync((TokenRegistryArtifacts as any));
+        this.tokenRegistryContractIfExists = contractInstance as TokenRegistryContract;
+        return this.tokenRegistryContractIfExists;
+    }
 }
diff --git a/src/web3_wrapper.ts b/src/web3_wrapper.ts
index a915a89e8..e65f29b56 100644
--- a/src/web3_wrapper.ts
+++ b/src/web3_wrapper.ts
@@ -9,6 +9,9 @@ export class Web3Wrapper {
         this.web3 = new Web3();
         this.web3.setProvider(web3.currentProvider);
     }
+    public setProvider(provider: Web3.Provider) {
+        this.web3.setProvider(provider);
+    }
     public isAddress(address: string): boolean {
         return this.web3.isAddress(address);
     }
diff --git a/test/0x.js_test.ts b/test/0x.js_test.ts
index c45c70991..5d23d7094 100644
--- a/test/0x.js_test.ts
+++ b/test/0x.js_test.ts
@@ -13,6 +13,34 @@ chai.use(ChaiBigNumber());
 const expect = chai.expect;
 
 describe('ZeroEx library', () => {
+    describe('#setProvider', () => {
+        it('overrides the provider in the nested web3 instance and invalidates contractInstances', async () => {
+            const web3 = web3Factory.create();
+            const zeroEx = new ZeroEx(web3);
+            // Instantiate the contract instances with the current provider
+            await (zeroEx.exchange as any).getExchangeContractAsync();
+            await (zeroEx.tokenRegistry as any).getTokenRegistryContractAsync();
+            expect((zeroEx.exchange as any).exchangeContractIfExists).to.not.be.undefined;
+            expect((zeroEx.tokenRegistry as any).tokenRegistryContractIfExists).to.not.be.undefined;
+
+            const newProvider = web3Factory.getRpcProvider();
+            // Add property to newProvider so that we can differentiate it from old provider
+            (newProvider as any).zeroExTestId = 1;
+            zeroEx.setProvider(newProvider);
+
+            // Check that contractInstances with old provider are removed after provider update
+            expect((zeroEx.exchange as any).exchangeContractIfExists).to.be.undefined;
+            expect((zeroEx.tokenRegistry as any).tokenRegistryContractIfExists).to.be.undefined;
+
+            // Check that all nested web3 instances return the updated provider
+            const nestedWeb3WrapperProvider = (zeroEx as any).web3Wrapper.getCurrentProvider();
+            expect((nestedWeb3WrapperProvider as any).zeroExTestId).to.be.a('number');
+            const exchangeWeb3WrapperProvider = zeroEx.exchange.web3Wrapper.getCurrentProvider();
+            expect((exchangeWeb3WrapperProvider as any).zeroExTestId).to.be.a('number');
+            const tokenRegistryWeb3WrapperProvider = zeroEx.tokenRegistry.web3Wrapper.getCurrentProvider();
+            expect((tokenRegistryWeb3WrapperProvider as any).zeroExTestId).to.be.a('number');
+        });
+    });
     describe('#getOrderHash', () => {
         const expectedOrderHash = '0x103a5e97dab5dbeb8f385636f86a7d1e458a7ccbe1bd194727f0b2f85ab116c7';
         it('defaults takerAddress to NULL address', () => {
diff --git a/test/exchange_wrapper.ts b/test/exchange_wrapper.ts
index 4bfc49374..55b84ce36 100644
--- a/test/exchange_wrapper.ts
+++ b/test/exchange_wrapper.ts
@@ -1,7 +1,6 @@
 import 'mocha';
 import * as chai from 'chai';
 import chaiAsPromised = require('chai-as-promised');
-import * as Web3 from 'web3';
 import {web3Factory} from './utils/web3_factory';
 import {ZeroEx} from '../src/0x.js';
 import {BlockchainLifecycle} from './utils/blockchain_lifecycle';
diff --git a/test/utils/web3_factory.ts b/test/utils/web3_factory.ts
index 493fbc2df..ffdc0e4cf 100644
--- a/test/utils/web3_factory.ts
+++ b/test/utils/web3_factory.ts
@@ -10,14 +10,18 @@ import {constants} from './constants';
 
 export const web3Factory = {
     create(): Web3 {
+        const provider = this.getRpcProvider();
+        const web3 = new Web3();
+        web3.setProvider(provider);
+        return web3;
+    },
+    getRpcProvider(): Web3.Provider {
         const provider = new ProviderEngine();
         const rpcUrl = `http://${constants.RPC_HOST}:${constants.RPC_PORT}`;
         provider.addProvider(new RpcSubprovider({
             rpcUrl,
         }));
         provider.start();
-        const web3 = new Web3();
-        web3.setProvider(provider);
-        return web3;
+        return provider;
     },
 };