Add check for ROUNDING_ERROR and test for it

2 files changed, 21 insertions, 0 deletions

diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index 3fb187de2..fe5fc3d78 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -154,6 +154,10 @@ export class ExchangeWrapper extends ContractWrapper {
         if (fillMakerAmountInBaseUnits.greaterThan(makerAllowance)) {
             throw new Error(FillOrderValidationErrs.NOT_ENOUGH_MAKER_ALLOWANCE);
         }
+        if (await this.isRoundingErrorAsync(signedOrder.takerTokenAmount, fillTakerAmountInBaseUnits,
+                                            signedOrder.makerTokenAmount)) {
+            throw new Error(FillOrderValidationErrs.ROUNDING_ERROR);
+        }
     }
     private throwErrorLogsAsErrors(logs: ContractEvent[]): void {
         const errEvent = _.find(logs, {event: 'LogError'});
@@ -163,6 +167,18 @@ export class ExchangeWrapper extends ContractWrapper {
             throw new Error(errMessage);
         }
     }
+    private async isRoundingErrorAsync(takerTokenAmount: BigNumber.BigNumber,
+                                       fillTakerAmountInBaseUnits: BigNumber.BigNumber,
+                                       makerTokenAmount: BigNumber.BigNumber): Promise<boolean> {
+        const exchangeInstance = await this.getExchangeContractAsync();
+        const senderAddress = await this.web3Wrapper.getSenderAddressOrThrowAsync();
+        const isRoundingError = await exchangeInstance.isRoundingError.call(
+            takerTokenAmount, fillTakerAmountInBaseUnits, makerTokenAmount, {
+                from: senderAddress,
+            },
+        );
+        return isRoundingError;
+    }
     private async getExchangeContractAsync(): Promise<ExchangeContract> {
         if (!_.isUndefined(this.exchangeContractIfExists)) {
             return this.exchangeContractIfExists;
diff --git a/src/types.ts b/src/types.ts
index f80f98dc4..73c448b85 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -34,6 +34,10 @@ export type OrderValues = [BigNumber.BigNumber, BigNumber.BigNumber, BigNumber.B
 
 export interface ExchangeContract {
     isValidSignature: any;
+    isRoundingError: {
+        call: (takerTokenAmount: BigNumber.BigNumber, fillTakerAmountInBaseUnits: BigNumber.BigNumber,
+               makerTokenAmount: BigNumber.BigNumber, txOpts: TxOpts) => Promise<boolean>;
+    };
     fill: {
         (orderAddresses: OrderAddresses, orderValues: OrderValues, fillAmount: BigNumber.BigNumber,
          shouldCheckTransfer: boolean, v: number, r: string, s: string, txOpts: TxOpts): ContractResponse;
@@ -93,6 +97,7 @@ export const FillOrderValidationErrs = strEnum([
     'NOT_ENOUGH_TAKER_ALLOWANCE',
     'NOT_ENOUGH_MAKER_BALANCE',
     'NOT_ENOUGH_MAKER_ALLOWANCE',
+    'ROUNDING_ERROR',
 ]);
 export type FillOrderValidationErrs = keyof typeof FillOrderValidationErrs;