feat(asset-buyer): Custom InsufficientAssetLiquidityError error

BREAKING CHANGE: A custom InsufficientAssetLiquidityError error is now raised when there is insufficient liquidity

4 files changed, 107 insertions, 9 deletions

diff --git a/packages/asset-buyer/src/types.ts b/packages/asset-buyer/src/types.ts
index 3b573edca..dfa17a22d 100644
--- a/packages/asset-buyer/src/types.ts
+++ b/packages/asset-buyer/src/types.ts
@@ -117,6 +117,16 @@ export enum AssetBuyerError {
     TransactionValueTooLow = 'TRANSACTION_VALUE_TOO_LOW',
 }
 
+export class InsufficientAssetLiquidityError extends Error {
+    public numAssetsAvailable: BigNumber;
+    constructor(numAssetsAvailable: BigNumber) {
+        super(AssetBuyerError.InsufficientAssetLiquidity);
+        this.numAssetsAvailable = numAssetsAvailable;
+        // Setting prototype so instanceof works.  See https://github.com/Microsoft/TypeScript/wiki/Breaking-Changes#extending-built-ins-like-error-array-and-map-may-no-longer-work
+        Object.setPrototypeOf(this, InsufficientAssetLiquidityError.prototype);
+    }
+}
+
 export interface OrdersAndFillableAmounts {
     orders: SignedOrder[];
     remainingFillableMakerAssetAmounts: BigNumber[];
diff --git a/packages/asset-buyer/src/utils/buy_quote_calculator.ts b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
index b15b880c2..e52c9c5bf 100644
--- a/packages/asset-buyer/src/utils/buy_quote_calculator.ts
+++ b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
@@ -3,7 +3,13 @@ import { BigNumber } from '@0x/utils';
 import * as _ from 'lodash';
 
 import { constants } from '../constants';
-import { AssetBuyerError, BuyQuote, BuyQuoteInfo, OrdersAndFillableAmounts } from '../types';
+import {
+    AssetBuyerError,
+    BuyQuote,
+    BuyQuoteInfo,
+    InsufficientAssetLiquidityError,
+    OrdersAndFillableAmounts,
+} from '../types';
 
 import { orderUtils } from './order_utils';
 
@@ -33,7 +39,8 @@ export const buyQuoteCalculator = {
         });
         // if we do not have enough orders to cover the desired assetBuyAmount, throw
         if (remainingFillAmount.gt(constants.ZERO_AMOUNT)) {
-            throw new Error(AssetBuyerError.InsufficientAssetLiquidity);
+            const amountRemaining = assetBuyAmount.minus(remainingFillAmount);
+            throw new InsufficientAssetLiquidityError(amountRemaining);
         }
         // if we are not buying ZRX:
         // given the orders calculated above, find the fee-orders that cover the desired assetBuyAmount (with slippage)
diff --git a/packages/asset-buyer/test/buy_quote_calculator_test.ts b/packages/asset-buyer/test/buy_quote_calculator_test.ts
index a30017b72..1dd829a0f 100644
--- a/packages/asset-buyer/test/buy_quote_calculator_test.ts
+++ b/packages/asset-buyer/test/buy_quote_calculator_test.ts
@@ -1,4 +1,5 @@
 import { orderFactory } from '@0x/order-utils/lib/src/order_factory';
+import { SignedOrder } from '@0x/types';
 import { BigNumber } from '@0x/utils';
 import * as chai from 'chai';
 import * as _ from 'lodash';
@@ -8,6 +9,7 @@ import { AssetBuyerError, OrdersAndFillableAmounts } from '../src/types';
 import { buyQuoteCalculator } from '../src/utils/buy_quote_calculator';
 
 import { chaiSetup } from './utils/chai_setup';
+import { testHelpers } from './utils/test_helpers';
 
 chaiSetup.configure();
 const expect = chai.expect;
@@ -15,6 +17,10 @@ const expect = chai.expect;
 // tslint:disable:custom-no-magic-numbers
 describe('buyQuoteCalculator', () => {
     describe('#calculate', () => {
+        let firstOrder: SignedOrder;
+        let firstRemainingFillAmount: BigNumber;
+        let secondOrder: SignedOrder;
+        let secondRemainingFillAmount: BigNumber;
         let ordersAndFillableAmounts: OrdersAndFillableAmounts;
         let smallFeeOrderAndFillableAmount: OrdersAndFillableAmounts;
         let allFeeOrdersAndFillableAmounts: OrdersAndFillableAmounts;
@@ -24,18 +30,18 @@ describe('buyQuoteCalculator', () => {
             // the second order has a rate of 2 makerAsset / WETH with a takerFee of 100 ZRX and has 200 / 200 makerAsset units left to fill (completely fillable)
             // generate one order for fees
             // the fee order has a rate of 1 ZRX / WETH with no taker fee and has 100 ZRX left to fill (completely fillable)
-            const firstOrder = orderFactory.createSignedOrderFromPartial({
+            firstOrder = orderFactory.createSignedOrderFromPartial({
                 makerAssetAmount: new BigNumber(400),
                 takerAssetAmount: new BigNumber(100),
                 takerFee: new BigNumber(200),
             });
-            const firstRemainingFillAmount = new BigNumber(200);
-            const secondOrder = orderFactory.createSignedOrderFromPartial({
+            firstRemainingFillAmount = new BigNumber(200);
+            secondOrder = orderFactory.createSignedOrderFromPartial({
                 makerAssetAmount: new BigNumber(200),
                 takerAssetAmount: new BigNumber(100),
                 takerFee: new BigNumber(100),
             });
-            const secondRemainingFillAmount = secondOrder.makerAssetAmount;
+            secondRemainingFillAmount = secondOrder.makerAssetAmount;
             ordersAndFillableAmounts = {
                 orders: [firstOrder, secondOrder],
                 remainingFillableMakerAssetAmounts: [firstRemainingFillAmount, secondRemainingFillAmount],
@@ -61,9 +67,9 @@ describe('buyQuoteCalculator', () => {
                 ],
             };
         });
-        it('should throw if not enough maker asset liquidity', () => {
+        it('should throw if not enough maker asset liquidity (multiple orders)', () => {
             // we have 400 makerAsset units available to fill but attempt to calculate a quote for 500 makerAsset units
-            expect(() =>
+            const errorFunction = () => {
                 buyQuoteCalculator.calculate(
                     ordersAndFillableAmounts,
                     smallFeeOrderAndFillableAmount,
@@ -71,8 +77,61 @@ describe('buyQuoteCalculator', () => {
                     0,
                     0,
                     false,
+                );
+            };
+            testHelpers.expectInsufficientLiquidityError(expect, errorFunction, new BigNumber(400));
+        });
+        it('should throw if not enough maker asset liquidity (partially filled order)', () => {
+            const firstOrderAndFillableAmount: OrdersAndFillableAmounts = {
+                orders: [firstOrder],
+                remainingFillableMakerAssetAmounts: [firstRemainingFillAmount],
+            };
+
+            const errorFunction = () => {
+                buyQuoteCalculator.calculate(
+                    firstOrderAndFillableAmount,
+                    smallFeeOrderAndFillableAmount,
+                    new BigNumber(201),
+                    0,
+                    0,
+                    false,
+                );
+            };
+            testHelpers.expectInsufficientLiquidityError(expect, errorFunction, new BigNumber(200));
+        });
+        it('should throw if not enough maker asset liquidity (completely fillable order)', () => {
+            const completelyFillableOrder = orderFactory.createSignedOrderFromPartial({
+                makerAssetAmount: new BigNumber(123),
+                takerAssetAmount: new BigNumber(100),
+                takerFee: new BigNumber(200),
+            });
+            const completelyFillableOrdersAndFillableAmount: OrdersAndFillableAmounts = {
+                orders: [completelyFillableOrder],
+                remainingFillableMakerAssetAmounts: [completelyFillableOrder.makerAssetAmount],
+            };
+            const errorFunction = () => {
+                buyQuoteCalculator.calculate(
+                    completelyFillableOrdersAndFillableAmount,
+                    smallFeeOrderAndFillableAmount,
+                    new BigNumber(124),
+                    0,
+                    0,
+                    false,
+                );
+            };
+            testHelpers.expectInsufficientLiquidityError(expect, errorFunction, new BigNumber(123));
+        });
+        it('should not throw if order is fillable', () => {
+            expect(() =>
+                buyQuoteCalculator.calculate(
+                    ordersAndFillableAmounts,
+                    allFeeOrdersAndFillableAmounts,
+                    new BigNumber(300),
+                    0,
+                    0,
+                    false,
                 ),
-            ).to.throw(AssetBuyerError.InsufficientAssetLiquidity);
+            ).to.not.throw();
         });
         it('should throw if not enough ZRX liquidity', () => {
             // we request 300 makerAsset units but the ZRX order is only enough to fill the first order, which only has 200 makerAssetUnits available
diff --git a/packages/asset-buyer/test/utils/test_helpers.ts b/packages/asset-buyer/test/utils/test_helpers.ts
new file mode 100644
index 000000000..fd1313ac8
--- /dev/null
+++ b/packages/asset-buyer/test/utils/test_helpers.ts
@@ -0,0 +1,22 @@
+import { BigNumber } from '@0x/utils';
+
+import { InsufficientAssetLiquidityError } from '../../src/types';
+
+export const testHelpers = {
+    expectInsufficientLiquidityError: (
+        expect: Chai.ExpectStatic,
+        functionWhichTriggersError: () => void,
+        expectedNumAvailable: BigNumber,
+    ): void => {
+        let errorThrown = false;
+        try {
+            functionWhichTriggersError();
+        } catch (e) {
+            errorThrown = true;
+            expect(e).to.be.instanceOf(InsufficientAssetLiquidityError);
+            expect(e.numAssetsAvailable).to.be.bignumber.equal(expectedNumAvailable);
+        }
+
+        expect(errorThrown).to.be.true();
+    },
+};