Merge pull request #1437 from 0xProject/feature/instant/tell-amount-available

[instant] Tell user how much of an asset is available

12 files changed, 273 insertions, 17 deletions

diff --git a/packages/asset-buyer/CHANGELOG.json b/packages/asset-buyer/CHANGELOG.json
index fcdb655fc..a7f8d3418 100644
--- a/packages/asset-buyer/CHANGELOG.json
+++ b/packages/asset-buyer/CHANGELOG.json
@@ -1,5 +1,14 @@
 [
     {
+        "version": "4.0.0",
+        "changes": [
+            {
+                "note": "Raise custom InsufficientAssetLiquidityError error with amountAvailableToFill attribute",
+                "pr": 1437
+            }
+        ]
+    },
+    {
         "timestamp": 1547040760,
         "version": "3.0.5",
         "changes": [
diff --git a/packages/asset-buyer/src/errors.ts b/packages/asset-buyer/src/errors.ts
new file mode 100644
index 000000000..ec5fe548c
--- /dev/null
+++ b/packages/asset-buyer/src/errors.ts
@@ -0,0 +1,22 @@
+import { BigNumber } from '@0x/utils';
+
+import { AssetBuyerError } from './types';
+
+/**
+ * Error class representing insufficient asset liquidity
+ */
+export class InsufficientAssetLiquidityError extends Error {
+    /**
+     * The amount availabe to fill (in base units) factoring in slippage.
+     */
+    public amountAvailableToFill: BigNumber;
+    /**
+     * @param amountAvailableToFill The amount availabe to fill (in base units) factoring in slippage
+     */
+    constructor(amountAvailableToFill: BigNumber) {
+        super(AssetBuyerError.InsufficientAssetLiquidity);
+        this.amountAvailableToFill = amountAvailableToFill;
+        // 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);
+    }
+}
diff --git a/packages/asset-buyer/src/index.ts b/packages/asset-buyer/src/index.ts
index 8418edb42..a42d7e272 100644
--- a/packages/asset-buyer/src/index.ts
+++ b/packages/asset-buyer/src/index.ts
@@ -9,6 +9,7 @@ export { SignedOrder } from '@0x/types';
 export { BigNumber } from '@0x/utils';
 
 export { AssetBuyer } from './asset_buyer';
+export { InsufficientAssetLiquidityError } from './errors';
 export { BasicOrderProvider } from './order_providers/basic_order_provider';
 export { StandardRelayerAPIOrderProvider } from './order_providers/standard_relayer_api_order_provider';
 export {
diff --git a/packages/asset-buyer/src/types.ts b/packages/asset-buyer/src/types.ts
index 3b573edca..d5d6be695 100644
--- a/packages/asset-buyer/src/types.ts
+++ b/packages/asset-buyer/src/types.ts
@@ -102,7 +102,7 @@ export interface AssetBuyerOpts {
 }
 
 /**
- * Possible errors thrown by an AssetBuyer instance or associated static methods.
+ * Possible error messages thrown by an AssetBuyer instance or associated static methods.
  */
 export enum AssetBuyerError {
     NoEtherTokenContractFound = 'NO_ETHER_TOKEN_CONTRACT_FOUND',
diff --git a/packages/asset-buyer/src/utils/buy_quote_calculator.ts b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
index b15b880c2..fcded6ab1 100644
--- a/packages/asset-buyer/src/utils/buy_quote_calculator.ts
+++ b/packages/asset-buyer/src/utils/buy_quote_calculator.ts
@@ -3,6 +3,7 @@ import { BigNumber } from '@0x/utils';
 import * as _ from 'lodash';
 
 import { constants } from '../constants';
+import { InsufficientAssetLiquidityError } from '../errors';
 import { AssetBuyerError, BuyQuote, BuyQuoteInfo, OrdersAndFillableAmounts } from '../types';
 
 import { orderUtils } from './order_utils';
@@ -33,7 +34,18 @@ 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);
+            // We needed the amount they requested to buy, plus the amount for slippage
+            const totalAmountRequested = assetBuyAmount.plus(slippageBufferAmount);
+            const amountAbleToFill = totalAmountRequested.minus(remainingFillAmount);
+            // multiplierNeededWithSlippage represents what we need to multiply the assetBuyAmount by
+            // in order to get the total amount needed considering slippage
+            // i.e. if slippagePercent was 0.2 (20%), multiplierNeededWithSlippage would be 1.2
+            const multiplierNeededWithSlippage = new BigNumber(1).plus(slippagePercentage);
+            // Given amountAvailableToFillConsideringSlippage * multiplierNeededWithSlippage = amountAbleToFill
+            // We divide amountUnableToFill by multiplierNeededWithSlippage to determine amountAvailableToFillConsideringSlippage
+            const amountAvailableToFillConsideringSlippage = amountAbleToFill.div(multiplierNeededWithSlippage).floor();
+
+            throw new InsufficientAssetLiquidityError(amountAvailableToFillConsideringSlippage);
         }
         // 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..fdc17ef25 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],
@@ -61,18 +67,137 @@ describe('buyQuoteCalculator', () => {
                 ],
             };
         });
-        it('should throw if not enough maker asset liquidity', () => {
-            // we have 400 makerAsset units available to fill but attempt to calculate a quote for 500 makerAsset units
+        describe('InsufficientLiquidityError', () => {
+            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
+                const errorFunction = () => {
+                    buyQuoteCalculator.calculate(
+                        ordersAndFillableAmounts,
+                        smallFeeOrderAndFillableAmount,
+                        new BigNumber(500),
+                        0,
+                        0,
+                        false,
+                    );
+                };
+                testHelpers.expectInsufficientLiquidityError(expect, errorFunction, new BigNumber(400));
+            });
+            it('should throw if not enough maker asset liquidity (multiple orders with 20% slippage)', () => {
+                // we have 400 makerAsset units available to fill but attempt to calculate a quote for 500 makerAsset units
+                const errorFunction = () => {
+                    buyQuoteCalculator.calculate(
+                        ordersAndFillableAmounts,
+                        smallFeeOrderAndFillableAmount,
+                        new BigNumber(500),
+                        0,
+                        0.2,
+                        false,
+                    );
+                };
+                testHelpers.expectInsufficientLiquidityError(expect, errorFunction, new BigNumber(333));
+            });
+            it('should throw if not enough maker asset liquidity (multiple orders with 5% slippage)', () => {
+                // we have 400 makerAsset units available to fill but attempt to calculate a quote for 500 makerAsset units
+                const errorFunction = () => {
+                    buyQuoteCalculator.calculate(
+                        ordersAndFillableAmounts,
+                        smallFeeOrderAndFillableAmount,
+                        new BigNumber(600),
+                        0,
+                        0.05,
+                        false,
+                    );
+                };
+                testHelpers.expectInsufficientLiquidityError(expect, errorFunction, new BigNumber(380));
+            });
+            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 throw with 1 amount available if no slippage', () => {
+                const smallOrder = orderFactory.createSignedOrderFromPartial({
+                    makerAssetAmount: new BigNumber(1),
+                    takerAssetAmount: new BigNumber(1),
+                    takerFee: new BigNumber(0),
+                });
+                const errorFunction = () => {
+                    buyQuoteCalculator.calculate(
+                        { orders: [smallOrder], remainingFillableMakerAssetAmounts: [smallOrder.makerAssetAmount] },
+                        smallFeeOrderAndFillableAmount,
+                        new BigNumber(600),
+                        0,
+                        0,
+                        false,
+                    );
+                };
+                testHelpers.expectInsufficientLiquidityError(expect, errorFunction, new BigNumber(1));
+            });
+            it('should throw without amount available to fill if amount rounds to 0', () => {
+                const smallOrder = orderFactory.createSignedOrderFromPartial({
+                    makerAssetAmount: new BigNumber(1),
+                    takerAssetAmount: new BigNumber(1),
+                    takerFee: new BigNumber(0),
+                });
+                const errorFunction = () => {
+                    buyQuoteCalculator.calculate(
+                        { orders: [smallOrder], remainingFillableMakerAssetAmounts: [smallOrder.makerAssetAmount] },
+                        smallFeeOrderAndFillableAmount,
+                        new BigNumber(600),
+                        0,
+                        0.2,
+                        false,
+                    );
+                };
+                testHelpers.expectInsufficientLiquidityError(expect, errorFunction, undefined);
+            });
+        });
+        it('should not throw if order is fillable', () => {
             expect(() =>
                 buyQuoteCalculator.calculate(
                     ordersAndFillableAmounts,
-                    smallFeeOrderAndFillableAmount,
-                    new BigNumber(500),
+                    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..9c7c244af
--- /dev/null
+++ b/packages/asset-buyer/test/utils/test_helpers.ts
@@ -0,0 +1,26 @@
+import { BigNumber } from '@0x/utils';
+
+import { InsufficientAssetLiquidityError } from '../../src/errors';
+
+export const testHelpers = {
+    expectInsufficientLiquidityError: (
+        expect: Chai.ExpectStatic,
+        functionWhichTriggersError: () => void,
+        expectedAmountAvailableToFill?: BigNumber,
+    ): void => {
+        let wasErrorThrown = false;
+        try {
+            functionWhichTriggersError();
+        } catch (e) {
+            wasErrorThrown = true;
+            expect(e).to.be.instanceOf(InsufficientAssetLiquidityError);
+            if (expectedAmountAvailableToFill) {
+                expect(e.amountAvailableToFill).to.be.bignumber.equal(expectedAmountAvailableToFill);
+            } else {
+                expect(e.amountAvailableToFill).to.be.undefined();
+            }
+        }
+
+        expect(wasErrorThrown).to.be.true();
+    },
+};
diff --git a/packages/instant/src/constants.ts b/packages/instant/src/constants.ts
index 22f0cb6a4..67558c84a 100644
--- a/packages/instant/src/constants.ts
+++ b/packages/instant/src/constants.ts
@@ -16,6 +16,7 @@ export const ONE_SECOND_MS = 1000;
 export const ONE_MINUTE_MS = ONE_SECOND_MS * 60;
 export const GIT_SHA = process.env.GIT_SHA;
 export const NODE_ENV = process.env.NODE_ENV;
+export const SLIPPAGE_PERCENTAGE = 0.2;
 export const NPM_PACKAGE_VERSION = process.env.NPM_PACKAGE_VERSION;
 export const DEFAULT_UNKOWN_ASSET_NAME = '???';
 export const ACCOUNT_UPDATE_INTERVAL_TIME_MS = ONE_SECOND_MS * 5;
diff --git a/packages/instant/src/util/asset.ts b/packages/instant/src/util/asset.ts
index faaeb7c22..b009a327f 100644
--- a/packages/instant/src/util/asset.ts
+++ b/packages/instant/src/util/asset.ts
@@ -1,8 +1,10 @@
-import { AssetBuyerError } from '@0x/asset-buyer';
+import { AssetBuyerError, InsufficientAssetLiquidityError } from '@0x/asset-buyer';
 import { AssetProxyId, ObjectMap } from '@0x/types';
+import { BigNumber } from '@0x/utils';
+import { Web3Wrapper } from '@0x/web3-wrapper';
 import * as _ from 'lodash';
 
-import { DEFAULT_UNKOWN_ASSET_NAME } from '../constants';
+import { BIG_NUMBER_ZERO, DEFAULT_UNKOWN_ASSET_NAME } from '../constants';
 import { assetDataNetworkMapping } from '../data/asset_data_network_mapping';
 import { Asset, AssetMetaData, ERC20Asset, Network, ZeroExInstantError } from '../types';
 
@@ -111,6 +113,21 @@ export const assetUtils = {
     assetBuyerErrorMessage: (asset: ERC20Asset, error: Error): string | undefined => {
         if (error.message === AssetBuyerError.InsufficientAssetLiquidity) {
             const assetName = assetUtils.bestNameForAsset(asset, 'of this asset');
+            if (
+                error instanceof InsufficientAssetLiquidityError &&
+                error.amountAvailableToFill.greaterThan(BIG_NUMBER_ZERO)
+            ) {
+                const unitAmountAvailableToFill = Web3Wrapper.toUnitAmount(
+                    error.amountAvailableToFill,
+                    asset.metaData.decimals,
+                );
+                const roundedUnitAmountAvailableToFill = unitAmountAvailableToFill.round(2, BigNumber.ROUND_DOWN);
+
+                if (roundedUnitAmountAvailableToFill.greaterThan(BIG_NUMBER_ZERO)) {
+                    return `There are only ${roundedUnitAmountAvailableToFill} ${assetName} available to buy`;
+                }
+            }
+
             return `Not enough ${assetName} available`;
         } else if (error.message === AssetBuyerError.InsufficientZrxLiquidity) {
             return 'Not enough ZRX available';
diff --git a/packages/instant/src/util/buy_quote_updater.ts b/packages/instant/src/util/buy_quote_updater.ts
index 6191c92e3..37974e71c 100644
--- a/packages/instant/src/util/buy_quote_updater.ts
+++ b/packages/instant/src/util/buy_quote_updater.ts
@@ -5,6 +5,7 @@ import * as _ from 'lodash';
 import { Dispatch } from 'redux';
 import { oc } from 'ts-optchain';
 
+import { SLIPPAGE_PERCENTAGE } from '../constants';
 import { Action, actions } from '../redux/actions';
 import { AffiliateInfo, ERC20Asset, QuoteFetchOrigin } from '../types';
 import { analytics } from '../util/analytics';
@@ -33,8 +34,12 @@ export const buyQuoteUpdater = {
         }
         const feePercentage = oc(options.affiliateInfo).feePercentage();
         let newBuyQuote: BuyQuote | undefined;
+        const slippagePercentage = SLIPPAGE_PERCENTAGE;
         try {
-            newBuyQuote = await assetBuyer.getBuyQuoteAsync(asset.assetData, baseUnitValue, { feePercentage });
+            newBuyQuote = await assetBuyer.getBuyQuoteAsync(asset.assetData, baseUnitValue, {
+                feePercentage,
+                slippagePercentage,
+            });
         } catch (error) {
             const errorMessage = assetUtils.assetBuyerErrorMessage(asset, error);
 
diff --git a/packages/instant/test/util/asset.test.ts b/packages/instant/test/util/asset.test.ts
index fc4e4e2e4..402a556d5 100644
--- a/packages/instant/test/util/asset.test.ts
+++ b/packages/instant/test/util/asset.test.ts
@@ -1,5 +1,6 @@
-import { AssetBuyerError } from '@0x/asset-buyer';
+import { AssetBuyerError, BigNumber, InsufficientAssetLiquidityError } from '@0x/asset-buyer';
 import { AssetProxyId, ObjectMap } from '@0x/types';
+import { Web3Wrapper } from '@0x/web3-wrapper';
 
 import { Asset, AssetMetaData, ERC20Asset, ERC20AssetMetaData, Network, ZeroExInstantError } from '../../src/types';
 import { assetUtils } from '../../src/util/asset';
@@ -19,6 +20,16 @@ const ZRX_ASSET: ERC20Asset = {
 const META_DATA_MAP: ObjectMap<AssetMetaData> = {
     [ZRX_ASSET_DATA]: ZRX_META_DATA,
 };
+const WAX_ASSET: ERC20Asset = {
+    assetData: '0xf47261b000000000000000000000000039bb259f66e1c59d5abef88375979b4d20d98022',
+    metaData: {
+        assetProxyId: AssetProxyId.ERC20,
+        decimals: 8,
+        primaryColor: '#EDB740',
+        symbol: 'wax',
+        name: 'WAX',
+    },
+};
 
 describe('assetDataUtil', () => {
     describe('bestNameForAsset', () => {
@@ -47,13 +58,39 @@ describe('assetDataUtil', () => {
         });
     });
     describe('assetBuyerErrorMessage', () => {
-        it('should return message for InsufficientAssetLiquidity', () => {
+        it('should return message for generic InsufficientAssetLiquidity error', () => {
             const insufficientAssetError = new Error(AssetBuyerError.InsufficientAssetLiquidity);
             expect(assetUtils.assetBuyerErrorMessage(ZRX_ASSET, insufficientAssetError)).toEqual(
                 'Not enough ZRX available',
             );
         });
-        it('should return message for InsufficientAssetLiquidity', () => {
+        describe('InsufficientAssetLiquidityError', () => {
+            it('should return custom message for token w/ 18 decimals', () => {
+                const amountAvailable = Web3Wrapper.toBaseUnitAmount(new BigNumber(20.059), 18);
+                expect(
+                    assetUtils.assetBuyerErrorMessage(ZRX_ASSET, new InsufficientAssetLiquidityError(amountAvailable)),
+                ).toEqual('There are only 20.05 ZRX available to buy');
+            });
+            it('should return custom message for token w/ 18 decimals and small amount available', () => {
+                const amountAvailable = Web3Wrapper.toBaseUnitAmount(new BigNumber(0.01), 18);
+                expect(
+                    assetUtils.assetBuyerErrorMessage(ZRX_ASSET, new InsufficientAssetLiquidityError(amountAvailable)),
+                ).toEqual('There are only 0.01 ZRX available to buy');
+            });
+            it('should return custom message for token w/ 8 decimals', () => {
+                const amountAvailable = Web3Wrapper.toBaseUnitAmount(new BigNumber(3), 8);
+                expect(
+                    assetUtils.assetBuyerErrorMessage(WAX_ASSET, new InsufficientAssetLiquidityError(amountAvailable)),
+                ).toEqual('There are only 3 WAX available to buy');
+            });
+            it('should return generic message when amount available rounds to zero', () => {
+                const amountAvailable = Web3Wrapper.toBaseUnitAmount(new BigNumber(0.002), 18);
+                expect(
+                    assetUtils.assetBuyerErrorMessage(ZRX_ASSET, new InsufficientAssetLiquidityError(amountAvailable)),
+                ).toEqual('Not enough ZRX available');
+            });
+        });
+        it('should return message for InsufficientZrxLiquidity', () => {
             const insufficientZrxError = new Error(AssetBuyerError.InsufficientZrxLiquidity);
             expect(assetUtils.assetBuyerErrorMessage(ZRX_ASSET, insufficientZrxError)).toEqual(
                 'Not enough ZRX available',
diff --git a/packages/monorepo-scripts/src/doc_gen_configs.ts b/packages/monorepo-scripts/src/doc_gen_configs.ts
index dfbe98028..7a4e6bb2c 100644
--- a/packages/monorepo-scripts/src/doc_gen_configs.ts
+++ b/packages/monorepo-scripts/src/doc_gen_configs.ts
@@ -9,6 +9,7 @@ export const docGenConfigs: DocGenConfigs = {
         Array: 'https://developer.mozilla.org/pt-PT/docs/Web/JavaScript/Reference/Global_Objects/Array',
         BigNumber: 'http://mikemcl.github.io/bignumber.js',
         Error: 'https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error',
+        ErrorConstructor: 'https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error',
         Buffer: 'https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/node/v9/index.d.ts#L262',
         'solc.StandardContractOutput':
             'https://solidity.readthedocs.io/en/v0.4.24/using-the-compiler.html#output-description',