[contract-addresses] Add ChainId type predicate (#756)

packages/contract-addresses/src/index.ts

@@ -1,20 +1,16 @@
 import addresses from '../addresses.json';
 
 export interface ContractAddresses {
-    zrxToken: string;
-    etherToken: string;
-    zeroExGovernor: string;
-    zrxVault: string;
-    staking: string;
-    stakingProxy: string;
     erc20BridgeProxy: string;
     erc20BridgeSampler: string;
-    exchangeProxyGovernor: string;
+    etherToken: string;
     exchangeProxy: string;
-    exchangeProxyTransformerDeployer: string;
     exchangeProxyFlashWallet: string;
+    exchangeProxyGovernor: string;
     exchangeProxyLiquidityProviderSandbox: string;
-    zrxTreasury: string;
+    exchangeProxyTransformerDeployer: string;
+    staking: string;
+    stakingProxy: string;
     transformers: {
         wethTransformer: string;
         payTakerTransformer: string;
@@ -22,21 +18,32 @@ export interface ContractAddresses {
         affiliateFeeTransformer: string;
         positiveSlippageFeeTransformer: string;
     };
+    zeroExGovernor: string;
+    zrxToken: string;
+    zrxTreasury: string;
+    zrxVault: string;
 }
 
 export enum ChainId {
     Mainnet = 1,
     Goerli = 5,
-    Ganache = 1337,
+    Optimism = 10,
     BSC = 56,
     Polygon = 137,
-    PolygonMumbai = 80001,
-    Avalanche = 43114,
     Fantom = 250,
-    Celo = 42220,
+    Ganache = 1337,
-    Optimism = 10,
-    Arbitrum = 42161,
     Base = 8453,
+    Arbitrum = 42161,
+    Avalanche = 43114,
+    Celo = 42220,
+    PolygonMumbai = 80001,
+}
+
+/**
+ * Narrow a JavaScript number to a Chain ID.
+ */
+export function isChainId(chainId: number): chainId is ChainId {
+    return Object.values(ChainId).includes(chainId);
 }
 
 /**

packages/contract-addresses/test/addresses_test.ts

@@ -2,7 +2,7 @@ import * as chai from 'chai';
 import { bufferToHex, rlphash } from 'ethereumjs-util';
 import 'mocha';
 
-import { ChainId, getContractAddressesForChainOrThrow } from '../src';
+import { ChainId, getContractAddressesForChainOrThrow, isChainId } from '../src';
 
 const expect = chai.expect;
 
@@ -68,3 +68,12 @@ describe('addresses.json sanity test', () => {
         });
     });
 });
+
+describe("isChainId", () => {
+    it("should return true for existing chain ids", () => {
+      expect(isChainId(1)).to.be.true;
+    });
+    it("should return false for non-existing chain ids", () => {
+      expect(isChainId(666)).to.be.false;
+    });
+});