Merge pull request #95 from 0xProject/cache_net_version

Cache `net_version` requests

4 files changed, 39 insertions, 1 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 16abcc0e9..413203e4c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@ v0.9.0 - TBD
 ------------------------
     * Move `zeroEx.exchange.getAvailableContractAddressesAsync` to `zeroEx.getAvailableExchangeContractAddressesAsync` (#94)
     * Move `zeroEx.exchange.getProxyAuthorizedContractAddressesAsync` to `zeroEx.getProxyAuthorizedExchangeContractAddressesAsync` (#94)
+    * Cache `net_version` requests and invalidate the cache on calls to `setProvider` (#95)
     * Rename `zeroEx.exchange.batchCancelOrderAsync` to `zeroEx.exchange.batchCancelOrdersAsync`
     * Rename `zeroEx.exchange.batchFillOrderAsync` to `zeroEx.exchange.batchFillOrdersAsync`
 
diff --git a/src/web3_wrapper.ts b/src/web3_wrapper.ts
index 630f0bef3..61bac45c9 100644
--- a/src/web3_wrapper.ts
+++ b/src/web3_wrapper.ts
@@ -5,11 +5,13 @@ import promisify = require('es6-promisify');
 
 export class Web3Wrapper {
     private web3: Web3;
+    private networkIdIfExists?: number;
     constructor(provider: Web3.Provider) {
         this.web3 = new Web3();
         this.web3.setProvider(provider);
     }
     public setProvider(provider: Web3.Provider) {
+        delete this.networkIdIfExists;
         this.web3.setProvider(provider);
     }
     public isAddress(address: string): boolean {
@@ -27,9 +29,14 @@ export class Web3Wrapper {
         return this.web3.currentProvider;
     }
     public async getNetworkIdIfExistsAsync(): Promise<number|undefined> {
+        if (!_.isUndefined(this.networkIdIfExists)) {
+          return this.networkIdIfExists;
+        }
+
         try {
             const networkId = await this.getNetworkAsync();
-            return Number(networkId);
+            this.networkIdIfExists = Number(networkId);
+            return this.networkIdIfExists;
         } catch (err) {
             return undefined;
         }
diff --git a/test/utils/constants.ts b/test/utils/constants.ts
index 9b150b5c1..b677d7361 100644
--- a/test/utils/constants.ts
+++ b/test/utils/constants.ts
@@ -2,5 +2,6 @@ export const constants = {
     NULL_ADDRESS: '0x0000000000000000000000000000000000000000',
     RPC_HOST: 'localhost',
     RPC_PORT: 8545,
+    TESTRPC_NETWORK_ID: 50,
     KOVAN_RPC_URL: 'https://kovan.0xproject.com',
 };
diff --git a/test/web3_wrapper_test.ts b/test/web3_wrapper_test.ts
new file mode 100644
index 000000000..d1c2e8e89
--- /dev/null
+++ b/test/web3_wrapper_test.ts
@@ -0,0 +1,29 @@
+import * as chai from 'chai';
+import {web3Factory} from './utils/web3_factory';
+import {ZeroEx} from '../src/';
+import {Web3Wrapper} from '../src/web3_wrapper';
+import {constants} from './utils/constants';
+
+chai.config.includeStack = true;
+const expect = chai.expect;
+
+describe('Web3Wrapper', () => {
+    const web3Provider = web3Factory.create().currentProvider;
+    describe('#getNetworkIdIfExistsAsync', () => {
+        it('caches network id requests', async () => {
+            const web3Wrapper = (new ZeroEx(web3Provider) as any)._web3Wrapper as Web3Wrapper;
+            expect((web3Wrapper as any).networkIdIfExists).to.be.undefined();
+            const networkIdIfExists = await web3Wrapper.getNetworkIdIfExistsAsync();
+            expect((web3Wrapper as any).networkIdIfExists).to.be.equal(constants.TESTRPC_NETWORK_ID);
+        });
+        it('invalidates network id cache on setProvider call', async () => {
+            const web3Wrapper = (new ZeroEx(web3Provider) as any)._web3Wrapper as Web3Wrapper;
+            expect((web3Wrapper as any).networkIdIfExists).to.be.undefined();
+            const networkIdIfExists = await web3Wrapper.getNetworkIdIfExistsAsync();
+            expect((web3Wrapper as any).networkIdIfExists).to.be.equal(constants.TESTRPC_NETWORK_ID);
+            const newProvider = web3Factory.create().currentProvider;
+            web3Wrapper.setProvider(newProvider);
+            expect((web3Wrapper as any).networkIdIfExists).to.be.undefined();
+        });
+    });
+});