feat(Child processes): Support process message polution

packages/stryker/src/child-proxy/ChildProcessProxyWorker.ts

@@ -1,9 +1,12 @@
 import { serialize, deserialize } from '../utils/objectUtils';
 import { WorkerMessage, WorkerMessageKind, ParentMessage, autoStart } from './messageProtocol';
-import { setGlobalLogLevel } from 'log4js';
+import { setGlobalLogLevel, getLogger } from 'log4js';
 import PluginLoader from '../PluginLoader';
 
 export default class ChildProcessProxyWorker {
+
+  private log = getLogger(ChildProcessProxyWorker.name);
+
   realSubject: any;
 
   constructor() {
@@ -17,7 +20,8 @@ export default class ChildProcessProxyWorker {
   }
 
   private listenToParent() {
-    process.on('message', (serializedMessage: string) => {
+
+    const handler = (serializedMessage: string) => {
       const message = deserialize(serializedMessage) as WorkerMessage;
       switch (message.kind) {
         case WorkerMessageKind.Init:
@@ -26,6 +30,7 @@ export default class ChildProcessProxyWorker {
           const RealSubjectClass = require(message.requirePath).default;
           this.realSubject = new RealSubjectClass(...message.constructorArgs);
           this.send('init_done');
+          this.removeAnyAdditionalMessageListeners(handler);
           break;
         case WorkerMessageKind.Work:
           const result = this.realSubject[message.methodName](...message.args);
@@ -35,6 +40,24 @@ export default class ChildProcessProxyWorker {
               result
             });
           });
+          this.removeAnyAdditionalMessageListeners(handler);
+          break;
+      }
+    };
+    process.on('message', handler);
+  }
+
+  /**
+   * Remove any addition message listeners that might me eavesdropping.
+   * the @ngtools/webpack plugin listens to messages and throws an error whenever it could not handle a message
+   * @see https://github.com/angular/angular-cli/blob/f776d3cf7982b64734c57fe4407434e9f4ec09f7/packages/%40ngtools/webpack/src/type_checker.ts#L79
+   * @param exceptListener The listener that should remain
+   */
+  private removeAnyAdditionalMessageListeners(exceptListener: NodeJS.MessageListener) {
+    process.listeners('message').forEach(listener => {
+      if (listener !== exceptListener) {
+        this.log.debug('Removing an additional message listener, we don\'t want eavesdropping on our inter-process communication: %s', listener.toString());
+        process.removeListener('message', listener);
       }
     });
   }

packages/stryker/test/unit/child-proxy/ChildProcessWorkerSpec.ts

@@ -11,12 +11,19 @@ describe('ChildProcessProxyWorker', () => {
 
   let processOnStub: sinon.SinonStub;
   let processSendStub: sinon.SinonStub;
+  let processListenersStub: sinon.SinonStub;
   let setGlobalLogLevelStub: sinon.SinonStub;
+  let processRemoveListenerStub: sinon.SinonStub;
   let pluginLoaderMock: Mock<PluginLoader>;
-  let originalProcessSend: undefined | ((message: any, sendHandle?: any) => void);
+  let originalProcessSend: undefined | NodeJS.MessageListener;
+  let processes: NodeJS.MessageListener[];
 
   beforeEach(() => {
+    processes = [];
     processOnStub = sandbox.stub(process, 'on');
+    processListenersStub = sandbox.stub(process, 'listeners');
+    processListenersStub.returns(processes);
+    processRemoveListenerStub = sandbox.stub(process, 'removeListener');
     processSendStub = sandbox.stub();
     // process.send is normally undefined
     originalProcessSend = process.send;
@@ -38,36 +45,53 @@ describe('ChildProcessProxyWorker', () => {
   describe('after init message', () => {
 
     let sut: ChildProcessProxyWorker;
+    let initMessage: WorkerMessage;
 
     beforeEach(() => {
       sut = new ChildProcessProxyWorker();
-      const initMessage: WorkerMessage = {
+      initMessage = {
         kind: WorkerMessageKind.Init,
         logLevel: 'FooLevel',
         constructorArgs: ['FooBarName'],
         plugins: ['fooPlugin', 'barPlugin'],
         requirePath: require.resolve('./HelloClass')
       };
-      processOnStub.callArgWith(1, [serialize(initMessage)]);
     });
-
+    
     it('should create the correct real instance', () => {
+      processOnStub.callArgWith(1, [serialize(initMessage)]);
       expect(sut.realSubject).instanceOf(HelloClass);
       const actual = sut.realSubject as HelloClass;
       expect(actual.name).eq('FooBarName');
     });
-
+    
     it('should send "init_done"', async () => {
+      processOnStub.callArgWith(1, [serialize(initMessage)]);
       const expectedWorkerResponse: ParentMessage = 'init_done';
       await tick(); // make sure promise is resolved
       expect(processSendStub).calledWith(serialize(expectedWorkerResponse));
     });
+
+    it('should remove any additional listeners', async () => {
+      // Arrange
+      function noop() { }
+      processes.push(noop);
+
+      // Act
+      processOnStub.callArgWith(1, [serialize(initMessage)]);
+      await tick(); // make sure promise is resolved
 
+      // Assert
+      expect(processRemoveListenerStub).calledWith('message', noop);
+    });
+
     it('should set global log level', () => {
+      processOnStub.callArgWith(1, [serialize(initMessage)]);
       expect(setGlobalLogLevelStub).calledWith('FooLevel');
     });
-
+    
     it('should load plugins', () => {
+      processOnStub.callArgWith(1, [serialize(initMessage)]);
       expect(pluginLoader.default).calledWithNew;
       expect(pluginLoader.default).calledWith(['fooPlugin', 'barPlugin']);
       expect(pluginLoaderMock.load).called;
@@ -77,6 +101,7 @@ describe('ChildProcessProxyWorker', () => {
 
       async function actAndAssert(workerMessage: WorkMessage, expectedResult: WorkResult) {
         // Act
+        processOnStub.callArgWith(1, [serialize(initMessage)]);
         processOnStub.callArgWith(1, serialize(workerMessage));
         await tick();
         // Assert