Make the DeltaCalculator and the DeltaTransformer emit change events

Reviewed By: jeanlauliac

Differential Revision: D5765042

fbshipit-source-id: 5b45cc425b6afb4f8cead80ce967263936baa8c1

packages/metro-bundler/src/DeltaBundler/DeltaCalculator.js

@@ -12,6 +12,8 @@
 
 'use strict';
 
+const {EventEmitter} = require('events');
+
 import type Bundler, {BundlingOptions} from '../Bundler';
 import type {Options as JSTransformerOptions} from '../JSTransformer/worker';
 import type Resolver from '../Resolver';
@@ -31,7 +33,7 @@ export type DeltaResult = {
  * traverse the files that have been changed between calls and avoid having to
  * traverse the whole dependency tree for trivial small changes.
  */
-class DeltaCalculator {
+class DeltaCalculator extends EventEmitter {
   _bundler: Bundler;
   _resolver: Resolver;
   _options: BundleOptions;
@@ -46,6 +48,8 @@ class DeltaCalculator {
   _inverseDependencies: Map<string, Set<string>> = new Map();
 
   constructor(bundler: Bundler, resolver: Resolver, options: BundleOptions) {
+    super();
+
     this._bundler = bundler;
     this._options = options;
     this._resolver = resolver;
@@ -166,8 +170,11 @@ class DeltaCalculator {
   }): mixed => {
     this._modifiedFiles.add(filePath);
 
-    // TODO: Check if path is in current dependencies. If so, send an updated
+    // Notify users that there is a change in some of the bundle files. This
-    // bundle event.
+    // way the client can choose to refetch the bundle.
+    if (this._dependencies.has(filePath)) {
+      this.emit('change');
+    }
   };
 
   async _getDelta(modifiedFiles: Set<string>): Promise<DeltaResult> {

packages/metro-bundler/src/DeltaBundler/DeltaTransformer.js

@@ -14,6 +14,8 @@
 
 const DeltaCalculator = require('./DeltaCalculator');
 
+const {EventEmitter} = require('events');
+
 import type Bundler from '../Bundler';
 import type {Options as JSTransformerOptions} from '../JSTransformer/worker';
 import type Resolver from '../Resolver';
@@ -49,7 +51,7 @@ type Options = {|
  *     },
  *   }
  */
-class DeltaTransformer {
+class DeltaTransformer extends EventEmitter {
   _bundler: Bundler;
   _getPolyfills: ({platform: ?string}) => $ReadOnlyArray<string>;
   _polyfillModuleNames: $ReadOnlyArray<string>;
@@ -64,12 +66,16 @@ class DeltaTransformer {
     options: Options,
     bundleOptions: BundleOptions,
   ) {
+    super();
+
     this._bundler = bundler;
     this._deltaCalculator = deltaCalculator;
     this._getPolyfills = options.getPolyfills;
     this._polyfillModuleNames = options.polyfillModuleNames;
     this._getModuleId = this._bundler.getGetModuleIdFn();
     this._bundleOptions = bundleOptions;
+
+    this._deltaCalculator.on('change', this._onFileChange);
   }
 
   static async create(
@@ -95,6 +101,8 @@ class DeltaTransformer {
    * clean up memory and resources once this instance is not used anymore.
    */
   end() {
+    this._deltaCalculator.removeListener('change', this._onFileChange);
+
     return this._deltaCalculator.end();
   }
 
@@ -348,6 +356,10 @@ class DeltaTransformer {
 
     return await module.read(transformOptions);
   }
+
+  _onFileChange = () => {
+    this.emit('change');
+  };
 }
 
 module.exports = DeltaTransformer;

packages/metro-bundler/src/DeltaBundler/__tests__/DeltaCalculator-test.js

@@ -187,4 +187,26 @@ describe('DeltaCalculator', () => {
       deleted: new Set(['/bar', '/baz']),
     });
   });
+
+  it('should emit an event when there is a relevant file change', async done => {
+    await deltaCalculator.getDelta();
+
+    deltaCalculator.on('change', () => done());
+
+    fileWatcher.emit('change', {eventsQueue: [{filePath: '/foo'}]});
+  });
+
+  it('should not emit an event when there is a file changed outside the bundle', async () => {
+    jest.useFakeTimers();
+
+    const onChangeFile = jest.fn();
+    await deltaCalculator.getDelta();
+
+    deltaCalculator.on('change', onChangeFile);
+    fileWatcher.emit('change', {eventsQueue: [{filePath: '/another'}]});
+
+    jest.runAllTimers();
+
+    expect(onChangeFile.mock.calls.length).toBe(0);
+  });
 });

packages/metro-bundler/src/DeltaBundler/index.js

@@ -58,10 +58,19 @@ class DeltaBundler {
     this._options = options;
   }
 
-  /**
-   * Main method to build a Delta Bundler
-   */
   async build(options: Options): Promise<DeltaBundle> {
+    const {deltaTransformer, id} = await this.getDeltaTransformer(options);
+    const response = await deltaTransformer.getDelta();
+
+    return {
+      ...response,
+      id,
+    };
+  }
+
+  async getDeltaTransformer(
+    options: Options,
+  ): Promise<{deltaTransformer: DeltaTransformer, id: string}> {
     let bundleId = options.deltaBundleId;
 
     // If no bundle id is passed, generate a new one (which is going to be
@@ -83,10 +92,8 @@ class DeltaBundler {
       this._deltaTransformers.set(bundleId, deltaTransformer);
     }
 
-    const response = await deltaTransformer.getDelta();
-
     return {
-      ...response,
+      deltaTransformer,
       id: bundleId,
     };
   }