RN buck: ModuleGraph: get rid of callbacks, async/await for the best

Reviewed By: davidaurelio

Differential Revision: D5842855

fbshipit-source-id: 71f9e799db4ad312213a20c1b1a93280e934d1e7

packages/metro-bundler/src/ModuleGraph/ModuleGraph.js

@@ -7,29 +7,25 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @flow
+ * @format
  */
 'use strict';
 
 const defaults = require('../defaults');
-const nullthrows = require('fbjs/lib/nullthrows');
-const parallel = require('async/parallel');
-const seq = require('async/seq');
+const denodeify: Denodeify = require('denodeify');
 const virtualModule = require('./module').virtual;
 
 import type {
   BuildResult,
   Callback,
   GraphFn,
-  GraphResult,
-  Module,
   PostProcessModules,
 } from './types.flow';
 
-type BuildFn = (
+export type BuildFn = (
   entryPoints: Iterable<string>,
   options: BuildOptions,
-  callback: Callback<BuildResult>,
-) => void;
+) => Promise<BuildResult>;
 
 type BuildOptions = {|
   getPolyfills: ({platform: ?string}) => $ReadOnlyArray<string>,
@@ -37,78 +33,50 @@ type BuildOptions = {|
   platform: string,
 |};
 
+type Denodeify = <A, B, C, T>(
+  (A, B, C, Callback<T>) => void,
+) => (A, B, C) => Promise<T>;
+
 exports.createBuildSetup = (
-  graph: GraphFn,
+  graphFn: GraphFn,
   postProcessModules: PostProcessModules,
   translateDefaultsPath: string => string = x => x,
-): BuildFn =>
-  (entryPoints, options, callback) => {
+): BuildFn => async (entryPoints, options) => {
   const {
-      getPolyfills = (({platform}) => []),
+    getPolyfills = ({platform}) => [],
     optimize = false,
     platform = defaults.platforms[0],
   } = options;
   const graphOptions = {optimize};
 
-    const graphWithOptions =
-      (entry, cb) => graph(entry, platform, graphOptions, cb);
-    const graphOnlyModules = seq(graphWithOptions, getModules);
+  const pgraph = denodeify(graphFn);
+  const graphWithOptions = entry => pgraph(entry, platform, graphOptions);
+  const graphOnlyModules = async m => (await graphWithOptions(m)).modules;
 
-    parallel({
-      graph: cb => graphWithOptions(entryPoints, (error, result) => {
-        if (error) {
-          cb(error);
-          return;
-        }
-        /* $FlowFixMe: not undefined if there is no error */
+  const [graph, moduleSystem, polyfills] = await Promise.all([
+    (async () => {
+      const result = await graphWithOptions(entryPoints);
       const {modules, entryModules} = result;
       const prModules = postProcessModules(modules, [...entryPoints]);
-        cb(null, {modules: prModules, entryModules});
-      }),
-      moduleSystem: cb => graphOnlyModules(
-        [translateDefaultsPath(defaults.moduleSystem)],
-        cb,
-      ),
-      polyfills: cb => graphOnlyModules(
-        getPolyfills({platform}).map(translateDefaultsPath),
-        cb,
-      ),
-    }, (
-      error: ?Error,
-      result?: {graph: GraphResult, moduleSystem: Array<Module>, polyfills: Array<Module>},
-    ) => {
-      if (error) {
-        callback(error);
-        return;
-      }
-
-      const {
-        graph: {modules, entryModules},
-        moduleSystem,
-        polyfills,
-      } = nullthrows(result);
+      return {modules: prModules, entryModules};
+    })(),
+    graphOnlyModules([translateDefaultsPath(defaults.moduleSystem)]),
+    graphOnlyModules(getPolyfills({platform}).map(translateDefaultsPath)),
+  ]);
 
+  const {entryModules} = graph;
   const preludeScript = prelude(optimize);
   const prependedScripts = [preludeScript, ...moduleSystem, ...polyfills];
-      callback(null, {
+  return {
     entryModules,
-        modules: prependedScripts.concat(modules),
+    modules: [...prependedScripts, ...graph.modules],
     prependedScripts,
-      });
-    });
   };
-
-const getModules = (x, cb) => cb(null, x.modules);
-
-function* concat<T>(...iterables: Array<Iterable<T>>): Iterable<T> {
-  for (const it of iterables) {
-    yield* it;
-  }
-}
+};
 
 function prelude(optimize) {
   return virtualModule(
     `var __DEV__=${String(!optimize)},` +
-    '__BUNDLE_START_TIME__=this.nativePerformanceNow?nativePerformanceNow():Date.now();'
+      '__BUNDLE_START_TIME__=this.nativePerformanceNow?nativePerformanceNow():Date.now();',
   );
 }

packages/metro-bundler/src/ModuleGraph/__tests__/ModuleGraph-test.js

@@ -5,10 +5,15 @@
  * This source code is licensed under the BSD-style license found in the
  * LICENSE file in the root directory of this source tree. An additional grant
  * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @emails oncall+javascript_foundation
+ * @format
  */
+
 'use strict';
 
 const ModuleGraph = require('../ModuleGraph');
+
 const defaults = require('../../defaults');
 
 const FILE_TYPE = 'module';
@@ -21,37 +26,34 @@ describe('build setup', () => {
   const noOptions = {};
   const noEntryPoints = [];
 
-  it('adds a prelude containing start time and `__DEV__` to the build', done => {
-    buildSetup(noEntryPoints, noOptions, (error, result) => {
-      expect(error).toEqual(null);
+  it('adds a prelude containing start time and `__DEV__` to the build', async () => {
+    const result = await buildSetup(noEntryPoints, noOptions);
 
     const [prelude] = result.modules;
     expect(prelude).toEqual({
       dependencies: [],
       file: {
-          code: 'var __DEV__=true,__BUNDLE_START_TIME__=' +
+        code:
+          'var __DEV__=true,__BUNDLE_START_TIME__=' +
           'this.nativePerformanceNow?nativePerformanceNow():Date.now();',
         map: null,
         path: '',
         type: 'script',
       },
     });
-      done();
-    });
   });
 
-  it('sets `__DEV__` to false in the prelude if optimization is enabled', done => {
-    buildSetup(noEntryPoints, {optimize: true}, (error, result) => {
+  it('sets `__DEV__` to false in the prelude if optimization is enabled', async () => {
+    const result = await buildSetup(noEntryPoints, {optimize: true});
     const [prelude] = result.modules;
-      expect(prelude.file.code)
-        .toEqual('var __DEV__=false,__BUNDLE_START_TIME__=' +
-            'this.nativePerformanceNow?nativePerformanceNow():Date.now();');
-      done();
-    });
+    expect(prelude.file.code).toEqual(
+      'var __DEV__=false,__BUNDLE_START_TIME__=' +
+        'this.nativePerformanceNow?nativePerformanceNow():Date.now();',
+    );
   });
 
-  it('places the module system implementation directly after the prelude', done => {
-    buildSetup(noEntryPoints, noOptions, (error, result) => {
+  it('places the module system implementation directly after the prelude', async () => {
+    const result = await buildSetup(noEntryPoints, noOptions);
     const [, moduleSystem] = result.modules;
     expect(moduleSystem).toEqual({
       dependencies: [],
@@ -61,26 +63,21 @@ describe('build setup', () => {
         type: FILE_TYPE,
       },
     });
-      done();
-    });
   });
 
-  it('places polyfills after the module system', done => {
-    buildSetup(noEntryPoints, polyfillOptions, (error, result) => {
+  it('places polyfills after the module system', async () => {
+    const result = await buildSetup(noEntryPoints, polyfillOptions);
     const list = polyfillOptions.getPolyfills();
     const polyfills = result.modules.slice(2, list.length + 2);
     expect(polyfills).toEqual(list.map(moduleFromPath));
-      done();
-    });
   });
 
-  it('places all entry points and dependencies at the end, post-processed', done => {
+  it('places all entry points and dependencies at the end, post-processed', async () => {
     const entryPoints = ['b', 'c', 'd'];
-    buildSetup(entryPoints, noOptions, (error, result) => {
-      expect(result.modules.slice(-4))
-        .toEqual(['a', 'b', 'c', 'd'].map(moduleFromPath));
-      done();
-    });
+    const result = await buildSetup(entryPoints, noOptions);
+    expect(result.modules.slice(-4)).toEqual(
+      ['a', 'b', 'c', 'd'].map(moduleFromPath),
+    );
   });
 });