Migrate to ESM import/export syntax

.eslintrc.js

@@ -41,5 +41,23 @@ module.exports = {
         'import/no-extraneous-dependencies': 'off',
       },
     },
+    {
+      files: ['packages/**/*.js'],
+      rules: {
+        'import/no-commonjs': 'error',
+      },
+    },
+    {
+      files: [
+        'packages/metro/src/integration_tests/**/*.js',
+        'packages/metro-runtime/**/*.js',
+        '**/__tests__/**/*.js',
+        '**/__mocks__/**/*.js',
+        '**/__fixtures__/**/*.js',
+      ],
+      rules: {
+        'import/no-commonjs': 'off',
+      },
+    },
   ],
 };

packages/buck-worker-tool/src/CommandFailedError.js

@@ -9,19 +9,15 @@
  * @oncall react_native
  */
 
-'use strict';
-
 /**
  * Thrown to indicate the command failed and already output relevant error
  * information on the console.
  */
-class CommandFailedError extends Error {
+export default class CommandFailedError extends Error {
   constructor() {
     super(
       'The Buck worker-tool command failed. Diagnostics should have ' +
         'been printed on the standard error output.',
     );
   }
 }
-
-module.exports = CommandFailedError;

packages/buck-worker-tool/src/profiling.js

@@ -9,9 +9,7 @@
  * @oncall react_native
  */
 
-'use strict';
-
-const fs = require('fs');
+import fs from 'fs';
 
 let currentInspectorSession;
 let isProfiling = false;
@@ -20,13 +18,14 @@ function getInspectorSession() {
   if (currentInspectorSession) {
     return currentInspectorSession;
   }
+  // eslint-disable-next-line import/no-commonjs
   const inspector = require('inspector');
   currentInspectorSession = new inspector.Session();
   currentInspectorSession.connect();
   return currentInspectorSession;
 }
 
-async function startProfiling() {
+export async function startProfiling() {
   if (isProfiling) {
     return;
   }
@@ -37,7 +36,7 @@ async function startProfiling() {
   isProfiling = true;
 }
 
-async function stopProfilingAndWrite(workerName: ?string) {
+export async function stopProfilingAndWrite(workerName: ?string) {
   if (!isProfiling) {
     return;
   }
@@ -56,8 +55,3 @@ async function stopProfilingAndWrite(workerName: ?string) {
   );
   isProfiling = false;
 }
-
-module.exports = {
-  stopProfilingAndWrite,
-  startProfiling,
-};

packages/buck-worker-tool/src/third-party/JSONStream.js

@@ -5,6 +5,8 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+/* eslint-disable import/no-commonjs */
+
 /**
  * Copyright (c) 2011 Dominic Tarr.
  * Based on the JSONStream package: https://github.com/dominictarr/JSONStream

packages/buck-worker-tool/src/worker-tool.js

@@ -9,16 +9,14 @@
  * @oncall react_native
  */
 
-'use strict';
-
 import type {Writable} from 'stream';
 
-const {startProfiling, stopProfilingAndWrite} = require('./profiling');
-const JSONStream = require('./third-party/JSONStream');
-const {Console} = require('console');
-const duplexer = require('duplexer');
-const fs = require('fs');
-const invariant = require('invariant');
+import {startProfiling, stopProfilingAndWrite} from './profiling';
+import JSONStream from './third-party/JSONStream';
+import {Console} from 'console';
+import duplexer from 'duplexer';
+import fs from 'fs';
+import invariant from 'invariant';
 
 export type Command = (
   argv: Array<string>,
@@ -294,4 +292,4 @@ const success = (id: number) => ({
   exit_code: 0 as const,
 });
 
-module.exports = {buckWorker};
+export {buckWorker};

packages/metro-babel-register/src/babel-register.js

@@ -9,6 +9,8 @@
  * @oncall react_native
  */
 
+/* eslint-disable import/no-commonjs */
+
 'use strict';
 
 /*::

packages/metro-babel-register/src/plugins/babel-plugin-metro-replace-ts-require-assignment.js

@@ -8,6 +8,8 @@
  * @oncall react_native
  */
 
+/* eslint-disable import/no-commonjs */
+
 'use strict';
 
 // Replace `import thing = require('thing')` with `const thing = require('thing')` which allows us to keep CJS semantics

packages/metro-babel-transformer/src/index.js

@@ -9,12 +9,10 @@
  * @oncall react_native
  */
 
-'use strict';
-
 import type {BabelCoreOptions, BabelFileMetadata} from '@babel/core';
 
-const {parseSync, transformFromAstSync} = require('@babel/core');
-const nullthrows = require('nullthrows');
+import {parseSync, transformFromAstSync} from '@babel/core';
+import nullthrows from 'nullthrows';
 
 export type CustomTransformOptions = {
   [string]: mixed,
@@ -81,7 +79,12 @@ export type BabelTransformer = $ReadOnly<{
   getCacheKey?: () => string,
 }>;
 
-function transform({filename, options, plugins, src}: BabelTransformerArgs) {
+function transform({
+  filename,
+  options,
+  plugins,
+  src,
+}: BabelTransformerArgs): ReturnType<BabelTransformer['transform']> {
   const OLD_BABEL_ENV = process.env.BABEL_ENV;
   process.env.BABEL_ENV = options.dev
     ? 'development'
@@ -105,15 +108,16 @@ function transform({filename, options, plugins, src}: BabelTransformerArgs) {
       // You get this behavior by default when using Babel's `transform` method directly.
       cloneInputAst: false,
     };
-    const sourceAst: BabelNodeFile = options.hermesParser
-      ? // $FlowFixMe[incompatible-exact]
+    const sourceAst = options.hermesParser
+      ? // eslint-disable-next-line import/no-commonjs
         require('hermes-parser').parse(src, {
           babel: true,
           sourceType: babelConfig.sourceType,
         })
       : parseSync(src, babelConfig);
 
     const transformResult = transformFromAstSync<MetroBabelFileMetadata>(
+      // $FlowFixMe[incompatible-call] BabelFile vs BabelNodeFile
       sourceAst,
       src,
       babelConfig,
@@ -130,6 +134,9 @@ function transform({filename, options, plugins, src}: BabelTransformerArgs) {
   }
 }
 
-module.exports = ({
-  transform,
-}: BabelTransformer);
+// Type check exports
+/*::
+({transform}) as BabelTransformer;
+*/
+
+export {transform};

packages/metro-cache-key/src/index.js

@@ -9,18 +9,14 @@
  * @oncall react_native
  */
 
-'use strict';
+import crypto from 'crypto';
+import fs from 'fs';
 
-const crypto = require('crypto');
-const fs = require('fs');
-
-function getCacheKey(files: Array<string>): string {
+export function getCacheKey(files: Array<string>): string {
   return files
     .reduce(
       (hash, file) => hash.update('\0', 'utf8').update(fs.readFileSync(file)),
       crypto.createHash('md5'),
     )
     .digest('hex');
 }
-
-module.exports = {getCacheKey};

packages/metro-cache/src/Cache.js

@@ -9,11 +9,9 @@
  * @oncall react_native
  */
 
-'use strict';
-
 import type {CacheStore} from 'metro-cache';
 
-const {Logger} = require('metro-core');
+import {Logger} from 'metro-core';
 
 /**
  * Main cache class. Receives an array of cache instances, and sequentially
@@ -22,7 +20,7 @@ const {Logger} = require('metro-core');
  *
  * All get/set operations are logged via Metro's logger.
  */
-class Cache<T> {
+export default class Cache<T> {
   _stores: $ReadOnlyArray<CacheStore<T>>;
 
   _hits: WeakMap<Buffer, CacheStore<T>>;
@@ -138,5 +136,3 @@ class Cache<T> {
     return this._stores.length === 0;
   }
 }
-
-module.exports = Cache;

packages/metro-cache/src/__tests__/Cache-test.js

@@ -29,7 +29,7 @@ describe('Cache', () => {
 
   beforeEach(() => {
     Logger = require('metro-core').Logger;
-    Cache = require('../Cache');
+    Cache = require('../Cache').default;
 
     Logger.on('log', item => {
       log.push({

packages/metro-cache/src/__tests__/stableHash-test.js

@@ -8,9 +8,7 @@
  * @oncall react_native
  */
 
-'use strict';
-
-const stableHash = require('../stableHash');
+import stableHash from '../stableHash';
 
 describe('stableHash', () => {
   test('ensures that the hash implementation supports switched order properties', () => {

packages/metro-cache/src/index.js

@@ -9,23 +9,22 @@
  * @oncall react_native
  */
 
-'use strict';
-
-const Cache = require('./Cache');
-const stableHash = require('./stableHash');
-const AutoCleanFileStore = require('./stores/AutoCleanFileStore');
-const FileStore = require('./stores/FileStore');
-const HttpGetStore = require('./stores/HttpGetStore');
-const HttpStore = require('./stores/HttpStore');
+import Cache from './Cache';
+import stableHash from './stableHash';
+import AutoCleanFileStore from './stores/AutoCleanFileStore';
+import FileStore from './stores/FileStore';
+import HttpGetStore from './stores/HttpGetStore';
+import HttpStore from './stores/HttpStore';
 
 export type {Options as FileOptions} from './stores/FileStore';
 export type {Options as HttpOptions} from './stores/HttpStore';
 export type {CacheStore} from './types';
 
-module.exports.AutoCleanFileStore = AutoCleanFileStore;
-module.exports.Cache = Cache;
-module.exports.FileStore = FileStore;
-module.exports.HttpGetStore = HttpGetStore;
-module.exports.HttpStore = HttpStore;
-
-module.exports.stableHash = stableHash;
+export {
+  AutoCleanFileStore,
+  Cache,
+  FileStore,
+  HttpGetStore,
+  HttpStore,
+  stableHash,
+};

packages/metro-cache/src/stableHash.js

@@ -9,12 +9,10 @@
  * @oncall react_native
  */
 
-'use strict';
+import crypto from 'crypto';
+import canonicalize from 'metro-core/private/canonicalize';
 
-const crypto = require('crypto');
-const canonicalize = require('metro-core/private/canonicalize');
-
-function stableHash(value: mixed): Buffer {
+export default function stableHash(value: mixed): Buffer {
   return (
     crypto
       .createHash('md5')
@@ -25,5 +23,3 @@ function stableHash(value: mixed): Buffer {
       .digest('buffer')
   );
 }
-
-module.exports = stableHash;

packages/metro-cache/src/stores/AutoCleanFileStore.js

@@ -8,13 +8,11 @@
  * @flow
  */
 
-'use strict';
-
 import type {Options} from './FileStore';
 
-const FileStore = require('./FileStore');
-const fs = require('fs');
-const path = require('path');
+import FileStore from './FileStore';
+import fs from 'fs';
+import path from 'path';
 
 type CleanOptions = {
   ...Options,
@@ -59,7 +57,7 @@ function get<T>(property: ?T, defaultValue: T): T {
 /**
  * A FileStore that cleans itself up in a given interval
  */
-class AutoCleanFileStore<T> extends FileStore<T> {
+export default class AutoCleanFileStore<T> extends FileStore<T> {
   _intervalMs: number;
   _cleanupThresholdMs: number;
   _root: string;
@@ -103,5 +101,3 @@ class AutoCleanFileStore<T> extends FileStore<T> {
     this._scheduleCleanup();
   }
 }
-
-module.exports = AutoCleanFileStore;

packages/metro-cache/src/stores/FileStore.js

@@ -8,10 +8,8 @@
  * @flow
  */
 
-'use strict';
-
-const fs = require('fs');
-const path = require('path');
+import fs from 'fs';
+import path from 'path';
 
 const NULL_BYTE = 0x00;
 const NULL_BYTE_BUFFER = Buffer.from([NULL_BYTE]);
@@ -20,7 +18,7 @@ export type Options = {
   root: string,
 };
 
-class FileStore<T> {
+export default class FileStore<T> {
   _root: string;
 
   constructor(options: Options) {
@@ -90,5 +88,3 @@ class FileStore<T> {
     }
   }
 }
-
-module.exports = FileStore;