Add support for the "module" package.json field

dangerfile.js

@@ -94,8 +94,8 @@ const esModuleRegex = /^(import|export)\s(?!type(of\s|\s)(?!from)).*?$/gm;
 
 // Ensure the use of 'use strict' on all non-ES module files
 const noStrictFiles = newJsFiles.filter(filepath => {
-  const content = fs.readFileSync(filepath).toString();
-  return !esModuleRegex.test(content) && !includes(content, 'use strict');
+  const content = fs.readFileSync(filepath, 'utf8');
+  return !content.match(esModuleRegex) && !includes(content, 'use strict');
 });
 
 raiseIssueAboutPaths(fail, noStrictFiles, "'use strict'");

docs/Configuration.md

@@ -51,7 +51,7 @@ This option is disabled by default. If you are introducing Jest to a large organ
 ### `browser` [boolean]
 Default: `false`
 
-Respect Browserify's [`"browser"` field](https://github.com/substack/browserify-handbook#browser-field) in `package.json` when resolving modules. Some modules export different versions based on whether they are operating in Node or a browser.
+Respect the [`"browser"` field](https://github.com/substack/browserify-handbook#browser-field) in `package.json` when resolving modules. Some modules export different versions based on whether they are operating in Node or a browser.
 
 ### `bail` [boolean]
 Default: `false`
@@ -150,6 +150,13 @@ For example, the following would create a global `__DEV__` variable set to `true
 
 Note that, if you specify a global reference value (like an object or array) here, and some code mutates that value in the midst of running a test, that mutation will *not* be persisted across test runs for other test files.
 
+### `module` [boolean]
+Default: `false`
+
+Respect the [`"module"` field](https://github.com/nodejs/node-eps/blob/master/002-es6-modules.md) in `package.json`. Many libraries that contain ES modules ([import/export syntax](http://www.2ality.com/2014/09/es6-modules-final.html)) use this field as a pointer to their untranspiled (ES6+) source, in addition to the ubiquitous `"main"` field that points to precompiled ES5 javascript.
+
+_TL;DR: enable this if your project uses import/export syntax._
+
 ### `moduleFileExtensions` [array<string>]
 Default: `["js", "json", "jsx", "node"]`
 

examples/module-field/.babelrc

@@ -0,0 +1,3 @@
+{
+  "presets": ["es2015"]
+}

examples/module-field/__tests__/index.js

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc. All rights reserved.
+ * 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.
+ */
+import Contents from '../sample';
+
+describe('module field resolution', () => {
+  it('should return the correct file exports', () => {
+    expect(Contents).toBe('👏');
+  });
+});

examples/module-field/package.json

@@ -0,0 +1,13 @@
+{
+  "devDependencies": {
+    "babel-jest": "*",
+    "babel-preset-es2015": "*",
+    "jest": "*"
+  },
+  "jest": {
+    "module": true
+  },
+  "scripts": {
+    "test": "jest"
+  }
+}

examples/module-field/sample/correct.js

@@ -0,0 +1,7 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc. All rights reserved.
+ * 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.
+ */
+export default '👏';

examples/module-field/sample/package.json

@@ -0,0 +1,4 @@
+{
+    "main": "wrong.js",
+    "module": "correct.js"
+}

examples/module-field/sample/wrong.js

@@ -0,0 +1,9 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc. All rights reserved.
+ * 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.
+ */
+'use strict';
+
+module.exports = '😒';

packages/jest-config/src/__tests__/normalize-test.js

@@ -385,6 +385,17 @@ describe('testPathIgnorePatterns', () => {
   });
 });
 
+describe('module', () => {
+  it('falsy module is not overwritten', () => {
+    const config = normalize({
+      module: true,
+      rootDir: '/root/path/foo',
+    });
+
+    expect(config.module).toBe(true);
+  });
+});
+
 describe('modulePathIgnorePatterns', () => {
   it('does not normalize paths relative to rootDir', () => {
     // This is a list of patterns, so we can't assume any of them are

packages/jest-config/src/defaults.js

@@ -32,6 +32,7 @@ module.exports = ({
   haste: {
     providesModuleNodeModules: [],
   },
+  module: false,
   moduleDirectories: ['node_modules'],
   moduleFileExtensions: ['js', 'json', 'jsx', 'node'],
   moduleNameMapper: {},

packages/jest-config/src/normalize.js

@@ -344,6 +344,7 @@ function normalize(config: InitialConfig, argv: Object = {}) {
       case 'globals':
       case 'logHeapUsage':
       case 'logTransformErrors':
+      case 'module':
       case 'moduleDirectories':
       case 'moduleFileExtensions':
       case 'moduleLoader':

packages/jest-config/src/validConfig.js

@@ -45,6 +45,7 @@ module.exports = ({
   },
   logHeapUsage: true,
   logTransformErrors: true,
+  module: false,
   moduleDirectories: ['node_modules'],
   moduleFileExtensions: ['js', 'json', 'jsx', 'node'],
   moduleLoader: '<rootDir>',

packages/jest-resolve/src/index.js

@@ -24,6 +24,7 @@ type ResolverConfig = {|
   defaultPlatform: ?string,
   extensions: Array<string>,
   hasCoreModules: boolean,
+  module?: boolean,
   moduleDirectories: Array<string>,
   moduleNameMapper: ?Array<ModuleNameMapperConfig>,
   modulePaths: Array<Path>,
@@ -34,6 +35,7 @@ type FindNodeModuleConfig = {|
   basedir: Path,
   browser?: boolean,
   extensions?: Array<string>,
+  module?: boolean,
   moduleDirectory?: Array<string>,
   paths?: Array<Path>,
 |};
@@ -69,6 +71,7 @@ class Resolver {
       hasCoreModules: options.hasCoreModules === undefined
         ? true
         : options.hasCoreModules,
+      module: options.module,
       moduleDirectories: options.moduleDirectories || ['node_modules'],
       moduleNameMapper: options.moduleNameMapper,
       modulePaths: options.modulePaths,
@@ -83,13 +86,21 @@ class Resolver {
   static findNodeModule(path: Path, options: FindNodeModuleConfig): ?Path {
     const paths = options.paths;
     try {
-      const resv = options.browser ? browserResolve : resolve;
-      return resv.sync(
+      return (options.browser ? browserResolve : resolve).sync(
         path,
         {
           basedir: options.basedir,
           extensions: options.extensions,
           moduleDirectory: options.moduleDirectory,
+          packageFilter: options.module
+                          ? packageJson => {
+                            if (packageJson.module) {
+                              packageJson.main = packageJson.module;
+                            }
+
+                            return packageJson;
+                          }
+                          : x => x,
           paths: paths ? (nodePaths || []).concat(paths) : nodePaths,
         },
       );
@@ -143,6 +154,7 @@ class Resolver {
         basedir: dirname,
         browser: this._options.browser,
         extensions,
+        module: this._options.module,
         moduleDirectory,
         paths,
       });
@@ -320,6 +332,7 @@ class Resolver {
               basedir: dirname,
               browser: this._options.browser,
               extensions,
+              module: this._options.module,
               moduleDirectory,
               paths,
             },

packages/jest-runtime/src/index.js

@@ -218,6 +218,7 @@ class Runtime {
       defaultPlatform: config.haste.defaultPlatform,
       extensions: config.moduleFileExtensions.map(extension => '.' + extension),
       hasCoreModules: true,
+      module: config.module,
       moduleDirectories: config.moduleDirectories,
       moduleNameMapper: getModuleNameMapper(config),
       modulePaths: config.modulePaths,

types/Config.js

@@ -32,6 +32,7 @@ export type DefaultConfig = {|
   expand: boolean,
   globals: ConfigGlobals,
   haste: HasteConfig,
+  module: boolean,
   moduleDirectories: Array<string>,
   moduleFileExtensions: Array<string>,
   moduleNameMapper: {[key: string]: string},
@@ -76,6 +77,7 @@ export type Config = {|
   haste: HasteConfig,
   logHeapUsage: boolean,
   logTransformErrors: ?boolean,
+  module: boolean,
   moduleDirectories: Array<string>,
   moduleFileExtensions: Array<string>,
   moduleLoader: Path,
@@ -134,6 +136,7 @@ export type InitialConfig = {|
   haste?: HasteConfig,
   logHeapUsage?: boolean,
   logTransformErrors?: ?boolean,
+  module?: boolean,
   moduleDirectories?: Array<string>,
   moduleFileExtensions?: Array<string>,
   moduleLoader?: Path,