Add option to define a custom resolver (jestjs#2998)

* Add option to define a custom resolver

* Add documentation for resolver config option

* Add test for when overriding default resolver

* Made it more clear in the docs what resolver is expected to return

docs/Configuration.md

@@ -240,6 +240,23 @@ Default: `false`
 
 If enabled, the module registry for every test file will be reset before running each individual test. This is useful to isolate modules for every test so that local module state doesn't conflict between tests. This can be done programmatically using [`jest.resetModules()`](#jest-resetmodules).
 
+### `resolver` [string]
+Default: `undefined`
+
+This option allows the use of a custom resolver. This resolver must be a node module that exports a function expecting a string as the first argument for the path to resolve and an object with the following structure as the second argument:
+
+```
+{
+  "basedir": string,
+  "browser": bool,
+  "extensions": [string],
+  "moduleDirectory": [string],
+  "paths": [string]
+}
+```
+
+The function should either return a path to the module that should be resolved or throw an error if the module can't be found.
+
 ### `rootDir` [string]
 Default: The root of the directory containing the `package.json` *or* the [`pwd`](http://en.wikipedia.org/wiki/Pwd) if no `package.json` is found
 

packages/jest-config/src/normalize.js

@@ -296,6 +296,7 @@ function normalize(config: InitialConfig, argv: Object = {}) {
         break;
       case 'setupTestFrameworkScriptFile':
       case 'testResultsProcessor':
+      case 'resolver':
         //$FlowFixMe
         value = resolve(config.rootDir, key, config[key]);
         break;

packages/jest-config/src/validConfig.js

@@ -60,6 +60,7 @@ module.exports = ({
   preset: 'react-native',
   resetMocks: false,
   resetModules: false,
+  resolver: '<rootDir>/resolver.js',
   rootDir: '/',
   roots: ['<rootDir>'],
   setupFiles: ['<rootDir>/setup.js'],

packages/jest-resolve/src/__mocks__/userResolver.js

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) 2014-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 = function userResolver(path, options) {
+  return 'module';
+};

packages/jest-resolve/src/__test__/resolve-test.js → packages/jest-resolve/src/__tests__/resolve-test.js

@@ -10,6 +10,7 @@
 
 'use strict';
 
+const path = require('path');
 const ModuleMap = require('jest-haste-map').ModuleMap;
 const Resolver = require('../');
 
@@ -37,3 +38,34 @@ describe('isCoreModule', () => {
     expect(isCore).toEqual(false);
   });
 });
+
+describe('findNodeModule', () => {
+  it('is possible to override the default resolver', () => {
+    const nodePaths = process.env.NODE_PATH
+      ? process.env.NODE_PATH.split(path.delimiter)
+      : null;
+
+    jest.mock('../__mocks__/userResolver');
+    const userResolver = require('../__mocks__/userResolver');
+    userResolver.mockImplementation(() => 'module');
+
+    const newPath = Resolver.findNodeModule('test', {
+      basedir: '/',
+      browser: true,
+      extensions: ['js'],
+      moduleDirectory: ['node_modules'],
+      paths: ['/something'],
+      resolver: require.resolve('../__mocks__/userResolver'),
+    });
+
+    expect(newPath).toBe('module');
+    expect(userResolver.mock.calls[0][0]).toBe('test');
+    expect(userResolver.mock.calls[0][1]).toEqual({
+      basedir: '/',
+      browser: true,
+      extensions: ['js'],
+      moduleDirectory: ['node_modules'],
+      paths: (nodePaths || []).concat(['/something']),
+    });
+  });
+});

packages/jest-resolve/src/defaultResolver.js

@@ -0,0 +1,40 @@
+/**
+ * Copyright (c) 2014-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.
+ *
+ * @flow
+ */
+
+'use strict';
+
+import type {Path} from 'types/Config';
+
+const resolve = require('resolve');
+const browserResolve = require('browser-resolve');
+
+type ResolverOptions = {|
+  basedir: Path,
+  browser?: boolean,
+  extensions?: Array<string>,
+  moduleDirectory?: Array<string>,
+  paths?: ?Array<Path>,
+|};
+
+function defaultResolver(path: Path, options: ResolverOptions) {
+  const resv = options.browser ? browserResolve : resolve;
+
+  return resv.sync(
+    path,
+    {
+      basedir: options.basedir,
+      extensions: options.extensions,
+      moduleDirectory: options.moduleDirectory,
+      paths: options.paths,
+    }
+  );
+}
+
+module.exports = defaultResolver;

packages/jest-resolve/src/index.js

@@ -15,8 +15,6 @@ import type {ModuleMap} from 'types/HasteMap';
 
 const nodeModulesPaths = require('resolve/lib/node-modules-paths');
 const path = require('path');
-const resolve = require('resolve');
-const browserResolve = require('browser-resolve');
 const isBuiltinModule = require('is-builtin-module');
 
 type ResolverConfig = {|
@@ -28,6 +26,7 @@ type ResolverConfig = {|
   moduleNameMapper: ?Array<ModuleNameMapperConfig>,
   modulePaths: Array<Path>,
   platforms?: Array<string>,
+  resolver: ?Path,
 |};
 
 type FindNodeModuleConfig = {|
@@ -36,6 +35,7 @@ type FindNodeModuleConfig = {|
   extensions?: Array<string>,
   moduleDirectory?: Array<string>,
   paths?: Array<Path>,
+  resolver?: ?Path,
 |};
 
 type ModuleNameMapperConfig = {|
@@ -73,6 +73,7 @@ class Resolver {
       moduleNameMapper: options.moduleNameMapper,
       modulePaths: options.modulePaths,
       platforms: options.platforms,
+      resolver: options.resolver,
     };
     this._moduleMap = moduleMap;
     this._moduleIDCache = Object.create(null);
@@ -81,13 +82,15 @@ class Resolver {
   }
 
   static findNodeModule(path: Path, options: FindNodeModuleConfig): ?Path {
+    /* $FlowFixMe */
+    const resolver = require(options.resolver || './defaultResolver.js');
     const paths = options.paths;
+
     try {
-      const resv = options.browser ? browserResolve : resolve;
-      return resv.sync(
-        path,
+      return resolver(path,
         {
           basedir: options.basedir,
+          browser: options.browser,
           extensions: options.extensions,
           moduleDirectory: options.moduleDirectory,
           paths: paths ? (nodePaths || []).concat(paths) : nodePaths,
@@ -145,6 +148,7 @@ class Resolver {
         extensions,
         moduleDirectory,
         paths,
+        resolver: this._options.resolver,
       });
 
       if (module) {

packages/jest-runtime/src/index.js

@@ -224,6 +224,7 @@ class Runtime {
       moduleNameMapper: getModuleNameMapper(config),
       modulePaths: config.modulePaths,
       platforms: config.haste.platforms,
+      resolver: config.resolver,
     });
   }
 

types/Config.js

@@ -91,6 +91,7 @@ export type Config = {|
   preset: ?string,
   resetMocks: boolean,
   resetModules: boolean,
+  resolver: ?Path,
   rootDir: Path,
   roots: Array<Path>,
   setupFiles: Array<Path>,
@@ -151,6 +152,7 @@ export type InitialConfig = {|
   preset?: ?string,
   resetMocks?: boolean,
   resetModules?: boolean,
+  resolver?: ?Path,
   rootDir: Path,
   roots?: Array<Path>,
   scriptPreprocessor?: string,