fix(jest-resolve-dependencies): resolve mocks as dependencies

CHANGELOG.md

@@ -34,6 +34,7 @@
 - `[jest-snapshot]` Distinguish empty string from external snapshot not written ([#8880](https://github.com/facebook/jest/pull/8880))
 - `[jest-snapshot]` [**BREAKING**] Distinguish empty string from internal snapshot not written ([#8898](https://github.com/facebook/jest/pull/8898))
 - `[jest-transform]` Properly cache transformed files across tests ([#8890](https://github.com/facebook/jest/pull/8890))
+- `[jest-resolve-dependencies]` Resolve mocks as dependencies ([#8952](https://github.com/facebook/jest/pull/8952))
 
 ### Chore & Maintenance
 

packages/jest-resolve-dependencies/src/__tests__/__fixtures__/hasMocked/__mocks__/file.js

@@ -0,0 +1,9 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+module.exports = jest.fn();

packages/jest-resolve-dependencies/src/__tests__/__fixtures__/hasMocked/file.js

@@ -0,0 +1,9 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+module.exports = str => str;

packages/jest-resolve-dependencies/src/__tests__/__fixtures__/hasMocked/file.test.js

@@ -0,0 +1,9 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+require('./file');

packages/jest-resolve-dependencies/src/__tests__/dependency_resolver.test.ts

@@ -58,6 +58,17 @@ test('resolves dependencies for existing path', () => {
   ]);
 });
 
+test('includes the mocks of dependencies as dependencies', () => {
+  const resolved = dependencyResolver.resolve(
+    path.resolve(__dirname, '__fixtures__', 'hasMocked', 'file.test.js'),
+  );
+
+  expect(resolved).toEqual([
+    expect.stringContaining(path.join('hasMocked', 'file.js')),
+    expect.stringContaining(path.join('hasMocked', '__mocks__', 'file.js')),
+  ]);
+});
+
 test('resolves dependencies for scoped packages', () => {
   const resolved = dependencyResolver.resolve(
     path.resolve(__dirname, '__fixtures__', 'scoped.js'),

packages/jest-resolve-dependencies/src/index.ts

@@ -5,6 +5,7 @@
  * LICENSE file in the root directory of this source tree.
  */
 
+import * as path from 'path';
 import {Config} from '@jest/types';
 // eslint-disable-next-line import/no-extraneous-dependencies
 import {FS as HasteFS} from 'jest-haste-map';
@@ -51,19 +52,32 @@ class DependencyResolver {
       if (this._resolver.isCoreModule(dependency)) {
         return acc;
       }
+
       let resolvedDependency;
+      let resolvedMockDependency;
       try {
         resolvedDependency = this._resolver.resolveModule(
           file,
           dependency,
           options,
         );
       } catch (e) {
-        resolvedDependency = this._resolver.getMockModule(file, dependency);
+        resolvedMockDependency = this._resolver.getMockModule(file, dependency);
       }
 
       if (resolvedDependency) {
         acc.push(resolvedDependency);
+
+        // If we resolve a dependency, then look for a mock dependency
+        // of the same name in that dependency's directory.
+        resolvedMockDependency = this._resolver.getMockModule(
+          path.dirname(resolvedDependency),
+          path.basename(dependency),
+        );
+      }
+
+      if (resolvedMockDependency) {
+        acc.push(resolvedMockDependency);
       }
 
       return acc;