Throw when moduleNameMapper points to inexistent module

integration_tests/__tests__/__snapshots__/module_name_mapper.test.js.snap

@@ -0,0 +1,24 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`moduleNameMapper correct configuration 1`] = `
+" PASS  __tests__/index.js
+  ✓ moduleNameMapping correct configuration
+
+"
+`;
+
+exports[`moduleNameMapper wrong configuration 1`] = `
+" FAIL  __tests__/index.js
+  ● Test suite failed to run
+
+    Configuration error:
+
+    Unknown module in configuration option moduleNameMapper
+    Please check:
+
+    \\"moduleNameMapper\\": {
+      \\"/\\\\.(css|less)$/\\": \\"no-such-module\\"
+    }
+
+"
+`;

integration_tests/__tests__/auto_clear_mocks.test.js

@@ -4,19 +4,25 @@
  * 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+jsinfra
  */
+
 'use strict';
 
 const runJest = require('../runJest');
+const {extractSummary} = require('../utils');
 
-test('suite with auto-clear', () => {
-  const result = runJest('auto-clear-mocks/with-auto-clear');
-  expect(result.status).toBe(0);
+test('moduleNameMapper wrong configuration', () => {
+  const {stderr, status} = runJest('moduleNameMapper-wrong-config');
+  const {rest} = extractSummary(stderr);
+
+  expect(status).toBe(1);
+  expect(rest).toMatchSnapshot();
 });
 
-test('suite without auto-clear', () => {
-  const result = runJest('auto-clear-mocks/without-auto-clear');
-  expect(result.status).toBe(0);
+test('moduleNameMapper correct configuration', () => {
+  const {stderr, status} = runJest('moduleNameMapper-correct-config');
+  const {rest} = extractSummary(stderr);
+
+  expect(status).toBe(0);
+  expect(rest).toMatchSnapshot();
 });

integration_tests/__tests__/auto_reset_mocks.test.js

@@ -7,6 +7,7 @@
  *
  * @emails oncall+jsinfra
  */
+
 'use strict';
 
 const runJest = require('../runJest');

integration_tests/__tests__/module_name_mapper.test.js

@@ -0,0 +1,27 @@
+/**
+ * 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';
+
+const runJest = require('../runJest');
+const {extractSummary} = require('../utils');
+
+test('moduleNameMapper wrong configuration', () => {
+  const {stderr, status} = runJest('module_name_mapper_wrong_config');
+  const {rest} = extractSummary(stderr);
+
+  expect(status).toBe(1);
+  expect(rest).toMatchSnapshot();
+});
+
+test('moduleNameMapper correct configuration', () => {
+  const {stderr, status} = runJest('module_name_mapper_correct_config');
+  const {rest} = extractSummary(stderr);
+
+  expect(status).toBe(0);
+  expect(rest).toMatchSnapshot();
+});

integration_tests/auto-clear-mocks/with-auto-clear/index.js

@@ -5,7 +5,6 @@
  * 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
  */
 
 module.exports = () => {};

integration_tests/auto-clear-mocks/without-auto-clear/index.js

@@ -5,7 +5,6 @@
  * 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
  */
 
 module.exports = () => {};

integration_tests/module_name_mapper_correct_config/__mocks__/style_mock.js

@@ -0,0 +1,11 @@
+/**
+ * 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 = {};

integration_tests/module_name_mapper_correct_config/__tests__/index.js

@@ -0,0 +1,15 @@
+/**
+ * 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';
+
+const importedFn = require('../');
+
+test('moduleNameMapping correct configuration', () => {
+  expect(importedFn).toBeDefined();
+});

integration_tests/module_name_mapper_correct_config/index.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';
+
+require('./style.css');
+
+module.exports = () => 'test';

integration_tests/module_name_mapper_correct_config/package.json

@@ -0,0 +1,7 @@
+{
+  "jest": {
+    "moduleNameMapper": {
+      "\\.(css|less)$": "./__mocks__/style_mock.js"
+    }
+  }
+}

integration_tests/module_name_mapper_wrong_config/__tests__/index.js

@@ -0,0 +1,15 @@
+/**
+ * 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';
+
+const importedFn = require('../');
+
+test('moduleNameMapping wrong configuration', () => {
+  expect(importedFn).toBeDefined();
+});

integration_tests/module_name_mapper_wrong_config/index.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';
+
+require('./style.css');
+
+module.exports = () => 'test';

integration_tests/module_name_mapper_wrong_config/package.json

@@ -0,0 +1,7 @@
+{
+  "jest": {
+    "moduleNameMapper": {
+      "\\.(css|less)$": "no-such-module"
+    }
+  }
+}

packages/jest-resolve/package.json

@@ -9,6 +9,7 @@
   "main": "build/index.js",
   "dependencies": {
     "browser-resolve": "^1.11.2",
+    "chalk": "^1.1.3",
     "is-builtin-module": "^1.0.0",
     "resolve": "^1.3.2"
   },

packages/jest-resolve/src/index.js

@@ -16,6 +16,7 @@ import path from 'path';
 import nodeModulesPaths from 'resolve/lib/node-modules-paths';
 import isBuiltinModule from 'is-builtin-module';
 import defaultResolver from './default_resolver.js';
+import chalk from 'chalk';
 
 type ResolverConfig = {|
   browser?: boolean,
@@ -317,8 +318,8 @@ class Resolver {
     const paths = this._options.modulePaths;
     const extensions = this._options.extensions;
     const moduleDirectory = this._options.moduleDirectories;
-
     const moduleNameMapper = this._options.moduleNameMapper;
+
     if (moduleNameMapper) {
       for (const {moduleName: mappedModuleName, regex} of moduleNameMapper) {
         if (regex.test(moduleName)) {
@@ -331,16 +332,31 @@ class Resolver {
               (_, index) => matches[parseInt(index, 10)],
             );
           }
-          return (
+
+          const module =
             this.getModule(moduleName) ||
             Resolver.findNodeModule(moduleName, {
               basedir: dirname,
               browser: this._options.browser,
               extensions,
               moduleDirectory,
               paths,
-            })
-          );
+            });
+          if (!module) {
+            const error = new Error(
+              chalk.red(`${chalk.bold('Configuration error')}:
+
+Unknown module in configuration option ${chalk.bold('moduleNameMapper')}
+Please check:
+
+"moduleNameMapper": {
+  "${regex.toString()}": "${chalk.bold(moduleName)}"
+}`),
+            );
+            error.stack = '';
+            throw error;
+          }
+          return module;
         }
       }
     }