Provide require.main property (#5618)

* feat: provide `require.main` property

In tests `require.main` will be set to module from which the test are being executed.

* add integration test case

* use cross-platform regex in integration test

* update CHANGELOG.md

* remove unused imports

CHANGELOG.md

@@ -1,5 +1,10 @@
 ## master
 
+### Features
+
+* `[jest-runtime]` Provide `require.main` property set to module with test suite
+  ([#5618](https://github.com/facebook/jest/pull/5618))
+
 ## 22.4.0
 
 ### Fixes

integration-tests/__tests__/require_main.test.js

@@ -0,0 +1,18 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ *
+ * @flow
+ */
+
+'use strict';
+
+const runJest = require('../runJest');
+
+test('provides `require.main` set to test suite module', () => {
+  const {stderr, stdout} = runJest('require-main');
+  expect(stdout).not.toMatch('No tests found');
+  expect(stderr).toMatch(/PASS __tests__(\/|\\+)loader\.test\.js/);
+});

integration-tests/require-main/__tests__/loader.test.js

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ */
+'use strict';
+
+const loader = require('../loader');
+
+test('loader should load a module', () => {
+  expect(loader('../example.js')).toBeTruthy();
+});

integration-tests/require-main/example.js

@@ -0,0 +1,8 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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 = true;

integration-tests/require-main/loader.js

@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ */
+const path = require('path');
+
+module.exports = function load(moduleId) {
+  return require(path.join(path.dirname(require.main.filename), moduleId));
+};

integration-tests/require-main/package.json

@@ -0,0 +1,5 @@
+{
+  "jest": {
+    "testEnvironment": "node"
+  }
+}

packages/jest-runtime/src/__tests__/runtime_require_mock.test.js

@@ -173,5 +173,14 @@ describe('Runtime', () => {
         expect(exports.isManualMockModule).toBe(true);
       });
     });
+    it('provides `require.main` in mock', () =>
+      createRuntime(__filename).then(runtime => {
+        runtime._moduleRegistry[__filename] = module;
+        runtime.setMock(__filename, 'export_main', () => require.main, {
+          virtual: true,
+        });
+        const mainModule = runtime.requireMock(__filename, 'export_main');
+        expect(mainModule).toBe(module);
+      }));
   });
 });

packages/jest-runtime/src/__tests__/runtime_require_module.test.js

@@ -130,6 +130,17 @@ describe('Runtime requireModule', () => {
       });
     });
   });
+  it('provides `require.main` to modules', () =>
+    createRuntime(__filename).then(runtime => {
+      runtime._moduleRegistry[__filename] = module;
+      [
+        './test_root/modules_with_main/export_main.js',
+        './test_root/modules_with_main/re_export_main.js',
+      ].forEach(modulePath => {
+        const mainModule = runtime.requireModule(__filename, modulePath);
+        expect(mainModule).toBe(module);
+      });
+    }));
 
   it('throws on non-existent @providesModule modules', () =>
     createRuntime(__filename).then(runtime => {

packages/jest-runtime/src/__tests__/test_root/modules_with_main/export_main.js

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ */
+
+'use strict';
+
+module.exports = require.main;

packages/jest-runtime/src/__tests__/test_root/modules_with_main/re_export_main.js

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc. 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.
+ */
+
+'use strict';
+
+module.exports = require('./export_main');

packages/jest-runtime/src/index.js

@@ -519,7 +519,7 @@ class Runtime {
 
     localModule.paths = this._resolver.getModulePaths(dirname);
     Object.defineProperty(localModule, 'require', {
-      value: this._createRequireImplementation(filename, options),
+      value: this._createRequireImplementation(localModule, options),
     });
 
     const transformedFile = this._scriptTransformer.transform(
@@ -678,18 +678,38 @@ class Runtime {
   }
 
   _createRequireImplementation(
-    from: Path,
+    from: Module,
     options: ?InternalModuleOptions,
   ): LocalModuleRequire {
     const moduleRequire =
       options && options.isInternalModule
-        ? (moduleName: string) => this.requireInternalModule(from, moduleName)
-        : this.requireModuleOrMock.bind(this, from);
+        ? (moduleName: string) =>
+            this.requireInternalModule(from.filename, moduleName)
+        : this.requireModuleOrMock.bind(this, from.filename);
     moduleRequire.cache = Object.create(null);
     moduleRequire.extensions = Object.create(null);
-    moduleRequire.requireActual = this.requireModule.bind(this, from);
-    moduleRequire.requireMock = this.requireMock.bind(this, from);
-    moduleRequire.resolve = moduleName => this._resolveModule(from, moduleName);
+    moduleRequire.requireActual = this.requireModule.bind(this, from.filename);
+    moduleRequire.requireMock = this.requireMock.bind(this, from.filename);
+    moduleRequire.resolve = moduleName =>
+      this._resolveModule(from.filename, moduleName);
+    Object.defineProperty(
+      moduleRequire,
+      'main',
+      ({
+        enumerable: true,
+        get() {
+          let mainModule = from.parent;
+          while (
+            mainModule &&
+            mainModule.parent &&
+            mainModule.id !== mainModule.parent.id
+          ) {
+            mainModule = mainModule.parent;
+          }
+          return mainModule;
+        },
+      }: Object),
+    );
     return moduleRequire;
   }