Fix package main resolving issue

CHANGELOG.md

@@ -1,5 +1,10 @@
 ## master
 
+### Fixes
+
+* `[jest-resolve]` Add condition to avoid infinite loop when node module package main is ".".
+  ([#5344)](https://github.com/facebook/jest/pull/5344)
+
 ### Features
 * `[jest-cli]` `--changedSince`: allow selectively running tests for code
   changed since arbitrary revisions.

integration-tests/__tests__/resolve-node-module.test.js

@@ -0,0 +1,16 @@
+/**
+ * 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('resolve node module', () => {
+  const result = runJest('resolve-node-module');
+  expect(result.status).toBe(0);
+});

integration-tests/resolve-node-module/__mocks__/mock-jsx-module/index.jsx

@@ -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 = 'test jsx';

integration-tests/resolve-node-module/__mocks__/mock-jsx-module/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "mock-jsx-module",
+  "main": "."
+}

integration-tests/resolve-node-module/__mocks__/mock-module/index.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 = 'test';

integration-tests/resolve-node-module/__mocks__/mock-module/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "mock-module",
+  "main": "."
+}

integration-tests/resolve-node-module/__tests__/resolve-node-module.test.js

@@ -0,0 +1,21 @@
+/**
+ * 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';
+
+jest.mock('mock-module');
+jest.mock('mock-jsx-module');
+
+it('should resolve entry as index.js when package main is "."', () => {
+  const mockModule = require('mock-module');
+  expect(mockModule).toEqual('test');
+});
+
+it('should resolve entry as index with other configured module file extention when package main is "."', () => {
+  const mockJsxModule = require('mock-jsx-module');
+  expect(mockJsxModule).toEqual('test jsx');
+});

integration-tests/resolve-node-module/package.json

@@ -0,0 +1,6 @@
+{
+  "jest": {
+    "moduleFileExtensions": ["js", "json", "jsx"],
+    "testEnvironment": "node"
+  }
+}

packages/jest-resolve/src/default_resolver.js

@@ -129,7 +129,7 @@ function resolveSync(target: Path, options: ResolverOptions): Path {
       pkgmain = JSON.parse(body).main;
     } catch (e) {}
 
-    if (pkgmain) {
+    if (pkgmain && pkgmain !== '.') {
       const resolveTarget = path.resolve(name, pkgmain);
       const result = tryResolve(resolveTarget);
       if (result) {