Fix NODE_PATH resolving for relative paths (jestjs#3616)

* Add failing integration test for relative NODE_PATH

It is failing because babel-jest traverses directories up searching for package.json, but the path is relative.

It is exposing the underlying issue that NODE_PATH can be relative, but the code assumes all paths are absolute by that point.

* Resolve NODE_PATH to absolute paths

This fixes the issue because the rest of the code assumes the path is already absolute.
We also resolve symlink if necessary.

* Fix unrelated test to match the code

This test started failing, but it was not testing NODE_PATH in the first place.

It just happened to include its output, and it's not empty on Travis.

The test used to have some copy pasta from how we calculate nodePaths, so I just synced that copy pasta.

* Nitty nit

* Exclude empty items from the array

They are empty if NODE_PATH is empty, and split() returns [''].

* fs.realpathSync() can return undefined

* Fix test to match last change

Author: gaearon

integration_tests/__tests__/node_path-test.js

@@ -0,0 +1,19 @@
+/**
+ * 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.
+ *
+ * @emails oncall+jsinfra
+ */
+'use strict';
+
+const runJest = require('../runJest');
+
+test('supports NODE_PATH', () => {
+  const result = runJest('node_path', [], {
+    nodePath: ['../node_path/src'],
+  });
+  expect(result.status).toBe(0);
+});

integration_tests/node_path/__tests__/node_path-test.js

@@ -0,0 +1,12 @@
+/**
+ * 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';
+
+test('can require by absolute path', () => {
+  expect(require('path/file.js')).toBe(42);
+});

integration_tests/node_path/package.json

@@ -0,0 +1,8 @@
+{
+  "jest": {
+    "testEnvironment": "node",
+    "transform": {
+      "^.+\\.jsx?$": "../../packages/babel-jest"
+    }
+  }
+}

integration_tests/node_path/src/path/file.js

@@ -0,0 +1,10 @@
+/**
+ * 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 = 42;

integration_tests/runJest.js

@@ -16,6 +16,7 @@ const {fileExists} = require('./utils');
 const JEST_PATH = path.resolve(__dirname, '../packages/jest-cli/bin/jest.js');
 
 type RunJestOptions = {
+  nodePath?: string,
   skipPkgJsonCheck?: boolean, // don't complain if can't find package.json
 };
 
@@ -45,7 +46,15 @@ function runJest(
     );
   }
 
-  const result = spawnSync(JEST_PATH, args || [], {cwd: dir});
+  const env = options.nodePath
+    ? Object.assign({}, process.env, {
+        NODE_PATH: options.nodePath,
+      })
+    : process.env;
+  const result = spawnSync(JEST_PATH, args || [], {
+    cwd: dir,
+    env,
+  });
 
   result.stdout = result.stdout && result.stdout.toString();
   result.stderr = result.stderr && result.stderr.toString();

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

@@ -10,6 +10,7 @@
 
 'use strict';
 
+const fs = require('fs');
 const path = require('path');
 const ModuleMap = require('jest-haste-map').ModuleMap;
 const Resolver = require('../');
@@ -41,8 +42,13 @@ describe('isCoreModule', () => {
 
 describe('findNodeModule', () => {
   it('is possible to override the default resolver', () => {
+    const cwd = process.cwd();
+    const resolvedCwd = fs.realpathSync(cwd) || cwd;
     const nodePaths = process.env.NODE_PATH
-      ? process.env.NODE_PATH.split(path.delimiter)
+      ? process.env.NODE_PATH
+          .split(path.delimiter)
+          .filter(Boolean)
+          .map(p => path.resolve(resolvedCwd, p))
       : null;
 
     jest.mock('../__mocks__/userResolver');

packages/jest-resolve/src/index.js

@@ -11,6 +11,7 @@
 import type {Path} from 'types/Config';
 import type {ModuleMap} from 'types/HasteMap';
 
+const fs = require('fs');
 const path = require('path');
 const nodeModulesPaths = require('resolve/lib/node-modules-paths');
 const isBuiltinModule = require('is-builtin-module');
@@ -49,8 +50,15 @@ export type ResolveModuleConfig = {|
 
 const NATIVE_PLATFORM = 'native';
 
+// We might be inside a symlink.
+const cwd = process.cwd();
+const resolvedCwd = fs.realpathSync(cwd) || cwd;
 const nodePaths = process.env.NODE_PATH
-  ? process.env.NODE_PATH.split(path.delimiter)
+  ? process.env.NODE_PATH
+      .split(path.delimiter)
+      .filter(Boolean)
+      // The resolver expects absolute paths.
+      .map(p => path.resolve(resolvedCwd, p))
   : null;
 
 class Resolver {