fix: absolute paths in moduleDirectories are invalid in Windows OS (#5398)

* fix #5396: preserve absolute paths in `moduleDirectories`

* refactor unit tests

* pretty

* refactor: use mock

* bug fix

* CHANGELOG

* adjust sample data in unit tests

* adjust sample data in unit tests

Author: warren-bank

CHANGELOG.md

@@ -24,6 +24,10 @@
   paths. ([#5403](https://github.com/facebook/jest/pull/5403))
 * `[jest-resolve]` Get builtin modules from node core.
   ([#5411](https://github.com/facebook/jest/pull/5411))
+* `[jest-resolve]` Detect and preserve absolute paths in `moduleDirectories`. Do
+  not generate additional (invalid) paths by prepending each ancestor of `cwd`
+  to the absolute path. Additionally, this fixes functionality in Windows OS.
+  ([#5398](https://github.com/facebook/jest/pull/5398))
 
 ## jest 22.1.4
 

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

@@ -190,3 +190,63 @@ describe('nodeModulesPaths', () => {
     expect(result[result.length - 1]).toBe('./customFolder');
   });
 });
+
+describe('Resolver.getModulePaths() -> nodeModulesPaths()', () => {
+  const _path = path;
+  let moduleMap;
+
+  beforeEach(() => {
+    jest.resetModules();
+
+    moduleMap = new ModuleMap({
+      duplicates: [],
+      map: [],
+      mocks: [],
+    });
+  });
+
+  afterAll(() => {
+    jest.resetModules();
+    jest.dontMock('path');
+  });
+
+  it('can resolve node modules relative to absolute paths in "moduleDirectories" on Windows platforms', () => {
+    jest.doMock('path', () => _path.win32);
+    const path = require('path');
+    const Resolver = require('../');
+
+    const cwd = 'D:\\temp\\project';
+    const src = 'C:\\path\\to\\node_modules';
+    const resolver = new Resolver(moduleMap, {
+      moduleDirectories: [src, 'node_modules'],
+    });
+    const dirs_expected = [
+      src,
+      cwd + '\\node_modules',
+      path.dirname(cwd) + '\\node_modules',
+      'D:\\node_modules',
+    ];
+    const dirs_actual = resolver.getModulePaths(cwd);
+    expect(dirs_actual).toEqual(expect.arrayContaining(dirs_expected));
+  });
+
+  it('can resolve node modules relative to absolute paths in "moduleDirectories" on Posix platforms', () => {
+    jest.doMock('path', () => _path.posix);
+    const path = require('path');
+    const Resolver = require('../');
+
+    const cwd = '/temp/project';
+    const src = '/path/to/node_modules';
+    const resolver = new Resolver(moduleMap, {
+      moduleDirectories: [src, 'node_modules'],
+    });
+    const dirs_expected = [
+      src,
+      cwd + '/node_modules',
+      path.dirname(cwd) + '/node_modules',
+      '/node_modules',
+    ];
+    const dirs_actual = resolver.getModulePaths(cwd);
+    expect(dirs_actual).toEqual(expect.arrayContaining(dirs_expected));
+  });
+});

packages/jest-resolve/src/node_modules_paths.js

@@ -44,13 +44,17 @@ export default function nodeModulesPaths(
     parsed = path.parse(parsed.dir);
   }
 
-  const dirs = paths.reduce((dirs, aPath) => {
-    return dirs.concat(
-      modules.map(moduleDir => {
-        return path.join(prefix, aPath, moduleDir);
-      }),
-    );
-  }, []);
+  const dirs = paths
+    .reduce((dirs, aPath) => {
+      return dirs.concat(
+        modules.map(moduleDir => {
+          return path.isAbsolute(moduleDir)
+            ? aPath === basedirAbs ? moduleDir : ''
+            : path.join(prefix, aPath, moduleDir);
+        }),
+      );
+    }, [])
+    .filter(dir => dir !== '');
 
   return options.paths ? dirs.concat(options.paths) : dirs;
 }