feat: pass conditions when resolving modules (#11859)

Author: SimenB

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ### Features
 
+- `[jest-resolver, jest-runtime]` Pass `conditions` to custom resolvers to enable them to implement support for package.json `exports` field ([#11859](https://github.com/facebook/jest/pull/11859))
+
 ### Fixes
 
 - `[@jest/reporters]` Use async transform if available to transform files with no coverage ([#11852](https://github.com/facebook/jest/pull/11852))

docs/Configuration.md

@@ -788,11 +788,13 @@ This option allows the use of a custom resolver. This resolver must be a node mo
 ```json
 {
   "basedir": string,
+  "conditions": [string],
   "defaultResolver": "function(request, options)",
   "extensions": [string],
   "moduleDirectory": [string],
   "paths": [string],
   "packageFilter": "function(pkg, pkgdir)",
+  "pathFilter": "function(pkg, path, relativePath)",
   "rootDir": [string]
 }
 ```
@@ -849,6 +851,8 @@ module.exports = (request, options) => {
 };
 ```
 
+While Jest does not support [package `exports`](https://nodejs.org/api/packages.html#packages_package_entry_points) (beyond `main`), Jest will provide `conditions` as an option when calling custom resolvers, which can be used to implement support for `exports` in userland. Jest will pass `['import', 'default']` when running a test in ESM mode, and `['require', 'default']` when running with CJS.
+
 ### `restoreMocks` \[boolean]
 
 Default: `false`

e2e/__tests__/__snapshots__/moduleNameMapper.test.ts.snap

@@ -41,7 +41,7 @@ FAIL __tests__/index.js
       12 | module.exports = () => 'test';
       13 |
 
-      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/resolver.js:566:17)
+      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/resolver.js:577:17)
       at Object.require (index.js:10:1)
 `;
 
@@ -70,6 +70,6 @@ FAIL __tests__/index.js
       12 | module.exports = () => 'test';
       13 |
 
-      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/resolver.js:566:17)
+      at createNoMappedModuleFoundError (../../packages/jest-resolve/build/resolver.js:577:17)
       at Object.require (index.js:10:1)
 `;

e2e/__tests__/__snapshots__/resolveNoFileExtensions.test.ts.snap

@@ -37,6 +37,6 @@ FAIL __tests__/test.js
         |                  ^
       9 |
 
-      at Resolver.resolveModule (../../packages/jest-resolve/build/resolver.js:318:11)
+      at Resolver.resolveModule (../../packages/jest-resolve/build/resolver.js:322:11)
       at Object.require (index.js:8:18)
 `;

e2e/__tests__/resolveConditions.test.ts

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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.
+ */
+
+import {resolve} from 'path';
+import {onNodeVersions} from '@jest/test-utils';
+import {runYarnInstall} from '../Utils';
+import runJest from '../runJest';
+
+const dir = resolve(__dirname, '..', 'resolve-conditions');
+
+beforeAll(() => {
+  runYarnInstall(dir);
+});
+
+// The versions where vm.Module exists and commonjs with "exports" is not broken
+onNodeVersions('^12.16.0 || >=13.7.0', () => {
+  test('resolves package exports correctly with custom resolver', () => {
+    // run multiple times to ensure there are no caching errors
+    for (let i = 0; i < 5; i++) {
+      const {exitCode} = runJest(dir, [], {
+        nodeOptions: '--experimental-vm-modules',
+      });
+      try {
+        expect(exitCode).toBe(0);
+      } catch (error) {
+        console.log(`Test failed on iteration ${i + 1}`);
+        throw error;
+      }
+    }
+  });
+});

e2e/resolve-conditions/__tests__/resolveCjs.test.cjs

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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 {fn} = require('../fake-dep');
+
+test('returns correct message', () => {
+  expect(fn()).toEqual('hello from CJS');
+});

e2e/resolve-conditions/__tests__/resolveEsm.test.mjs

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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.
+ */
+
+import {fn} from '../fake-dep';
+
+test('returns correct message', () => {
+  expect(fn()).toEqual('hello from ESM');
+});

e2e/resolve-conditions/fake-dep/module.cjs

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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 = {
+  fn: () => 'hello from CJS',
+};

e2e/resolve-conditions/fake-dep/module.mjs

@@ -0,0 +1,10 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. 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.
+ */
+
+export function fn() {
+  return 'hello from ESM';
+}

e2e/resolve-conditions/fake-dep/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "fake-dep",
+  "version": "1.0.0",
+  "exports": {
+    ".": {
+      "import": "./module.mjs",
+      "require": "./module.cjs"
+    }
+  }
+}