feat: support conditions from test environments

Author: SimenB

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### 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))
+- `[jest-runtime]` Allow custom envs to specify `exportConditions` which is passed together with Jest's own conditions to custom resolvers ([#11863](https://github.com/facebook/jest/pull/11863))
 
 ### Fixes
 

docs/Configuration.md

@@ -851,7 +851,7 @@ 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.
+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. Additionally, custom test environments can specify an `exportConditions` method which returns an array of conditions that will be passed along with Jest's defaults.
 
 ### `restoreMocks` \[boolean]
 

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

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ *
+ * @jest-environment <rootDir>/browser-env.js
+ */
+
+import {fn} from '../fake-dual-dep';
+
+test('returns correct message', () => {
+  expect(fn()).toEqual('hello from browser');
+});

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

@@ -0,0 +1,14 @@
+/**
+ * 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.
+ *
+ * @jest-environment <rootDir>/node-env.js
+ */
+
+import {fn} from '../fake-dual-dep';
+
+test('returns correct message', () => {
+  expect(fn()).toEqual('hello from node');
+});

e2e/resolve-conditions/browser-env.js

@@ -0,0 +1,16 @@
+/**
+ * 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.
+ */
+
+'use strict';
+
+const BrowserEnv = require('jest-environment-jsdom');
+
+module.exports = class BrowserEnvWithConditions extends BrowserEnv {
+  exportConditions() {
+    return ['browser'];
+  }
+};

e2e/resolve-conditions/fake-dual-dep/browser.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 browser';
+}

e2e/resolve-conditions/fake-dual-dep/node.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 node';
+}

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

@@ -0,0 +1,10 @@
+{
+  "name": "fake-dual-dep",
+  "version": "1.0.0",
+  "exports": {
+    ".": {
+      "node": "./node.mjs",
+      "browser": "./browser.mjs"
+    }
+  }
+}

e2e/resolve-conditions/node-env.js

@@ -0,0 +1,16 @@
+/**
+ * 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.
+ */
+
+'use strict';
+
+const NodeEnv = require('jest-environment-node');
+
+module.exports = class NodeEnvWithConditions extends NodeEnv {
+  exportConditions() {
+    return ['node'];
+  }
+};

e2e/resolve-conditions/resolver.js

@@ -25,9 +25,11 @@ function createPathFilter(conditions) {
 
     return (
       resolveExports(pkg, path, {
+        // `resolve.exports adds `node` unless `browser` is `false`, so let's add this ugly thing
+        browser: conditions.includes('browser'),
         conditions,
         // `resolve.exports adds `import` unless `require` is `false`, so let's add this ugly thing
-        require: !conditions.includes('import'),
+        require: conditions.includes('require'),
       }) || relativePath
     );
   };