jestjs · jeysal · Apr 29, 2022 · Apr 29, 2022
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ### Features
 
+- `[jest-environment-node, jest-environment-jsdom]` Allow specifying `customExportConditions` ([#12774](https://github.com/facebook/jest/pull/12774))
+
 ### Fixes
 
 ### Chore & Maintenance

diff --git a/docs/Configuration.md b/docs/Configuration.md
@@ -1362,7 +1362,11 @@ beforeAll(() => {
 
 Default: `{}`
 
-Test environment options that will be passed to the `testEnvironment`. The relevant options depend on the environment. For example, you can override options given to [`jsdom`](https://github.com/jsdom/jsdom) such as `{html: "<html lang="zh-cmn-Hant"></html>", url: 'https://jestjs.io/', userAgent: "Agent/007"}`.
+Test environment options that will be passed to the `testEnvironment`. The relevant options depend on the environment.
+
+For example, in `jest-environment-jsdom`, you can override options given to [`jsdom`](https://github.com/jsdom/jsdom) such as `{html: "<html lang="zh-cmn-Hant"></html>", url: 'https://jestjs.io/', userAgent: "Agent/007"}`.
+
+Both `jest-environment-jsdom` and `jest-environment-node` allow specifying `customExportConditions`, which allow you to control which versions of a library are loaded from `exports` in `package.json`. `jest-environment-jsdom` defaults to `['browser']`. `jest-environment-node` defaults to `['node', 'node-addons']`.
 
 These options can also be passed in a docblock, similar to `testEnvironment`. Note that it must be parseable by `JSON.parse`. Example:
 

diff --git a/docs/UpgradingToJest28.md b/docs/UpgradingToJest28.md
@@ -173,7 +173,7 @@ npm install --save-dev jest-jasmine2
 
 Jest now includes full support for [package `exports`](https://nodejs.org/api/packages.html#exports), which might mean that files you import are not resolved correctly.
 
-Additionally, Jest now supplies more conditions. `jest-environment-node` has `node` and `node-addons`, while `jest-environment-jsdom` has `browser`. As a result, you might e.g. get browser code which assumes ESM, when Jest provides `['require', 'browser']`. You can either report a bug to the library (or Jest, the implementation is new and might have bugs!), override the conditions Jest passes (via a custom test environment and overriding `exportConditions()`), using a custom resolver or `moduleMapper`. Lots of options, and you'll need to pick the correct one for your project.
+Additionally, Jest now supplies more conditions. `jest-environment-node` has `node` and `node-addons`, while `jest-environment-jsdom` has `browser`. As a result, you might e.g. get browser code which assumes ESM, when Jest provides `['require', 'browser']`. You can either report a bug to the library (or Jest, the implementation is new and might have bugs!), override the conditions Jest passes (by passing the `customExportConditions` option to the test environment), or use a custom resolver or `moduleMapper`. Lots of options, and you'll need to pick the correct one for your project.
 
 Known examples of packages that fails in Jest 28 are [`uuid`](https://npmjs.com/package/uuid) and [`nanoid`](https://npmjs.com/package/nanoid) when using the `jest-environment-jsdom` environment. For an analysis, and a potential workaround, see [this comment](https://github.com/microsoft/accessibility-insights-web/pull/5421#issuecomment-1109168149).
 

diff --git a/e2e/resolve-conditions/.gitignore b/e2e/resolve-conditions/.gitignore
@@ -0,0 +1 @@
+!node_modules
diff --git a/e2e/resolve-conditions/__tests__/jsdom-custom-export-conditions.test.mjs b/e2e/resolve-conditions/__tests__/jsdom-custom-export-conditions.test.mjs
@@ -0,0 +1,15 @@
+/**
+ * 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 jest-environment-jsdom
+ * @jest-environment-options {"customExportConditions": ["special"]}
+ */
+
+import {fn} from 'fake-dual-dep';
+
+test('returns correct message', () => {
+  expect(fn()).toEqual('hello from special');
+});
diff --git a/e2e/resolve-conditions/__tests__/node-custom-export-conditions.test.mjs b/e2e/resolve-conditions/__tests__/node-custom-export-conditions.test.mjs
@@ -0,0 +1,15 @@
+/**
+ * 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 jest-environment-node
+ * @jest-environment-options {"customExportConditions": ["special"]}
+ */
+
+import {fn} from 'fake-dual-dep';
+
+test('returns correct message', () => {
+  expect(fn()).toEqual('hello from special');
+});
diff --git a/e2e/resolve-conditions/node_modules/fake-dual-dep/package.json b/e2e/resolve-conditions/node_modules/fake-dual-dep/package.json
diff --git a/e2e/resolve-conditions/node_modules/fake-dual-dep/special.mjs b/e2e/resolve-conditions/node_modules/fake-dual-dep/special.mjs
diff --git a/packages/jest-environment-jsdom/src/index.ts b/packages/jest-environment-jsdom/src/index.ts
@@ -33,6 +33,7 @@ export default class JSDOMEnvironment implements JestEnvironment<number> {
   global: Win;
   private errorEventListener: ((event: Event & {error: Error}) => void) | null;
   moduleMocker: ModuleMocker | null;
+  customExportConditions = ['browser'];
 
   constructor(config: JestEnvironmentConfig, context: EnvironmentContext) {
     const {projectConfig} = config;
@@ -109,6 +110,20 @@ export default class JSDOMEnvironment implements JestEnvironment<number> {
       return originalRemoveListener.apply(this, args);
     };
 
+    if ('customExportConditions' in projectConfig.testEnvironmentOptions) {
+      const {customExportConditions} = projectConfig.testEnvironmentOptions;
+      if (
+        Array.isArray(customExportConditions) &&
+        customExportConditions.every(item => typeof item === 'string')
+      ) {
+        this.customExportConditions = customExportConditions;
+      } else {
+        throw new Error(
+          'Custom export conditions specified but they are not an array of strings',
+        );
+      }
+    }
+
     this.moduleMocker = new ModuleMocker(global as any);
 
     this.fakeTimers = new LegacyFakeTimers({
@@ -158,7 +173,7 @@ export default class JSDOMEnvironment implements JestEnvironment<number> {
   }
 
   exportConditions(): Array<string> {
-    return ['browser'];
+    return this.customExportConditions;
   }
 
   getVmContext(): Context | null {

diff --git a/packages/jest-environment-node/src/index.ts b/packages/jest-environment-node/src/index.ts
@@ -59,6 +59,7 @@ export default class NodeEnvironment implements JestEnvironment<Timer> {
   fakeTimersModern: ModernFakeTimers | null;
   global: Global.Global;
   moduleMocker: ModuleMocker | null;
+  customExportConditions = ['node', 'node-addons'];
 
   // while `context` is unused, it should always be passed
   constructor(config: JestEnvironmentConfig, _context: EnvironmentContext) {
@@ -111,6 +112,20 @@ export default class NodeEnvironment implements JestEnvironment<Timer> {
 
     installCommonGlobals(global, projectConfig.globals);
 
+    if ('customExportConditions' in projectConfig.testEnvironmentOptions) {
+      const {customExportConditions} = projectConfig.testEnvironmentOptions;
+      if (
+        Array.isArray(customExportConditions) &&
+        customExportConditions.every(item => typeof item === 'string')
+      ) {
+        this.customExportConditions = customExportConditions;
+      } else {
+        throw new Error(
+          'Custom export conditions specified but they are not an array of strings',
+        );
+      }
+    }
+
     this.moduleMocker = new ModuleMocker(global);
 
     const timerIdToRef = (id: number) => ({
@@ -157,7 +172,7 @@ export default class NodeEnvironment implements JestEnvironment<Timer> {
   }
 
   exportConditions(): Array<string> {
-    return ['node', 'node-addons'];
+    return this.customExportConditions;
   }
 
   getVmContext(): Context | null {