fix: Fix user override of customExportConditions in custom env subclasses

CHANGELOG.md

@@ -4,6 +4,8 @@
 
 ### Fixes
 
+- `[jest-environment-jsdom, jest-environment-node]` Fix assignment of `customExportConditions` via `testEnvironmentOptions` when custom env subclass defines a default value ([#13989](https://github.com/facebook/jest/pull/13989))
+
 ### Chore & Maintenance
 
 ### Performance

e2e/resolve-conditions/__tests__/custom-env-conditions-method-override.test.mjs

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * 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>/custom-env-conditions-method-override.js
+ */
+
+import {fn} from 'fake-dual-dep';
+
+test('returns correct message', () => {
+  expect(fn()).toBe('hello from deno');
+});

e2e/resolve-conditions/__tests__/custom-env-override-export-conditions.test.mjs

@@ -0,0 +1,15 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * 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>/custom-env.js
+ * @jest-environment-options {"customExportConditions": ["react-native"]}
+ */
+
+import {fn} from 'fake-dual-dep';
+
+test('returns correct message', () => {
+  expect(fn()).toBe('hello from react-native');
+});

e2e/resolve-conditions/__tests__/deno.test.mjs → e2e/resolve-conditions/__tests__/custom-env.test.mjs

@@ -4,7 +4,7 @@
  * 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>/deno-env.js
+ * @jest-environment <rootDir>/custom-env.js
  */
 
 import {fn} from 'fake-dual-dep';

e2e/resolve-conditions/deno-env.js → e2e/resolve-conditions/custom-env-conditions-method-override.js

@@ -9,7 +9,7 @@
 
 const NodeEnv = require('jest-environment-node').TestEnvironment;
 
-module.exports = class DenoEnvWithConditions extends NodeEnv {
+module.exports = class CustomEnvWithConditions extends NodeEnv {
   exportConditions() {
     return ['deno'];
   }

e2e/resolve-conditions/custom-env.js

@@ -0,0 +1,14 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * 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').TestEnvironment;
+
+module.exports = class CustomEnvWithConditions extends NodeEnv {
+  customExportConditions = ['deno'];
+};

packages/jest-environment-jsdom/src/index.ts

@@ -38,6 +38,7 @@ export default class JSDOMEnvironment implements JestEnvironment<number> {
   private errorEventListener: ((event: Event & {error: Error}) => void) | null;
   moduleMocker: ModuleMocker | null;
   customExportConditions = ['browser'];
+  private _configuredExportConditions?: Array<string>;
 
   constructor(config: JestEnvironmentConfig, context: EnvironmentContext) {
     const {projectConfig} = config;
@@ -119,7 +120,7 @@ export default class JSDOMEnvironment implements JestEnvironment<number> {
         Array.isArray(customExportConditions) &&
         customExportConditions.every(isString)
       ) {
-        this.customExportConditions = customExportConditions;
+        this._configuredExportConditions = customExportConditions;
       } else {
         throw new Error(
           'Custom export conditions specified but they are not an array of strings',
@@ -170,7 +171,7 @@ export default class JSDOMEnvironment implements JestEnvironment<number> {
   }
 
   exportConditions(): Array<string> {
-    return this.customExportConditions;
+    return this._configuredExportConditions ?? this.customExportConditions;
   }
 
   getVmContext(): Context | null {

packages/jest-environment-node/src/index.ts

@@ -64,6 +64,7 @@ export default class NodeEnvironment implements JestEnvironment<Timer> {
   global: Global.Global;
   moduleMocker: ModuleMocker | null;
   customExportConditions = ['node', 'node-addons'];
+  private _configuredExportConditions?: Array<string>;
 
   // while `context` is unused, it should always be passed
   constructor(config: JestEnvironmentConfig, _context: EnvironmentContext) {
@@ -147,7 +148,7 @@ export default class NodeEnvironment implements JestEnvironment<Timer> {
         Array.isArray(customExportConditions) &&
         customExportConditions.every(isString)
       ) {
-        this.customExportConditions = customExportConditions;
+        this._configuredExportConditions = customExportConditions;
       } else {
         throw new Error(
           'Custom export conditions specified but they are not an array of strings',
@@ -201,7 +202,7 @@ export default class NodeEnvironment implements JestEnvironment<Timer> {
   }
 
   exportConditions(): Array<string> {
-    return this.customExportConditions;
+    return this._configuredExportConditions ?? this.customExportConditions;
   }
 
   getVmContext(): Context | null {