fix: adapt tests after Monaco 1.108 uplift

- Add ESM loader hooks in @theia/test-setup to handle .css imports
  from @theia/monaco-editor-core ESM bundles during mocha test runs
- Fix expose-loader to use module.exports instead of this for webpack
  compatibility with ESM modules, where this is undefined in arrow
  function wrappers
- Move top-level const { timeout } declarations inside describe()
  blocks to avoid duplicate identifier errors when files share scope
- Replace keyboard.type() with keyboard.insertText() in Playwright
  tests for Monaco EditContext API compatibility
- Add TheiaMonacoEditor.typeText() static helper that handles
  multi-line text (insertText for content, Enter for newlines)
- Update line-numbers selector to .margin-view-overlays .line-numbers
  to match Monaco 1.108 DOM
- Add retry logic to navigator test cleanup on Windows to handle
  EBUSY errors from unreleased file handles after move operations

Contributed on behalf of STMicroelectronics

Author: ndoschek

dev-packages/application-manager/src/expose-loader.ts

@@ -40,7 +40,10 @@ function exposeModule(modulePackage: { dir: string, name?: string }, resourcePat
     if (path.sep !== '/') {
         moduleName = moduleName.split(path.sep).join('/');
     }
-    return source + `\n;(globalThis['theia'] = globalThis['theia'] || {})['${moduleName}'] = this;\n`;
+    // Use `module.exports` with a fallback to `this` for compatibility with ESM modules.
+    // Webpack wraps ESM modules in arrow functions where `this` is `undefined`,
+    // but `module.exports` is available and points to the webpack exports object.
+    return source + `\n;(globalThis['theia'] = globalThis['theia'] || {})['${moduleName}'] = (typeof module === 'object' && module.exports) || this;\n`;
 }
 
 /**

dev-packages/private-test-setup/esm-loader-hooks.mjs

@@ -0,0 +1,34 @@
+// *****************************************************************************
+// Copyright (C) 2026 STMicroelectronics and others.
+//
+// This program and the accompanying materials are made available under the
+// terms of the Eclipse Public License v. 2.0 which is available at
+// http://www.eclipse.org/legal/epl-2.0.
+//
+// This Source Code may also be made available under the following Secondary
+// Licenses when the conditions for such availability set forth in the Eclipse
+// Public License v. 2.0 are satisfied: GNU General Public License, version 2
+// with the GNU Classpath Exception which is available at
+// https://www.gnu.org/software/classpath/license.html.
+//
+// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
+// *****************************************************************************
+
+// ESM loader hooks to handle non-JS file extensions (e.g. .css) that
+// are imported by ESM dependencies such as @theia/monaco-editor-core.
+// Without this, Node's ESM resolver throws ERR_UNKNOWN_FILE_EXTENSION
+// which causes mocha's import-then-require fallback to partially execute
+// test files before retrying, leading to duplicate side effects.
+
+const STYLE_EXTENSIONS = ['.css', '.scss', '.sass', '.less'];
+
+export function resolve(specifier, context, nextResolve) {
+    return nextResolve(specifier, context);
+}
+
+export function load(url, context, nextLoad) {
+    if (STYLE_EXTENSIONS.some(ext => url.endsWith(ext))) {
+        return { format: 'module', source: 'export default {};', shortCircuit: true };
+    }
+    return nextLoad(url, context);
+}

dev-packages/private-test-setup/test-setup.js

@@ -14,5 +14,13 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
 // *****************************************************************************
 
+// Register ESM loader hooks so that non-JS imports (e.g. .css files from
+// @theia/monaco-editor-core ESM bundles) are handled before mocha attempts
+// to load test files. Without this, Node's ESM resolver fails on .css
+// imports, and mocha's import→require fallback causes files to be partially
+// executed twice, leading to side-effect duplication.
+const { register } = require('node:module');
+register('./esm-loader-hooks.mjs', require('node:url').pathToFileURL(__filename));
+
 // Mock DragEvent as '@lumino/dragdrop' already requires it at require time
 global.DragEvent = class DragEvent { };

examples/api-tests/src/monaco-api.spec.js

@@ -14,14 +14,13 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
 // *****************************************************************************
 
-const { timeout } = require('@theia/core/lib/common/promise-util');
-const { IOpenerService } = require('@theia/monaco-editor-core/esm/vs/platform/opener/common/opener');
-
 // @ts-check
 describe('Monaco API', async function () {
     this.timeout(5000);
 
     const { assert } = chai;
+    const { timeout } = require('@theia/core/lib/common/promise-util');
+    const { IOpenerService } = require('@theia/monaco-editor-core/esm/vs/platform/opener/common/opener');
 
     const { EditorManager } = require('@theia/editor/lib/browser/editor-manager');
     const { WorkspaceService } = require('@theia/workspace/lib/browser/workspace-service');

examples/api-tests/src/navigator.spec.js

@@ -40,8 +40,21 @@ describe('Navigator', function () {
         await fileService.createFolder(targetUri);
     });
 
-    afterEach(async () => {
-        await fileService.delete(targetUri.parent, { fromUserGesture: false, useTrash: false, recursive: true });
+    afterEach(async function () {
+        // On Windows, file handles may not be released immediately after move/copy operations,
+        // causing EBUSY errors on cleanup. Retry with a short delay to handle this.
+        for (let attempt = 0; attempt < 3; attempt++) {
+            try {
+                await fileService.delete(targetUri.parent, { fromUserGesture: false, useTrash: false, recursive: true });
+                return;
+            } catch (e) {
+                if (attempt < 2) {
+                    await new Promise(resolve => setTimeout(resolve, 500));
+                } else {
+                    throw e;
+                }
+            }
+        }
     });
 
     /** @type {Array<['copy' | 'move', boolean]>} */

examples/api-tests/src/scm.spec.js

@@ -14,12 +14,11 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
 // *****************************************************************************
 
-const { timeout } = require('@theia/core/lib/common/promise-util');
-
 // @ts-check
 describe('SCM', function () {
 
     const { assert } = chai;
+    const { timeout } = require('@theia/core/lib/common/promise-util');
 
     const { HostedPluginSupport } = require('@theia/plugin-ext/lib/hosted/browser/hosted-plugin');
     const Uri = require('@theia/core/lib/common/uri');

examples/playwright/src/tests/theia-notebook-editor.test.ts

@@ -231,7 +231,7 @@ test.describe('Theia Notebook Cell interaction', () => {
         // second cell is selected after creation
         expect(await secondCell.isSelected()).toBe(true);
         // select cell above
-        await editor.page.keyboard.type('second cell');
+        await editor.page.keyboard.insertText('second cell');
         await secondCell.editor.page.keyboard.press('ArrowUp');
         expect(await cell.isSelected()).toBe(true);
 
@@ -306,7 +306,7 @@ test.describe('Theia Notebook Cell interaction', () => {
         await cell.selectCell();
         await cell.page.keyboard.press('l');
         // NOTE: div.line-numbers is not visible
-        await cell.editor.locator.locator('.overflow-guard > div.line-numbers').waitFor({ state: 'attached' });
+        await cell.editor.locator.locator('.margin-view-overlays .line-numbers').waitFor({ state: 'attached' });
     });
 
     test('Check Collapse output switch `o` works', async () => {

examples/playwright/src/theia-monaco-editor.ts

@@ -14,7 +14,7 @@
 // SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
 // *****************************************************************************
 
-import { ElementHandle, Locator } from '@playwright/test';
+import { ElementHandle, Locator, Page } from '@playwright/test';
 import { TheiaPageObject } from './theia-page-object';
 import { TheiaApp } from './theia-app';
 
@@ -162,7 +162,29 @@ export class TheiaMonacoEditor extends TheiaPageObject {
     async addEditorText(text: string, lineNumber: number = 1): Promise<void> {
         const line = await this.line(lineNumber);
         await line?.click();
-        await this.page.keyboard.type(text);
+        await TheiaMonacoEditor.typeText(this.page, text);
+    }
+
+    /**
+     * Types text into a focused Monaco editor using `keyboard.insertText()`.
+     *
+     * Monaco 1.108+ uses the native EditContext API by default instead of a hidden textarea.
+     * `keyboard.type()` dispatches individual key events which are not reliably processed by EditContext,
+     * causing characters to be lost. `keyboard.insertText()` dispatches an `InputEvent` which is handled
+     * correctly by both the legacy textarea and the native EditContext input mechanisms.
+     *
+     * Newlines in the text are handled by pressing Enter between segments.
+     */
+    static async typeText(page: Page, text: string): Promise<void> {
+        const segments = text.split('\n');
+        for (let i = 0; i < segments.length; i++) {
+            if (i > 0) {
+                await page.keyboard.press('Enter');
+            }
+            if (segments[i].length > 0) {
+                await page.keyboard.insertText(segments[i]);
+            }
+        }
     }
 
     /**

examples/playwright/src/theia-text-editor.ts

@@ -50,7 +50,7 @@ export class TheiaTextEditor extends TheiaEditor {
     }
 
     protected async typeTextAndHitEnter(text: string): Promise<void> {
-        await this.page.keyboard.type(text);
+        await TheiaMonacoEditor.typeText(this.page, text);
         await this.page.keyboard.press('Enter');
     }
 
@@ -107,15 +107,15 @@ export class TheiaTextEditor extends TheiaEditor {
         await this.placeCursorInLine(existingLine);
         await this.page.keyboard.press('End');
         await this.page.keyboard.press('Enter');
-        await this.page.keyboard.type(newText);
+        await TheiaMonacoEditor.typeText(this.page, newText);
     }
 
     async addTextToNewLineAfterLineByLineNumber(lineNumber: number, newText: string): Promise<void> {
         const existingLine = await this.monacoEditor.line(lineNumber);
         await this.placeCursorInLine(existingLine);
         await this.page.keyboard.press('End');
         await this.page.keyboard.press('Enter');
-        await this.page.keyboard.type(newText);
+        await TheiaMonacoEditor.typeText(this.page, newText);
     }
 
     protected async selectLine(lineLocator: Locator | undefined): Promise<void> {