test(playwright): Add regression test for CJK IME input as first character

Signed-off-by: Jonas <jonas@freesources.org>

Author: mejo-

playwright/e2e/ime-input.spec.ts

@@ -0,0 +1,66 @@
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+// Ideas taken from https://github.com/microsoft/playwright/issues/5777 and https://github.com/slab/quill/commit/0ea789f95fc4956287b3995f9495aafa367d4190
+
+import { type Locator, expect, mergeTests } from '@playwright/test'
+import { test as editorTest } from '../support/fixtures/editor'
+import { test as uploadFileTest } from '../support/fixtures/upload-file'
+
+const test = mergeTests(editorTest, uploadFileTest)
+
+test.beforeEach(async ({ open }) => {
+	await open()
+})
+
+let composingData = ''
+async function withKeyboardEvents(
+	el: Locator,
+	key: string,
+	callback: () => Promise<void>,
+) {
+	composingData += key
+	await el.dispatchEvent('keydown', { key })
+	await callback()
+	await el.dispatchEvent('keyup', { key })
+}
+
+test('Input Chinese character via IME at beginning of paragraph works', async ({
+	browserName,
+	editor,
+	page,
+}) => {
+	test.skip(
+		browserName !== 'chromium',
+		'IME testing is currently only implemented in Chromium API',
+	)
+
+	// Get developer tools API
+	const client = await page.context().newCDPSession(page)
+
+	await editor.content.focus()
+
+	await withKeyboardEvents(editor.content, 'w', async () => {
+		client.send('Input.imeSetComposition', {
+			selectionStart: composingData.length,
+			selectionEnd: composingData.length,
+			text: 'w',
+		})
+	})
+	await withKeyboardEvents(editor.content, 'o', async () => {
+		client.send('Input.imeSetComposition', {
+			selectionStart: composingData.length,
+			selectionEnd: composingData.length,
+			text: 'o',
+		})
+	})
+	await withKeyboardEvents(editor.content, 'Space', async () => {
+		client.send('Input.insertText', {
+			text: '我',
+		})
+	})
+
+	await expect(editor.content).toHaveText('我')
+})