Merge pull request #7700 from nextcloud/test/yjs_pending_structs

test: detect out of sync state and recovery via yjs pendingStructs

Author: mejo-

src/tests/fixtures/steps_two_clients.js

@@ -0,0 +1,13 @@
+// 10 steps each inserting one character ("abcdefghij"), alternating between two clients
+export default [
+	["AAI+AgPir\/+VDAAoAAAAA2RpcgF3A2x0cgcAAAAGBADir\/+VDAEBYQEAAAcBB2RlZmF1bHQDCXBhcmFncmFwaAA="],
+	["AAISAQGa2Iz7AwCE4q\/\/lQwCAWIA"],
+	["AAISAQHir\/+VDAOEmtiM+wMAAWMA"],
+	["AAISAQGa2Iz7AwGE4q\/\/lQwDAWQA"],
+	["AAISAQHir\/+VDASEmtiM+wMBAWUA"],
+	["AAISAQGa2Iz7AwKE4q\/\/lQwEAWYA"],
+	["AAISAQHir\/+VDAWEmtiM+wMCAWcA"],
+	["AAISAQGa2Iz7AwOE4q\/\/lQwFAWgA"],
+	["AAISAQHir\/+VDAaEmtiM+wMDAWkA"],
+	["AAISAQGa2Iz7AwSE4q\/\/lQwGAWoA"],
+]

src/tests/yjs.spec.js

@@ -3,12 +3,16 @@
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
+import { Collaboration } from '@tiptap/extension-collaboration'
 import * as decoding from 'lib0/decoding'
 import * as encoding from 'lib0/encoding'
 import * as syncProtocol from 'y-protocols/sync'
 import { Doc, encodeStateAsUpdate } from 'yjs'
+import { createRichEditor } from '../EditorFactory.js'
+import { createMarkdownSerializer } from '../extensions/Markdown.js'
 import { decodeArrayBuffer } from '../helpers/base64.ts'
 import recorded from './fixtures/recorded.js'
+import stepsTwoClients from './fixtures/steps_two_clients.js'
 
 describe('recorded session', () => {
 	const flattened = recorded.flat()
@@ -139,4 +143,44 @@ describe('recorded session', () => {
 		expect(replies.length).toBe(0)
 		expect(size(replies)).toBe(0)
 	})
+
+	test('detecting out of sync due to missing step via pending structs', () => {
+		// 10 steps each inserting one character, alternating between two clients
+		const syncSteps = stepsTwoClients.flat()
+		const fullDocumentContent = 'abcdefghij'
+		// Remove steps 2-5 from syncSteps and store them in missingSteps
+		const missingSteps = syncSteps.splice(1, 4)
+
+		// Create editor to access the content of the ydoc
+		const ydoc = new Doc()
+		const tiptap = createRichEditor({
+			extensions: [Collaboration.configure({ document: ydoc })],
+		})
+		const serializer = createMarkdownSerializer(tiptap.schema)
+
+		// Apply steps 1 and 6-10 (steps 2-5 are missing)
+		// Pending structs detected and only first charcter visible in content
+		syncSteps.map((step) => processStep(ydoc, step))
+		expect(ydoc.store.pendingStructs).not.toBeNull()
+		expect(serializer.serialize(tiptap.state.doc)).toEqual(
+			fullDocumentContent.slice(0, 1),
+		)
+
+		// Apply missing steps 2-5
+		for (const [i, step] of missingSteps.entries()) {
+			processStep(ydoc, step)
+			if (i < missingSteps.length - 1) {
+				// Each step except the last, one more character gets visible in content
+				expect(ydoc.store.pendingStructs).not.toBeNull()
+				expect(serializer.serialize(tiptap.state.doc)).toEqual(
+					fullDocumentContent.slice(0, i + 2),
+				)
+			}
+		}
+
+		// After all missing steps got applied, content is complete and no pending structs detected anymore
+		expect(ydoc.store.pendingStructs).toBeNull()
+		expect(serializer.serialize(tiptap.state.doc)).toEqual(fullDocumentContent)
+		tiptap.destroy()
+	})
 })