Desktop: Resolves issue #12039: Checks whether there exists a deleted folder in order to determine if Trash is collapsible

.eslintignore

@@ -1158,6 +1158,7 @@ packages/lib/models/settings/settingValidations.js
 packages/lib/models/settings/types.js
 packages/lib/models/utils/areAllFoldersCollapsed.test.js
 packages/lib/models/utils/areAllFoldersCollapsed.js
+packages/lib/models/utils/getCanBeCollapsedFolderIds.test.js
 packages/lib/models/utils/getCanBeCollapsedFolderIds.js
 packages/lib/models/utils/getCollator.js
 packages/lib/models/utils/getConflictFolderId.js

.gitignore

@@ -1132,6 +1132,7 @@ packages/lib/models/settings/settingValidations.js
 packages/lib/models/settings/types.js
 packages/lib/models/utils/areAllFoldersCollapsed.test.js
 packages/lib/models/utils/areAllFoldersCollapsed.js
+packages/lib/models/utils/getCanBeCollapsedFolderIds.test.js
 packages/lib/models/utils/getCanBeCollapsedFolderIds.js
 packages/lib/models/utils/getCollator.js
 packages/lib/models/utils/getConflictFolderId.js

packages/lib/models/utils/getCanBeCollapsedFolderIds.test.ts

@@ -0,0 +1,28 @@
+import { setupDatabaseAndSynchronizer, switchClient } from '../../testing/test-utils';
+import Folder from '../Folder';
+import getCanBeCollapsedFolderIds from './getCanBeCollapsedFolderIds';
+
+describe('getCanBeCollapsedFolderIds', () => {
+
+	beforeEach(async () => {
+		await setupDatabaseAndSynchronizer(1);
+		await switchClient(1);
+	});
+
+	it('should tell if trash can be collapsed too', async () => {
+		const folder1 = await Folder.save({});
+		await Folder.save({ parent_id: folder1.id });
+		await Folder.save({ parent_id: folder1.id });
+
+		const folder2 = await Folder.save({ });
+		const folder2a = await Folder.save({ parent_id: folder2.id });
+		await Folder.save({ parent_id: folder2a.id });
+
+		expect(getCanBeCollapsedFolderIds(await Folder.all({ includeTrash: true }))).toHaveLength(3);
+
+		await Folder.delete(folder1.id, { toTrash: true, deleteChildren: true });
+
+		expect(getCanBeCollapsedFolderIds(await Folder.all({ includeTrash: true }))).toHaveLength(4);
+	});
+
+});

packages/lib/models/utils/getCanBeCollapsedFolderIds.ts

@@ -1,4 +1,5 @@
 import { FolderEntity } from '../../services/database/types';
+import { getTrashFolderId } from '../../services/trash';
 import Folder, { FolderEntityWithChildren } from '../Folder';
 
 export default (folders: FolderEntity[]) => {
@@ -17,5 +18,25 @@ export default (folders: FolderEntity[]) => {
 
 	processTree(tree);
 
+	// Logic to determine whether trash should be included in canBeCollapsedIds
+	// Loops over all folders recursively in case in the future a deleted folder remains child of a not deleted folder (and hence there is no deleted folder in 'tree').
+	const isTrashCollapsable = (folders: FolderEntityWithChildren[]) => {
+		for (const folder of folders) {
+			if (folder.deleted_time) {
+				canBeCollapsedIds.push(getTrashFolderId());
+				return;
+			}
+
+			if (folder.children.length) {
+				isTrashCollapsable(folder.children);
+			}
+		}
+	};
+
+	// Future proofing: if TrashFolder is already in canBeCollapsedIds do not add it again.
+	if (!(getTrashFolderId() in canBeCollapsedIds)) {
+		isTrashCollapsable(tree);
+	}
+
 	return canBeCollapsedIds;
 };