sync_settings_ui 0.5.2: cancelled backup is not success

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WzxdWXTUM9dpnCS2wtFkx4

sync_settings_ui/lib/src/backup_slot.dart

@@ -1,5 +1,14 @@
 import 'package:data_transfer_flutter/data_transfer_flutter.dart';
 
+/// Thrown by a [BackupSlot] callback when the user dismissed the file dialog.
+///
+/// Not a failure: [SyncSettingsScreen] clears its status line instead of
+/// claiming success or showing an error.
+class BackupCancelled implements Exception {
+  /// Creates the signal.
+  const BackupCancelled();
+}
+
 /// An injectable local export/import delegate for [SyncSettingsScreen]'s
 /// optional "Backup" section.
 ///
@@ -24,7 +33,8 @@ class BackupSlot {
   /// Export saves `build()` as [fileName] to device storage (system Save-as
   /// on Android/iOS, a save dialog on desktop, a download on web). Import
   /// lets the user pick a JSON file and hands the decoded object to
-  /// [restore]; a cancelled picker restores nothing.
+  /// [restore]. A dismissed dialog throws [BackupCancelled] (and a cancelled
+  /// picker restores nothing).
   factory BackupSlot.json({
     required String label,
     required String fileName,
@@ -33,11 +43,13 @@ class BackupSlot {
   }) => BackupSlot(
     label: label,
     export: () async {
-      await exportJson(fileName: fileName, json: await build());
+      final saved = await exportJson(fileName: fileName, json: await build());
+      if (!saved) throw const BackupCancelled();
     },
     import: () async {
       final json = await pickJson();
-      if (json != null) await restore(json);
+      if (json == null) throw const BackupCancelled();
+      await restore(json);
     },
   );
 

sync_settings_ui/lib/src/sync_settings_screen.dart

@@ -123,6 +123,8 @@ class _SyncSettingsScreenState extends State<SyncSettingsScreen> {
     try {
       await backup.export();
       if (mounted) setState(() => _status = 'Exported ${backup.label}.');
+    } on BackupCancelled {
+      if (mounted) setState(() => _status = null);
     } on Exception catch (error) {
       if (mounted) setState(() => _status = 'Export failed: $error');
     }
@@ -132,6 +134,8 @@ class _SyncSettingsScreenState extends State<SyncSettingsScreen> {
     try {
       await backup.import();
       if (mounted) setState(() => _status = 'Imported ${backup.label}.');
+    } on BackupCancelled {
+      if (mounted) setState(() => _status = null);
     } on Exception catch (error) {
       if (mounted) setState(() => _status = 'Import failed: $error');
     }

sync_settings_ui/pubspec.yaml

@@ -5,7 +5,7 @@ description: >-
   injected closures -- no keystore or platform plugin access lives in this
   package itself.
 publish_to: 'none'
-version: 0.5.1
+version: 0.5.2
 
 environment:
   sdk: ^3.12.2

sync_settings_ui/test/backup_slot_test.dart

@@ -70,15 +70,28 @@ void main() {
         restore: (_) async => called = true,
       );
 
-      await slot.import();
+      await expectLater(slot.import(), throwsA(isA<BackupCancelled>()));
 
       expect(called, isFalse);
     });
+
+    test('a cancelled save dialog reports the cancellation', () async {
+      fake.acceptSave = false;
+      final slot = BackupSlot.json(
+        label: 'inventory',
+        fileName: 'inv.json',
+        build: () async => {'items': 3},
+        restore: (_) async {},
+      );
+
+      await expectLater(slot.export(), throwsA(isA<BackupCancelled>()));
+    });
   });
 }
 
 class _FakePlatform implements DataTransferPlatform {
   String? picked;
+  bool acceptSave = true;
   final saved = <(String, String)>[];
 
   @override
@@ -88,7 +101,7 @@ class _FakePlatform implements DataTransferPlatform {
     String mimeType = 'application/json',
   }) async {
     saved.add((fileName, text));
-    return true;
+    return acceptSave;
   }
 
   @override

sync_settings_ui/test/sync_settings_screen_backup_test.dart

@@ -17,6 +17,38 @@ Widget _wrap(Widget child) => MaterialApp(home: child);
 
 void main() {
   group('Backup section', () {
+    testWidgets('a cancelled export or import claims no success', (
+      tester,
+    ) async {
+      await tester.pumpWidget(
+        _wrap(
+          SyncSettingsScreen(
+            accountLoader: () async => null,
+            accountSaver: (_) async {},
+            accountClearer: () async {},
+            sessionProbe: () async => false,
+            firebaseFactory: () async => null,
+            backup: BackupSlot(
+              label: 'notes',
+              export: () async => throw const BackupCancelled(),
+              import: () async => throw const BackupCancelled(),
+            ),
+          ),
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      await tester.tap(find.text('Export notes'));
+      await tester.pumpAndSettle();
+      expect(find.text('Exported notes.'), findsNothing);
+      expect(find.textContaining('failed'), findsNothing);
+
+      await tester.tap(find.text('Import notes'));
+      await tester.pumpAndSettle();
+      expect(find.text('Imported notes.'), findsNothing);
+      expect(find.textContaining('failed'), findsNothing);
+    });
+
     testWidgets('omitted entirely when backup is null', (tester) async {
       await tester.pumpWidget(
         _wrap(