fix: discard stale search results when a newer query supersedes them

Concurrent IMAP searches were triggered on every keystroke via
`unawaited(_runSearch(...))`. A slower earlier search completing after
a faster later search would overwrite `_searchResults` with stale data,
causing the wrong email to open when tapping a result.

Fix: add a `_searchGeneration` counter incremented on each search start;
results are only applied when the generation matches (i.e. no newer
search was started since). Clearing the query also resets state
immediately without waiting for any in-flight request.

Added two widget tests:
- tapping the first of multiple search results opens the correct email
- stale results from a slower concurrent search are discarded

Fixes #467

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/ui/screens/email_list_screen.dart

@@ -50,6 +50,11 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
   // Pagination: number of threads currently requested from the DB.
   static const _pageSize = 50;
   int _limit = _pageSize;
+
+  // Incremented on every search start; stale completions are ignored when the
+  // generation has advanced (prevents out-of-order IMAP responses from
+  // overwriting fresh results with results for an older query).
+  int _searchGeneration = 0;
   bool get _selecting =>
       _selectedThreadIds.isNotEmpty || _selectedSearchIds.isNotEmpty;
 
@@ -121,14 +126,19 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
       setState(() => _searchResults = null);
       return;
     }
+    final generation = ++_searchGeneration;
     setState(() => _searchLoading = true);
     try {
       final results = await ref
           .read(emailRepositoryProvider)
           .searchEmails(widget.accountId, widget.mailboxPath, query.trim());
-      if (mounted) setState(() => _searchResults = results);
+      if (mounted && generation == _searchGeneration) {
+        setState(() => _searchResults = results);
+      }
     } finally {
-      if (mounted) setState(() => _searchLoading = false);
+      if (mounted && generation == _searchGeneration) {
+        setState(() => _searchLoading = false);
+      }
     }
   }
 

pubspec.lock

@@ -371,6 +371,14 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_launcher_icons:
+    dependency: "direct dev"
+    description:
+      name: flutter_launcher_icons
+      sha256: "10f13781741a2e3972126fae08393d3c4e01fa4cd7473326b94b72cf594195e7"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.14.4"
   flutter_lints:
     dependency: "direct dev"
     description:
@@ -562,6 +570,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "4.1.2"
+  image:
+    dependency: transitive
+    description:
+      name: image
+      sha256: f9881ff4998044947ec38d098bc7c8316ae1186fa786eddffdb867b9bc94dfce
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.8.0"
   integration_test:
     dependency: "direct dev"
     description: flutter

test/widget/email_list_screen_test.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
@@ -430,6 +432,128 @@ void main() {
       expect(find.text('Result email'), findsWidgets);
     });
 
+    testWidgets(
+      'tapping first of multiple search results opens the first email',
+      (tester) async {
+        final email1 = testEmail(id: 'acc-1:1', subject: 'Alpha Match');
+        final email2 = testEmail(id: 'acc-1:2', subject: 'Beta Match');
+        await tester.pumpWidget(
+          buildApp(
+            initialLocation: '/accounts/acc-1/mailboxes/INBOX/emails',
+            overrides: [
+              accountRepositoryProvider.overrideWithValue(
+                FakeAccountRepository([kTestAccount]),
+              ),
+              mailboxRepositoryProvider.overrideWithValue(
+                FakeMailboxRepository(),
+              ),
+              emailRepositoryProvider.overrideWithValue(
+                FakeEmailRepository(
+                  searchResults: [email1, email2],
+                  emailBody: const EmailBody(emailId: '', attachments: []),
+                ),
+              ),
+            ],
+          ),
+        );
+        await tester.pumpAndSettle();
+
+        await tester.enterText(find.byType(TextField), 'Match');
+        await tester.testTextInput.receiveAction(TextInputAction.search);
+        await tester.pumpAndSettle();
+
+        expect(find.text('Alpha Match'), findsOneWidget);
+        expect(find.text('Beta Match'), findsOneWidget);
+
+        // Tap the first result.
+        await tester.tap(find.text('Alpha Match'));
+        await tester.pumpAndSettle();
+
+        expect(find.byType(EmailDetailScreen), findsOneWidget);
+        // The detail AppBar title shows the first email's subject.
+        expect(
+          find.descendant(
+            of: find.byType(AppBar),
+            matching: find.text('Alpha Match'),
+          ),
+          findsOneWidget,
+        );
+        // The second email's subject must not appear in the detail view.
+        expect(
+          find.descendant(
+            of: find.byType(EmailDetailScreen),
+            matching: find.text('Beta Match'),
+          ),
+          findsNothing,
+        );
+      },
+    );
+
+    testWidgets(
+      'stale search results from a slower concurrent search are discarded',
+      (tester) async {
+        // Reproduces: user types quickly, triggering multiple concurrent IMAP
+        // searches. An older, slower search must not overwrite the results for
+        // the user's current query (issue #467).
+        final staleEmail = testEmail(id: 'acc-1:1', subject: 'Stale Result');
+        final freshEmail = testEmail(id: 'acc-1:2', subject: 'Fresh Result');
+
+        // The first search call is held open by a Completer; all subsequent
+        // calls resolve immediately with freshEmail.
+        final staleCompleter = Completer<List<Email>>();
+        var firstCall = true;
+
+        await tester.pumpWidget(
+          buildApp(
+            initialLocation: '/accounts/acc-1/mailboxes/INBOX/emails',
+            overrides: [
+              accountRepositoryProvider.overrideWithValue(
+                FakeAccountRepository([kTestAccount]),
+              ),
+              mailboxRepositoryProvider.overrideWithValue(
+                FakeMailboxRepository(),
+              ),
+              emailRepositoryProvider.overrideWithValue(
+                FakeEmailRepository(
+                  onSearch: (_) {
+                    if (firstCall) {
+                      firstCall = false;
+                      return staleCompleter.future;
+                    }
+                    return Future.value([freshEmail]);
+                  },
+                  emailBody: const EmailBody(emailId: '', attachments: []),
+                ),
+              ),
+            ],
+          ),
+        );
+        await tester.pumpAndSettle();
+
+        // Trigger the first (slow) search.
+        await tester.enterText(find.byType(TextField), 'slow');
+        await tester.testTextInput.receiveAction(TextInputAction.search);
+        // Do not pumpAndSettle yet — the slow search is still in flight.
+
+        // Trigger the second (fast) search by changing the query.
+        await tester.enterText(find.byType(TextField), 'fast');
+        await tester.testTextInput.receiveAction(TextInputAction.search);
+        await tester.pumpAndSettle(); // fast searches settle immediately
+
+        // The fresh results must be shown.
+        expect(find.text('Fresh Result'), findsOneWidget);
+        expect(find.text('Stale Result'), findsNothing);
+
+        // Now let the stale search complete.
+        staleCompleter.complete([staleEmail]);
+        await tester.pumpAndSettle();
+
+        // The stale results must NOT replace the fresh ones.
+        expect(find.text('Fresh Result'), findsOneWidget);
+        expect(find.text('Stale Result'), findsNothing);
+      },
+    );
+
     testWidgets('deleting all search results pops back to previous screen', (
       tester,
     ) async {

test/widget/helpers.dart

@@ -216,12 +216,17 @@ class FakeEmailRepository implements EmailRepository {
 
   final List<Email> _searchResults;
 
+  /// Optional override: when set, [searchEmails] calls this instead of
+  /// returning [_searchResults]. Useful for testing race-condition fixes.
+  final Future<List<Email>> Function(String query)? onSearch;
+
   FakeEmailRepository({
     List<Email>? emails,
     Email? emailDetail,
     EmailBody? emailBody,
     List<Email>? searchResults,
     String rawRfc822 = '',
+    this.onSearch,
   })  : _emails = emails ?? [],
         _emailDetail = emailDetail,
         _searchResults = searchResults ?? [],
@@ -274,7 +279,15 @@ class FakeEmailRepository implements EmailRepository {
       Stream.value(_emails.where((e) => e.threadId == threadId).toList());
 
   @override
-  Future<Email?> getEmail(String emailId) async => _emailDetail;
+  Future<Email?> getEmail(String emailId) async {
+    for (final e in _searchResults) {
+      if (e.id == emailId) return e;
+    }
+    for (final e in _emails) {
+      if (e.id == emailId) return e;
+    }
+    return _emailDetail;
+  }
 
   @override
   Future<EmailBody> getEmailBody(String emailId) async => _emailBody;
@@ -340,8 +353,10 @@ class FakeEmailRepository implements EmailRepository {
     String accountId,
     String mailboxPath,
     String query,
-  ) async =>
+  ) async {
-      _searchResults;
+    if (onSearch != null) return onSearch!(query);
+    return _searchResults;
+  }
 
   @override
   Future<List<Email>> searchEmailsGlobal(