fix: prevent Enter key from re-running a settled search (#473)

When results were already showing for a query, pressing Enter again
re-triggered an IMAP search unnecessarily. This could cause a brief
loading spinner and, if the server returned results in a different
order, the user would tap what looked like the first result but open
the wrong email.

Tracks _lastSettledQuery; _runSearch is a no-op when results are
already settled for the same query.

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

lib/ui/screens/email_list_screen.dart

@@ -55,6 +55,10 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
   // generation has advanced (prevents out-of-order IMAP responses from
   // overwriting fresh results with results for an older query).
   int _searchGeneration = 0;
+  // The query whose results are currently settled in _searchResults.
+  // Used to skip redundant re-runs when the user presses Enter on an
+  // already-settled search (issue #473).
+  String? _lastSettledQuery;
   bool get _selecting =>
       _selectedThreadIds.isNotEmpty || _selectedSearchIds.isNotEmpty;
 
@@ -66,6 +70,7 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
         setState(() {
           _searchResults = null;
           _searchLoading = false;
+          _lastSettledQuery = null;
         });
       }
     });
@@ -122,8 +127,17 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
   }
 
   Future<void> _runSearch(String query) async {
-    if (query.trim().isEmpty) {
-      setState(() => _searchResults = null);
+    final q = query.trim();
+    if (q.isEmpty) {
+      setState(() {
+        _searchResults = null;
+        _lastSettledQuery = null;
+      });
+      return;
+    }
+    // Skip if results are already settled for this exact query — prevents the
+    // Enter key from re-triggering an IMAP search that already completed.
+    if (_searchResults != null && !_searchLoading && q == _lastSettledQuery) {
       return;
     }
     final generation = ++_searchGeneration;
@@ -131,9 +145,12 @@ class _EmailListScreenState extends ConsumerState<EmailListScreen> {
     try {
       final results = await ref
           .read(emailRepositoryProvider)
-          .searchEmails(widget.accountId, widget.mailboxPath, query.trim());
+          .searchEmails(widget.accountId, widget.mailboxPath, q);
       if (mounted && generation == _searchGeneration) {
-        setState(() => _searchResults = results);
+        setState(() {
+          _searchResults = results;
+          _lastSettledQuery = q;
+        });
       }
     } finally {
       if (mounted && generation == _searchGeneration) {

test/widget/email_list_screen_test.dart

@@ -554,6 +554,69 @@ void main() {
       },
     );
 
+    testWidgets(
+      'pressing Enter on already-settled search does not re-run search (issue #473)',
+      (tester) async {
+        final email1 = testEmail(id: 'acc-1:1', subject: 'Alpha Match');
+        final email2 = testEmail(id: 'acc-1:2', subject: 'Beta Match');
+
+        var searchCallCount = 0;
+
+        await tester.pumpWidget(
+          buildApp(
+            initialLocation: '/accounts/acc-1/mailboxes/INBOX/emails',
+            overrides: [
+              accountRepositoryProvider.overrideWithValue(
+                FakeAccountRepository([kTestAccount]),
+              ),
+              mailboxRepositoryProvider.overrideWithValue(
+                FakeMailboxRepository(),
+              ),
+              emailRepositoryProvider.overrideWithValue(
+                FakeEmailRepository(
+                  onSearch: (_) async {
+                    searchCallCount++;
+                    return [email1, email2];
+                  },
+                  emailBody: const EmailBody(emailId: '', attachments: []),
+                ),
+              ),
+            ],
+          ),
+        );
+        await tester.pumpAndSettle();
+
+        // Run the initial search.
+        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);
+
+        final countAfterFirstSearch = searchCallCount;
+
+        // Re-focus the search bar (simulates user tapping back into the field
+        // with the keyboard still visible) and press Enter again on the same,
+        // already-settled query.
+        await tester.tap(find.byType(TextField));
+        await tester.pump();
+        await tester.testTextInput.receiveAction(TextInputAction.search);
+        await tester.pumpAndSettle();
+
+        // The search must NOT re-run; call count must not increase.
+        expect(
+          searchCallCount,
+          countAfterFirstSearch,
+          reason:
+              'Enter on settled results must not re-run the search (issue #473)',
+        );
+        // Results must still be visible — no loading spinner.
+        expect(find.byType(CircularProgressIndicator), findsNothing);
+        expect(find.text('Alpha Match'), findsOneWidget);
+      },
+    );
+
     testWidgets('deleting all search results pops back to previous screen', (
       tester,
     ) async {