fix(mobile): highlight hydrated thread target on query failure

Co-authored-by: Kenny Lopez <klopez4212@gmail.com>
Signed-off-by: Kenny Lopez <klopez4212@gmail.com>

mobile/lib/features/channels/thread_detail_page.dart

@@ -114,6 +114,11 @@ class ThreadDetailPage extends HookConsumerWidget {
     });
 
     final fetchedReplies = replyMessages.value;
+    // A terminal query error cannot produce a more authoritative list. Keep
+    // loading states provisional, but let the hydrated route snapshot drive
+    // the one-shot target jump when the relay query has definitively failed.
+    final canUseMessagesForInitialTarget =
+        fetchedReplies != null || replyMessages.hasError;
     final liveDeletionHidesHead = _isDeletedBy(
       liveChannelEvents,
       threadHead.id,
@@ -342,43 +347,53 @@ class ThreadDetailPage extends HookConsumerWidget {
       );
     }
 
-    useEffect(() {
-      final messageId = initialMessageId;
-      // Wait for the authoritative thread query before consuming the one-shot
-      // jump; the fallback main-timeline list can contain only the linked reply.
-      if (messageId == null || fetchedReplies == null) return null;
-      final chronologicalIndex = replies.indexWhere(
-        (reply) => reply.id == messageId,
-      );
-      final targetIndex = messageId == threadHead.id
-          ? headIndex
-          : chronologicalIndex < 0
-          ? null
-          : indexForReply(chronologicalIndex);
-      if (targetIndex == null || didJumpToInitialMessage.value) return null;
-      didJumpToInitialMessage.value = true;
-      initialTailSettle.abandon();
-      userOptedOutOfTailFollow.value = true;
-      userDragDetachedTailFollow.value = false;
-      tailIntent.schedule(
-        allowed: true,
-        revalidate: () =>
-            context.mounted &&
-            itemScrollController.isAttached &&
-            !tailIntent.isDragging,
-        action: () {
-          // The provisional route snapshot can make the linked reply look like
-          // the tail. This authoritative deep-link jump intentionally leaves
-          // the user at an older item, so it must opt out of follow-tail first.
-          tailIntent.detach();
-          followsThreadTail.value = false;
-          isAtThreadTail.value = false;
-          itemScrollController.jumpTo(index: targetIndex, alignment: 0.35);
-          initialHighlightTargetIndex.value = targetIndex;
-        },
-      );
-      return null;
-    }, [initialMessageId, fetchedReplies, replies.length]);
+    useEffect(
+      () {
+        final messageId = initialMessageId;
+        // Wait for either the authoritative thread query or a terminal query
+        // error before consuming the one-shot jump. During loading, the fallback
+        // main-timeline list can contain only the linked reply; after an error,
+        // that hydrated snapshot is the best available target list.
+        if (messageId == null || !canUseMessagesForInitialTarget) return null;
+        final chronologicalIndex = replies.indexWhere(
+          (reply) => reply.id == messageId,
+        );
+        final targetIndex = messageId == threadHead.id
+            ? headIndex
+            : chronologicalIndex < 0
+            ? null
+            : indexForReply(chronologicalIndex);
+        if (targetIndex == null || didJumpToInitialMessage.value) return null;
+        didJumpToInitialMessage.value = true;
+        initialTailSettle.abandon();
+        userOptedOutOfTailFollow.value = true;
+        userDragDetachedTailFollow.value = false;
+        tailIntent.schedule(
+          allowed: true,
+          revalidate: () =>
+              context.mounted &&
+              itemScrollController.isAttached &&
+              !tailIntent.isDragging,
+          action: () {
+            // The provisional route snapshot can make the linked reply look like
+            // the tail. This authoritative deep-link jump intentionally leaves
+            // the user at an older item, so it must opt out of follow-tail first.
+            tailIntent.detach();
+            followsThreadTail.value = false;
+            isAtThreadTail.value = false;
+            itemScrollController.jumpTo(index: targetIndex, alignment: 0.35);
+            initialHighlightTargetIndex.value = targetIndex;
+          },
+        );
+        return null;
+      },
+      [
+        initialMessageId,
+        canUseMessagesForInitialTarget,
+        fetchedReplies,
+        replies.length,
+      ],
+    );
 
     useEffect(
       () {

mobile/test/features/channels/channel_detail_page_test.dart

@@ -193,6 +193,7 @@ Widget _buildTestable({
   Map<String, Future<List<NostrEvent>>> pendingThreadReplies = const {},
   TextScaler textScaler = TextScaler.noScaling,
   bool disableAnimations = false,
+  bool disableRetries = false,
   RelaySessionNotifier? relaySessionNotifier,
   http.Client? mediaClient,
   Widget? home,
@@ -203,6 +204,7 @@ Widget _buildTestable({
   final fakeMessagesNotifier =
       messagesNotifier ?? _FakeMessagesNotifier(messages);
   return ProviderScope(
+    retry: disableRetries ? (_, _) => null : null,
     overrides: [
       channelMessagesProvider(
         _channelId,
@@ -4469,6 +4471,68 @@ void main() {
       expect(enteringDecoration.color!.a, lessThan(0.12 * 0.4));
     });
 
+    testWidgets('highlights a hydrated target after the thread query fails', (
+      tester,
+    ) async {
+      final root = _textMsg(
+        id: 'root',
+        pubkey: 'alice',
+        content: 'Thread root',
+        createdAt: 1000,
+      );
+      final target = _textMsg(
+        id: 'target',
+        pubkey: 'bob',
+        content: 'Hydrated target',
+        createdAt: 1100,
+        extraTags: const [
+          ['e', 'root', '', 'reply'],
+        ],
+      );
+      final timelineMessages = formatTimeline([root, target]);
+      final replyCompleter = Completer<List<NostrEvent>>();
+
+      await tester.pumpWidget(
+        _buildTestable(
+          messages: [root, target],
+          pendingThreadReplies: {'root': replyCompleter.future},
+          disableRetries: true,
+          users: const {
+            'alice': UserProfile(pubkey: 'alice', displayName: 'Alice'),
+            'bob': UserProfile(pubkey: 'bob', displayName: 'Bob'),
+          },
+          home: ThreadDetailPage(
+            threadHead: timelineMessages.first,
+            allMessages: timelineMessages,
+            channelId: _testChannel.id,
+            currentPubkey: null,
+            isMember: true,
+            isArchived: false,
+            initialMessageId: 'target',
+          ),
+        ),
+      );
+      await tester.pumpAndSettle();
+
+      final targetFinder = find.byKey(const ValueKey('thread-message-target'));
+      expect(targetFinder, findsOneWidget);
+      final loadingDecoration =
+          tester.widget<DecoratedBox>(targetFinder).decoration as BoxDecoration;
+      expect(loadingDecoration.color, Colors.transparent);
+
+      replyCompleter.completeError(Exception('thread query failed'));
+      for (var i = 0; i < 8; i++) {
+        await tester.pump();
+      }
+      await tester.pump(const Duration(milliseconds: 50));
+      await tester.pump(const Duration(milliseconds: 150));
+
+      final highlightedDecoration =
+          tester.widget<DecoratedBox>(targetFinder).decoration as BoxDecoration;
+      expect(highlightedDecoration.color!.a, greaterThan(0));
+      expect(highlightedDecoration.color!.a, lessThan(0.12 * 0.4));
+    });
+
     testWidgets('opens a nested reply in its direct-parent thread', (
       tester,
     ) async {