subscription_list: Show @-mention marker when that applies

Fixes: zulip#747

lib/model/unreads.dart

@@ -223,6 +223,28 @@ class Unreads extends ChangeNotifier {
     }
   }
 
+  Set<int> get channelsWithUnreadMentions {
+    final channels = <int>{};
+    for (var messageId in mentions) {
+      final streamId = _reverseStreamsLookup[messageId]?.streamId;
+      if (streamId != null) {
+        channels.add(streamId);
+      }
+    }
+    return channels;
+  }
+
+  Set<int> get channelsWithUnmutedMentions {
+    final channels = <int>{};
+    for (var messageId in mentions) {
+      final info = _reverseStreamsLookup[messageId]!;
+      if (channelStore.isTopicVisible(info.streamId, info.topic)) {
+        channels.add(info.streamId);
+      }
+    }
+    return channels;
+  }
+
   void handleMessageEvent(MessageEvent event) {
     final message = event.message;
     if (message.flags.contains(MessageFlag.read)) {

lib/widgets/subscription_list.dart

@@ -185,16 +185,24 @@ class _SubscriptionList extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final channelsWithMentions = unreadsModel!.channelsWithUnreadMentions;
+    final channelsWithUnmutedMentions = unreadsModel!.channelsWithUnmutedMentions;
     return SliverList.builder(
       itemCount: subscriptions.length,
       itemBuilder: (BuildContext context, int index) {
         final subscription = subscriptions[index];
         final unreadCount = unreadsModel!.countInChannel(subscription.streamId);
         final showMutedUnreadBadge = unreadCount == 0
           && unreadsModel!.countInChannelNarrow(subscription.streamId) > 0;
+        final hasMentions = channelsWithMentions.contains(subscription.streamId);
+        final hasOnlyMutedMentions = !subscription.isMuted
+          && channelsWithMentions.contains(subscription.streamId)
+          && !channelsWithUnmutedMentions.contains(subscription.streamId);
         return SubscriptionItem(subscription: subscription,
           unreadCount: unreadCount,
-          showMutedUnreadBadge: showMutedUnreadBadge);
+          showMutedUnreadBadge: showMutedUnreadBadge,
+          hasMentions: hasMentions,
+          hasOnlyMutedMentions: hasOnlyMutedMentions);
     });
   }
 }
@@ -206,11 +214,15 @@ class SubscriptionItem extends StatelessWidget {
     required this.subscription,
     required this.unreadCount,
     required this.showMutedUnreadBadge,
+    required this.hasMentions,
+    required this.hasOnlyMutedMentions,
   });
 
   final Subscription subscription;
   final int unreadCount;
   final bool showMutedUnreadBadge;
+  final bool hasMentions;
+  final bool hasOnlyMutedMentions;
 
   @override
   Widget build(BuildContext context) {
@@ -258,7 +270,7 @@ class SubscriptionItem extends StatelessWidget {
                   subscription.name)))),
           if (hasUnreads) ...[
             const SizedBox(width: 12),
-            // TODO(#747) show @-mention indicator when it applies
+            AtMentionMarker(muted: !subscription.isMuted && hasOnlyMutedMentions),
             Opacity(
               opacity: opacity,
               child: UnreadCountBadge(
@@ -267,7 +279,7 @@ class SubscriptionItem extends StatelessWidget {
                 bold: true)),
           ] else if (showMutedUnreadBadge) ...[
             const SizedBox(width: 12),
-            // TODO(#747) show @-mention indicator when it applies
+            if (hasMentions) const AtMentionMarker(muted: true),
             const MutedUnreadBadge(),
           ],
           const SizedBox(width: 16),

test/model/unreads_test.dart

@@ -326,6 +326,48 @@ void main() {
           });
         }
       });
+
+      test('channelsWithUnreadMentions', () {
+        final stream1 = eg.stream();
+        final stream2 = eg.stream();
+
+        prepare();
+        fillWithMessages([
+          eg.streamMessage(stream: stream1, flags: [MessageFlag.mentioned]),
+          eg.streamMessage(stream: stream1, flags: []),
+          eg.streamMessage(stream: stream2, flags: []),
+        ]);
+
+        check(model.channelsWithUnreadMentions.single).equals(stream1.streamId);
+      });
+
+      test('channelsWithUnmutedMentions', () async {
+        final stream1 = eg.stream();
+        final stream2 = eg.stream();
+        final stream3 = eg.stream();
+        final streams = [stream1, stream2, stream3];
+
+        prepare();
+
+        await channelStore.addStreams(streams);
+        await channelStore.addSubscriptions([
+          eg.subscription(stream1),
+          eg.subscription(stream2),
+          eg.subscription(stream3, isMuted: true)]);
+
+        await channelStore.addUserTopic(stream1, 'a normal', UserTopicVisibilityPolicy.none);
+        await channelStore.addUserTopic(stream2, 'b muted', UserTopicVisibilityPolicy.muted);
+        await channelStore.addUserTopic(stream3, 'c normal', UserTopicVisibilityPolicy.none);
+
+
+        fillWithMessages([
+          eg.streamMessage(stream: stream1, flags: [MessageFlag.mentioned], topic: 'a normal'),
+          eg.streamMessage(stream: stream2, flags: [MessageFlag.mentioned], topic: 'b muted'),
+          eg.streamMessage(stream: stream3, flags: [MessageFlag.mentioned], topic: 'c normal'),
+        ]);
+
+        check(model.channelsWithUnmutedMentions.single).equals(stream1.streamId);
+      });
     });
 
     group('DM messages', () {

test/widgets/subscription_list_test.dart

@@ -316,4 +316,58 @@ void main() {
     checkStreamNameWght(mutedStreamWithUnmutedUnreads.name,     400);
     checkStreamNameWght(mutedStreamWithNoUnmutedUnreads.name,   400);
   });
+
+  group('@-mention marker', () {
+    Iterable<AtMentionMarker> getAtMentionMarkers(WidgetTester tester) {
+      return tester.widgetList<AtMentionMarker>(find.byType(AtMentionMarker));
+    }
+
+    testWidgets('is shown when subscription has unread mentions', (tester) async {
+      final streamWithMentions =   eg.stream();
+      final streamWithNoMentions = eg.stream();
+
+      await setupStreamListPage(tester,
+        subscriptions: [
+          eg.subscription(streamWithMentions),
+          eg.subscription(streamWithNoMentions),
+        ],
+        userTopics: [
+          eg.userTopicItem(streamWithMentions,   'a', UserTopicVisibilityPolicy.none),
+          eg.userTopicItem(streamWithNoMentions, 'b', UserTopicVisibilityPolicy.muted),
+        ],
+        unreadMsgs: eg.unreadMsgs(
+          mentions: [1],
+          channels: [
+            UnreadChannelSnapshot(streamId: streamWithMentions.streamId,   topic: 'a', unreadMessageIds: [1]),
+            UnreadChannelSnapshot(streamId: streamWithNoMentions.streamId, topic: 'b', unreadMessageIds: [2]),
+          ]),
+      );
+
+      check(getAtMentionMarkers(tester)).single;
+    });
+
+    testWidgets('is muted when subscription has only muted mentions', (tester) async {
+      final streamWithMentions =          eg.stream();
+      final streamWithOnlyMutedMentions = eg.stream();
+
+      await setupStreamListPage(tester,
+        subscriptions: [
+          eg.subscription(streamWithMentions),
+          eg.subscription(streamWithOnlyMutedMentions, isMuted: true),
+        ],
+        userTopics: [
+          eg.userTopicItem(streamWithMentions,          'a', UserTopicVisibilityPolicy.none),
+          eg.userTopicItem(streamWithOnlyMutedMentions, 'b', UserTopicVisibilityPolicy.none),
+        ],
+        unreadMsgs: eg.unreadMsgs(
+          mentions: [1, 2],
+          channels: [
+            UnreadChannelSnapshot(streamId: streamWithMentions.streamId,          topic: 'a', unreadMessageIds: [1]),
+            UnreadChannelSnapshot(streamId: streamWithOnlyMutedMentions.streamId, topic: 'b', unreadMessageIds: [2]),
+          ]),
+      );
+
+      check(getAtMentionMarkers(tester).map((e) => e.muted)).deepEquals([false, true]);
+    });
+  });
 }