unreads: In @-mentions count, exclude messages in muted DM conversations

Fixes #2026.

Author: chrisbobbe

lib/model/message_list.dart

@@ -691,6 +691,9 @@ class MessageListView with ChangeNotifier, _MessageSequence {
         return true;
 
       case MentionsNarrow():
+        // If changing this, consider whether [Unreads.countInMentionsNarrow]
+        // should be changed correspondingly, so the message-list view matches
+        // the unread-count badge.
       case StarredMessagesNarrow():
       case KeywordSearchNarrow():
         if (message.conversation case DmConversation(:final allRecipientIds)) {

lib/model/unreads.dart

@@ -220,7 +220,30 @@ class Unreads extends PerAccountStoreBase with ChangeNotifier {
 
   int countInDmNarrow(DmNarrow narrow) => dms[narrow]?.length ?? 0;
 
-  int countInMentionsNarrow() => mentions.length;
+  /// The unread count for the mentions narrow.
+  ///
+  /// This excludes DM messages in conversations that are considered muted,
+  /// by [UserStore.shouldMuteDmConversation].
+  // If changing which messages to exclude, consider whether the @-mentions
+  // view should change its "is-message-visible" code correspondingly,
+  // so the unread-count badge matches what you see in that view.
+  // TODO: deduplicate "is-message-visible" code
+  //   between [Unreads] and [MessageListView]?
+  // TODO(#370): maintain this count incrementally, rather than recomputing from scratch
+  int countInMentionsNarrow() {
+    int c = 0;
+    for (final messageId in mentions) {
+      final narrow = locatorMap[messageId];
+      if (narrow == null) continue; // TODO(log)
+      switch (narrow) {
+        case DmNarrow():
+          if (channelStore.shouldMuteDmConversation(narrow)) continue;
+        case TopicNarrow():
+      }
+      c++;
+    }
+    return c;
+  }
 
   // TODO: Implement unreads handling.
   int countInStarredMessagesNarrow() => 0;

test/model/unreads_test.dart

@@ -254,13 +254,66 @@ void main() {
       test('smoke', () async {
         final stream = eg.stream();
         prepare();
+        await store.addUser(eg.otherUser);
         await store.addStream(stream);
         fillWithMessages([
           eg.streamMessage(stream: stream, flags: []),
           eg.streamMessage(stream: stream, flags: [MessageFlag.mentioned]),
           eg.streamMessage(stream: stream, flags: [MessageFlag.wildcardMentioned]),
+          eg.dmMessage(from: eg.otherUser, to: [eg.selfUser], flags: [MessageFlag.mentioned]),
+          eg.dmMessage(from: eg.otherUser, to: [eg.selfUser], flags: [MessageFlag.wildcardMentioned]),
         ]);
-        check(model.countInMentionsNarrow()).equals(2);
+        check(model.countInMentionsNarrow()).equals(4);
+      });
+
+      test('excludes unreads in muted DM conversations', () async {
+        // Regression test for https://github.com/zulip/zulip-flutter/issues/2026
+        prepare();
+        await store.addUser(eg.otherUser);
+        await store.setMutedUsers([eg.otherUser.userId]);
+
+        fillWithMessages([
+          eg.dmMessage(from: eg.otherUser, to: [eg.selfUser], flags: [MessageFlag.mentioned]),
+        ]);
+        check(model.countInMentionsNarrow()).equals(0);
+      });
+
+      test('not affected by DM sender being unknown', () async {
+        prepare();
+        final unknownUser = eg.user();
+        check(store.getUser(unknownUser.userId)).isNull();
+
+        fillWithMessages([
+          eg.dmMessage(from: unknownUser, to: [eg.selfUser], flags: [MessageFlag.mentioned]),
+        ]);
+        check(model.countInMentionsNarrow()).equals(1);
+      });
+
+      test('not affected by channel being unknown/unsubscribed/muted, nor topic being muted', () async {
+        prepare();
+
+        final channel1 = eg.stream(); // unknown
+
+        final channel2 = eg.stream(); // unsubscribed
+        await store.addStream(channel2);
+        check(store.subscriptions[channel2.streamId]).isNull();
+
+        final channel3 = eg.stream(); // muted
+        await store.addStream(channel3);
+        await store.addSubscription(eg.subscription(channel3, isMuted: true));
+
+        final channel4 = eg.stream(); // unmuted, containing muted topic
+        await store.addStream(channel4);
+        await store.addSubscription(eg.subscription(channel4, isMuted: false));
+        await store.setUserTopic(channel4, 'a', UserTopicVisibilityPolicy.muted);
+
+        fillWithMessages([
+          eg.streamMessage(stream: channel1,             flags: [MessageFlag.mentioned]),
+          eg.streamMessage(stream: channel2,             flags: [MessageFlag.mentioned]),
+          eg.streamMessage(stream: channel3,             flags: [MessageFlag.mentioned]),
+          eg.streamMessage(stream: channel4, topic: 'a', flags: [MessageFlag.mentioned]),
+        ]);
+        check(model.countInMentionsNarrow()).equals(4);
       });
     });