msglist: Set unreads.oldUnreadsMissing to false on batched mark-all-a…

…s-read

lib/widgets/message_list.dart

@@ -366,14 +366,24 @@ class MarkAsReadWidget extends StatelessWidget {
       await showErrorDialog(context: context,
         title: zulipLocalizations.errorMarkAsReadFailedTitle,
         message: e.toString());
+      return;
+    }
+    if (!context.mounted) return;
+    if (narrow == const AllMessagesNarrow()) {
+      // We've learned that the mark-all-as-read work succeeded, so we know
+      // there can't be ancient unreads we don't know about. Update the
+      // Unreads model to reflect that.
+      //
+      // [Unreads] is supposed to do this naturally, in
+      // handleUpdateMessageFlagsEvent. That's based on the documented behavior
+      // that a completed mark-all-as-read task gets signaled by `all: true` on
+      // the [UpdateMessageFlagsAddEvent]. But when using this new batch-
+      // processing protocol, it seems clients have to track progress and
+      // success themselves; the event from the last batch is unmarked.
+      // Discussion:
+      //   <https://chat.zulip.org/#narrow/stream/243-mobile-team/topic/flutter.3A.20Mark-as-read/near/1680275>
+      PerAccountStoreWidget.of(context).unreads.oldUnreadsMissing = false;
     }
-    // TODO: clear Unreads.oldUnreadsMissing when `narrow` is [AllMessagesNarrow]
-    //   In the rare case that the user had more than 50K total unreads
-    //   on the server, the client won't have known about all of them;
-    //   this was communicated to the client via `oldUnreadsMissing`.
-    //
-    //   However, since we successfully marked **everything** as read,
-    //   we know that we now have a correct data set of unreads.
   }
 
   @override

test/widgets/message_list_test.dart

@@ -570,6 +570,23 @@ void main() {
             });
       });
 
+      testWidgets('markNarrowAsRead on mark-all-as-read when Unreads.oldUnreadsMissing: true', (tester) async {
+        const narrow = AllMessagesNarrow();
+        await setupMessageListPage(tester,
+          narrow: narrow, messages: [message], unreadMsgs: unreadMsgs);
+        check(isMarkAsReadButtonVisible(tester)).isTrue();
+        store.unreads.oldUnreadsMissing = true;
+
+        final connection = store.connection as FakeApiConnection;
+        connection.prepare(json: UpdateMessageFlagsForNarrowResult(
+          processedCount: 11, updatedCount: 3,
+          firstProcessedId: null, lastProcessedId: null,
+          foundOldest: true, foundNewest: true).toJson());
+        await tester.tap(find.byType(MarkAsReadWidget));
+        await tester.pumpAndSettle();
+        check(store.unreads.oldUnreadsMissing).isFalse();
+      });
+
       testWidgets('markNarrowAsRead on invalid response', (WidgetTester tester) async {
         final zulipLocalizations = GlobalLocalizations.zulipLocalizations;
         final narrow = TopicNarrow.ofMessage(message);