general chat #2: support sending to empty topic from channel narrow, hide resolve/unresolve conditionally

lib/api/model/initial_snapshot.dart

@@ -85,6 +85,8 @@ class InitialSnapshot {
 
   final Uri? serverEmojiDataUrl; // TODO(server-6)
 
+  final String? realmEmptyTopicDisplayName; // TODO(server-10)
+
   @JsonKey(readValue: _readUsersIsActiveFallbackTrue)
   final List<User> realmUsers;
   @JsonKey(readValue: _readUsersIsActiveFallbackFalse)
@@ -138,6 +140,7 @@ class InitialSnapshot {
     required this.realmDefaultExternalAccounts,
     required this.maxFileUploadSizeMib,
     required this.serverEmojiDataUrl,
+    required this.realmEmptyTopicDisplayName,
     required this.realmUsers,
     required this.realmNonActiveUsers,
     required this.crossRealmBots,

lib/api/model/model.dart

@@ -690,7 +690,7 @@ extension type const TopicName(String _value) {
   /// so that UI code can identify when it needs to represent the topic
   /// specially in the way prescribed for "general chat".
   // TODO(#1250) carry out that plan
-  String get displayName => _value;
+  String? get displayName => _value.isEmpty ? null : _value;
 
   /// The key to use for "same topic as" comparisons.
   String canonicalize() => apiName.toLowerCase();

lib/api/route/channels.dart

@@ -7,8 +7,12 @@ part 'channels.g.dart';
 /// https://zulip.com/api/get-stream-topics
 Future<GetStreamTopicsResult> getStreamTopics(ApiConnection connection, {
   required int streamId,
+  bool? allowEmptyTopicName,
 }) {
-  return connection.get('getStreamTopics', GetStreamTopicsResult.fromJson, 'users/me/$streamId/topics', {});
+  assert(allowEmptyTopicName != false, '`allowEmptyTopicName` should only be true or null');
+  return connection.get('getStreamTopics', GetStreamTopicsResult.fromJson, 'users/me/$streamId/topics', {
+    if (allowEmptyTopicName != null) 'allow_empty_topic_name': allowEmptyTopicName,
+  });
 }
 
 @JsonSerializable(fieldRename: FieldRename.snake)

lib/api/route/events.dart

@@ -18,6 +18,7 @@ Future<InitialSnapshot> registerQueue(ApiConnection connection) {
       'user_avatar_url_field_optional': false, // TODO(#254): turn on
       'stream_typing_notifications': true,
       'user_settings_object': true,
+      'empty_topic_name': true,
     },
   });
 }

lib/api/route/messages.dart

@@ -16,9 +16,11 @@ part 'messages.g.dart';
 Future<Message?> getMessageCompat(ApiConnection connection, {
   required int messageId,
   bool? applyMarkdown,
+  bool? allowEmptyTopicName,
 }) async {
   final useLegacyApi = connection.zulipFeatureLevel! < 120;
   if (useLegacyApi) {
+    assert(allowEmptyTopicName == null);
     final response = await getMessages(connection,
       narrow: [ApiNarrowMessageId(messageId)],
       anchor: NumericAnchor(messageId),
@@ -37,6 +39,7 @@ Future<Message?> getMessageCompat(ApiConnection connection, {
       final response = await getMessage(connection,
         messageId: messageId,
         applyMarkdown: applyMarkdown,
+        allowEmptyTopicName: allowEmptyTopicName,
       );
       return response.message;
     } on ZulipApiException catch (e) {
@@ -57,10 +60,13 @@ Future<Message?> getMessageCompat(ApiConnection connection, {
 Future<GetMessageResult> getMessage(ApiConnection connection, {
   required int messageId,
   bool? applyMarkdown,
+  bool? allowEmptyTopicName,
 }) {
+  assert(allowEmptyTopicName != false, '`allowEmptyTopicName` should only be true or null');
   assert(connection.zulipFeatureLevel! >= 120);
   return connection.get('getMessage', GetMessageResult.fromJson, 'messages/$messageId', {
     if (applyMarkdown != null) 'apply_markdown': applyMarkdown,
+    if (allowEmptyTopicName != null) 'allow_empty_topic_name': allowEmptyTopicName,
   });
 }
 
@@ -88,8 +94,10 @@ Future<GetMessagesResult> getMessages(ApiConnection connection, {
   required int numAfter,
   bool? clientGravatar,
   bool? applyMarkdown,
+  bool? allowEmptyTopicName,
   // bool? useFirstUnreadAnchor // omitted because deprecated
 }) {
+  assert(allowEmptyTopicName != false, '`allowEmptyTopicName` should only be true or null');
   return connection.get('getMessages', GetMessagesResult.fromJson, 'messages', {
     'narrow': resolveApiNarrowForServer(narrow, connection.zulipFeatureLevel!),
     'anchor': RawParameter(anchor.toJson()),
@@ -98,6 +106,7 @@ Future<GetMessagesResult> getMessages(ApiConnection connection, {
     'num_after': numAfter,
     if (clientGravatar != null) 'client_gravatar': clientGravatar,
     if (applyMarkdown != null) 'apply_markdown': applyMarkdown,
+    if (allowEmptyTopicName != null) 'allow_empty_topic_name': allowEmptyTopicName,
   });
 }
 

lib/model/autocomplete.dart

@@ -904,7 +904,11 @@ class TopicAutocompleteView extends AutocompleteView<TopicAutocompleteQuery, Top
   Future<void> _fetch() async {
      assert(!_isFetching);
     _isFetching = true;
-    final result = await getStreamTopics(store.connection, streamId: streamId);
+    final result = await getStreamTopics(store.connection, streamId: streamId,
+      allowEmptyTopicName:
+        // TODO(server-10): simplify this condition away
+        store.zulipFeatureLevel >= 334 ? true : null,
+    );
     _topics = result.topics.map((e) => e.name);
     _isFetching = false;
     return _startSearch();
@@ -921,7 +925,7 @@ class TopicAutocompleteView extends AutocompleteView<TopicAutocompleteQuery, Top
   }
 
   TopicAutocompleteResult? _testTopic(TopicAutocompleteQuery query, TopicName topic) {
-    if (query.testTopic(topic)) {
+    if (query.testTopic(store, topic)) {
       return TopicAutocompleteResult(topic: topic);
     }
     return null;
@@ -939,10 +943,16 @@ class TopicAutocompleteView extends AutocompleteView<TopicAutocompleteQuery, Top
 class TopicAutocompleteQuery extends AutocompleteQuery {
   TopicAutocompleteQuery(super.raw);
 
-  bool testTopic(TopicName topic) {
+  bool testTopic(PerAccountStore store, TopicName topic) {
     // TODO(#881): Sort by match relevance, like web does.
+
+    if (topic.displayName == null) {
+      return store.realmEmptyTopicDisplayName.toLowerCase()
+        .contains(raw.toLowerCase());
+    }
+    // Skip this option if it matches the query exactly.
     return topic.displayName != raw
-      && topic.displayName.toLowerCase().contains(raw.toLowerCase());
+      && topic.displayName!.toLowerCase().contains(raw.toLowerCase());
   }
 
   @override

lib/model/message_list.dart

@@ -509,6 +509,9 @@ class MessageListView with ChangeNotifier, _MessageSequence {
       anchor: AnchorCode.newest,
       numBefore: kMessageListFetchBatchSize,
       numAfter: 0,
+      allowEmptyTopicName:
+        // TODO(server-10): simplify this condition away
+        store.zulipFeatureLevel >= 334 ? true : null,
     );
     if (this.generation > generation) return;
     _adjustNarrowForTopicPermalink(result.messages.firstOrNull);
@@ -581,6 +584,9 @@ class MessageListView with ChangeNotifier, _MessageSequence {
           includeAnchor: false,
           numBefore: kMessageListFetchBatchSize,
           numAfter: 0,
+          allowEmptyTopicName:
+            // TODO(server-10): simplify this condition away
+            store.zulipFeatureLevel >= 334 ? true : null,
         );
       } catch (e) {
         hasFetchError = true;

lib/model/store.dart

@@ -302,6 +302,7 @@ class PerAccountStore extends ChangeNotifier with EmojiStore, UserStore, Channel
       realmMandatoryTopics: initialSnapshot.realmMandatoryTopics,
       realmWaitingPeriodThreshold: initialSnapshot.realmWaitingPeriodThreshold,
       maxFileUploadSizeMib: initialSnapshot.maxFileUploadSizeMib,
+      realmEmptyTopicDisplayName: initialSnapshot.realmEmptyTopicDisplayName,
       realmDefaultExternalAccounts: initialSnapshot.realmDefaultExternalAccounts,
       customProfileFields: _sortCustomProfileFields(initialSnapshot.customProfileFields),
       emailAddressVisibility: initialSnapshot.emailAddressVisibility,
@@ -344,6 +345,7 @@ class PerAccountStore extends ChangeNotifier with EmojiStore, UserStore, Channel
     required this.realmMandatoryTopics,
     required this.realmWaitingPeriodThreshold,
     required this.maxFileUploadSizeMib,
+    required String? realmEmptyTopicDisplayName,
     required this.realmDefaultExternalAccounts,
     required this.customProfileFields,
     required this.emailAddressVisibility,
@@ -362,6 +364,7 @@ class PerAccountStore extends ChangeNotifier with EmojiStore, UserStore, Channel
        assert(realmUrl == connection.realmUrl),
        assert(emoji.realmUrl == realmUrl),
        _globalStore = globalStore,
+       _realmEmptyTopicDisplayName = realmEmptyTopicDisplayName,
        _emoji = emoji,
        _users = users,
        _channels = channels,
@@ -414,6 +417,11 @@ class PerAccountStore extends ChangeNotifier with EmojiStore, UserStore, Channel
   /// For docs, please see [InitialSnapshot.realmWaitingPeriodThreshold].
   final int realmWaitingPeriodThreshold;  // TODO(#668): update this realm setting
   final int maxFileUploadSizeMib; // No event for this.
+  String get realmEmptyTopicDisplayName {
+    assert(_realmEmptyTopicDisplayName != null); // TODO(log)
+    return _realmEmptyTopicDisplayName ?? 'general chat';
+  }
+  final String? _realmEmptyTopicDisplayName; // TODO(#668): update this realm setting
   final Map<String, RealmDefaultExternalAccount> realmDefaultExternalAccounts;
   List<CustomProfileField> customProfileFields;
   /// For docs, please see [InitialSnapshot.emailAddressVisibility].

lib/widgets/action_sheet.dart

@@ -249,7 +249,12 @@ void showTopicActionSheet(BuildContext context, {
       pageContext: pageContext);
   }));
 
-  if (someMessageIdInTopic != null) {
+  final message = store.messages[someMessageIdInTopic] as StreamMessage?;
+  // TODO: check for other cases that may disallow this action (e.g.: time
+  //   limit for editing topics).
+  final allowResolveUnresolve =
+    message == null || message.topic.displayName != null;
+  if (someMessageIdInTopic != null && allowResolveUnresolve) {
     optionButtons.add(ResolveUnresolveButton(pageContext: pageContext,
       topic: topic,
       someMessageIdInTopic: someMessageIdInTopic));
@@ -693,9 +698,12 @@ Future<String?> fetchRawContentWithFeedback({
     //   On final failure or success, auto-dismiss the snackbar.
     final zulipLocalizations = ZulipLocalizations.of(context);
     try {
-      fetchedMessage = await getMessageCompat(PerAccountStoreWidget.of(context).connection,
+      final store = PerAccountStoreWidget.of(context);
+      fetchedMessage = await getMessageCompat(store.connection,
         messageId: messageId,
         applyMarkdown: false,
+        // TODO(server-10): simplify this condition away
+        allowEmptyTopicName: store.zulipFeatureLevel >= 334 ? true : null,
       );
       if (fetchedMessage == null) {
         errorMessage = zulipLocalizations.errorMessageDoesNotSeemToExist;

lib/widgets/autocomplete.dart

@@ -367,12 +367,21 @@ class TopicAutocomplete extends AutocompleteField<TopicAutocompleteQuery, TopicA
 
   @override
   Widget buildItem(BuildContext context, int index, TopicAutocompleteResult option) {
+    final Widget child;
+    if (option.topic.displayName == null) {
+      final store = PerAccountStoreWidget.of(context);
+      child = Text(store.realmEmptyTopicDisplayName,
+        style: const TextStyle(fontStyle: FontStyle.italic));
+    } else {
+      child = Text(option.topic.displayName!);
+    }
+
     return InkWell(
       onTap: () {
         _onTapOption(context, option);
       },
       child: Padding(
         padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
-        child: Text(option.topic.displayName)));
+        child: child));
   }
 }