Allow to change topic name and icon separately.

td/generate/scheme/td_api.tl

@@ -5324,9 +5324,10 @@ createForumTopic chat_id:int53 name:string icon:forumTopicIcon = ForumTopicInfo;
 //@description Edits title and icon of a topic in a forum supergroup chat; requires can_manage_topics administrator rights in the supergroup unless the user is creator of the topic
 //@chat_id Identifier of the chat
 //@message_thread_id Message thread identifier of the forum topic
-//@name New name of the topic; 1-128 characters
+//@name New name of the topic; 0-128 characters. If empty, the previous topic name is kept
-//@icon_custom_emoji_id Identifier of the new custom emoji for topic icon. Telegram Premium users can use any custom emoji, other users can use only a custom emoji returned by getForumTopicDefaultIcons
+//@edit_icon_custom_emoji Pass true to edit the icon of the topic
-editForumTopic chat_id:int53 message_thread_id:int53 name:string icon_custom_emoji_id:int64 = Ok;
+//@icon_custom_emoji_id Identifier of the new custom emoji for topic icon; pass 0 to remove the custom emoji. Ignored if edit_icon_custom_emoji is false. Telegram Premium users can use any custom emoji, other users can use only a custom emoji returned by getForumTopicDefaultIcons
+editForumTopic chat_id:int53 message_thread_id:int53 name:string edit_icon_custom_emoji:Bool icon_custom_emoji_id:int64 = Ok;
 
 //@description Toggles whether a topic is closed in a forum supergroup chat; requires can_manage_topics administrator rights in the supergroup unless the user is creator of the topic
 //@chat_id Identifier of the chat

td/telegram/ForumTopicManager.cpp

@@ -121,16 +121,21 @@ class EditForumTopicQuery final : public Td::ResultHandler {
   explicit EditForumTopicQuery(Promise<Unit> &&promise) : promise_(std::move(promise)) {
   }
 
-  void send(ChannelId channel_id, MessageId top_thread_message_id, const string &title,
+  void send(ChannelId channel_id, MessageId top_thread_message_id, bool edit_title, const string &title,
-            CustomEmojiId icon_custom_emoji_id) {
+            bool edit_custom_emoji_id, CustomEmojiId icon_custom_emoji_id) {
     channel_id_ = channel_id;
     top_thread_message_id_ = top_thread_message_id;
 
     auto input_channel = td_->contacts_manager_->get_input_channel(channel_id);
     CHECK(input_channel != nullptr);
 
-    int32 flags =
+    int32 flags = 0;
-        telegram_api::channels_editForumTopic::TITLE_MASK | telegram_api::channels_editForumTopic::ICON_EMOJI_ID_MASK;
+    if (edit_title) {
+      flags |= telegram_api::channels_editForumTopic::TITLE_MASK;
+    }
+    if (edit_custom_emoji_id) {
+      flags |= telegram_api::channels_editForumTopic::ICON_EMOJI_ID_MASK;
+    }
     send_query(G()->net_query_creator().create(
         telegram_api::channels_editForumTopic(flags, std::move(input_channel),
                                               top_thread_message_id.get_server_message_id().get(), title,
@@ -257,7 +262,8 @@ void ForumTopicManager::on_forum_topic_created(DialogId dialog_id, unique_ptr<Fo
 }
 
 void ForumTopicManager::edit_forum_topic(DialogId dialog_id, MessageId top_thread_message_id, string &&title,
-                                         CustomEmojiId icon_custom_emoji_id, Promise<Unit> &&promise) {
+                                         bool edit_icon_custom_emoji, CustomEmojiId icon_custom_emoji_id,
+                                         Promise<Unit> &&promise) {
   TRY_STATUS_PROMISE(promise, is_forum(dialog_id));
   auto channel_id = dialog_id.get_channel_id();
 
@@ -272,13 +278,14 @@ void ForumTopicManager::edit_forum_topic(DialogId dialog_id, MessageId top_threa
     }
   }
 
+  bool edit_title = !title.empty();
   auto new_title = clean_name(std::move(title), MAX_FORUM_TOPIC_TITLE_LENGTH);
-  if (new_title.empty()) {
+  if (edit_title && new_title.empty()) {
     return promise.set_error(Status::Error(400, "Title must be non-empty"));
   }
 
   td_->create_handler<EditForumTopicQuery>(std::move(promise))
-      ->send(channel_id, top_thread_message_id, new_title, icon_custom_emoji_id);
+      ->send(channel_id, top_thread_message_id, edit_title, new_title, edit_icon_custom_emoji, icon_custom_emoji_id);
 }
 
 void ForumTopicManager::toggle_forum_topic_is_closed(DialogId dialog_id, MessageId top_thread_message_id,

td/telegram/ForumTopicManager.h

@@ -41,7 +41,7 @@ class ForumTopicManager final : public Actor {
                               Promise<td_api::object_ptr<td_api::forumTopicInfo>> &&promise);
 
   void edit_forum_topic(DialogId dialog_id, MessageId top_thread_message_id, string &&title,
-                        CustomEmojiId icon_custom_emoji_id, Promise<Unit> &&promise);
+                        bool edit_icon_custom_emoji, CustomEmojiId icon_custom_emoji_id, Promise<Unit> &&promise);
 
   void toggle_forum_topic_is_closed(DialogId dialog_id, MessageId top_thread_message_id, bool is_closed,
                                     Promise<Unit> &&promise);

td/telegram/Td.cpp

@@ -5545,8 +5545,8 @@ void Td::on_request(uint64 id, td_api::editForumTopic &request) {
   CLEAN_INPUT_STRING(request.name_);
   CREATE_OK_REQUEST_PROMISE();
   forum_topic_manager_->edit_forum_topic(DialogId(request.chat_id_), MessageId(request.message_thread_id_),
-                                         std::move(request.name_), CustomEmojiId(request.icon_custom_emoji_id_),
+                                         std::move(request.name_), request.edit_icon_custom_emoji_,
-                                         std::move(promise));
+                                         CustomEmojiId(request.icon_custom_emoji_id_), std::move(promise));
 }
 
 void Td::on_request(uint64 id, const td_api::toggleForumTopicIsClosed &request) {

td/telegram/cli.cpp

@@ -3873,9 +3873,11 @@ class CliClient final : public Actor {
       ChatId chat_id;
       MessageThreadId message_thread_id;
       string name;
+      bool edit_icon_custom_emoji;
       int64 icon_custom_emoji_id;
-      get_args(args, chat_id, message_thread_id, name, icon_custom_emoji_id);
+      get_args(args, chat_id, message_thread_id, name, edit_icon_custom_emoji, icon_custom_emoji_id);
-      send_request(td_api::make_object<td_api::editForumTopic>(chat_id, message_thread_id, name, icon_custom_emoji_id));
+      send_request(td_api::make_object<td_api::editForumTopic>(chat_id, message_thread_id, name, edit_icon_custom_emoji,
+                                                               icon_custom_emoji_id));
     } else if (op == "tftic") {
       ChatId chat_id;
       MessageThreadId message_thread_id;