Add filters.FORUM (#4906)

changes/unreleased/4906.Fju7LDJgwCz2sxgQy9muBG.toml

@@ -0,0 +1,5 @@
+features = "Add ``filters.FORUM`` to filter messages from forum topic chats"
+[[pull_requests]]
+uid = "4906"
+author_uid = "harshil21"
+closes_threads = []

src/telegram/ext/filters.py

@@ -50,6 +50,7 @@ __all__ = (
     "COMMAND",
     "CONTACT",
     "EFFECT_ID",
+    "FORUM",
     "FORWARDED",
     "GAME",
     "GIVEAWAY",
@@ -1366,6 +1367,20 @@ class Entity(MessageFilter):
         return any(entity.type == self.entity_type for entity in message.entities)
 
 
+class _Forum(UpdateFilter):
+    __slots__ = ()
+
+    def filter(self, update: Update) -> bool:
+        return bool(update.effective_chat and update.effective_chat.is_forum)
+
+
+FORUM = _Forum(name="filters.FORUM")
+"""Messages that are from a forum (topics enabled) chat.
+
+.. versionadded:: NEXT.VERSION
+"""
+
+
 class _Forwarded(MessageFilter):
     __slots__ = ()
 

tests/ext/test_filters.py

@@ -1496,6 +1496,11 @@ class TestFilters:
         with pytest.raises(RuntimeError, match="Cannot set name"):
             f.name = "foo"
 
+    def test_filters_forum(self, update):
+        assert not filters.FORUM.check_update(update)
+        update.message.chat.is_forum = True
+        assert filters.FORUM.check_update(update)
+
     def test_filters_forwarded_from_init(self):
         with pytest.raises(RuntimeError, match="in conjunction with"):
             filters.ForwardedFrom(chat_id=1, username="chat")