More fixes for suggestions:

- I forgot some places with func call
- More suitable docs for filter
- `if` in full block

telethon/events/callbackquery.py

@@ -118,8 +118,10 @@ class CallbackQuery(EventBuilder):
             elif event.query.data != self.match:
                 return
 
-        if not self.func or self.func(event):
-            return event
+        if self.func:
+            # Return the result of func directly as it may need to be awaited
+            return self.func(event)
+        return True
 
     class Event(EventCommon, SenderGetter):
         """

telethon/events/common.py

@@ -105,9 +105,8 @@ class EventBuilder(abc.ABC):
 
     def filter(self, event):
         """
-        If the ID of ``event._chat_peer`` isn't in the chats set (or it is
-        but the set is a blacklist) returns `True`, otherwise `False`.
-        May also return awaitable which awaits to bool-able value.
+        Returns a truthy value if the event passed the filter and should be
+        used, or falsy otherwise. The return value may need to be awaited.
 
         The events must have been resolved before this can be called.
         """

telethon/events/raw.py

@@ -46,6 +46,8 @@ class Raw(EventBuilder):
         return update
 
     def filter(self, event):
-        if ((not self.types or isinstance(event, self.types))
-                and (not self.func or self.func(event))):
+        if not self.types or isinstance(event, self.types):
+            if self.func:
+                # Return the result of func directly as it may need to be awaited
+                return self.func(event)
             return event

telethon/tl/custom/conversation.py

@@ -316,7 +316,9 @@ class Conversation(ChatGetter):
 
             if inst:
                 filter = ev.filter(inst)
-                filter = (await filter) if inspect.isawaitable(filter) else filter
+                if inspect.isawaitable(filter):
+                    filter = await filter
+
                 if filter:
                     fut.set_result(inst)
                     del self._custom[key]