Check if the conversation was cancelled on send methods

Fixes #1411.

telethon/tl/custom/conversation.py

@@ -1,4 +1,5 @@
 import asyncio
+import functools
 import itertools
 import time
 
@@ -11,6 +12,16 @@ from ... import helpers, utils, errors
 _EDIT_COLLISION_DELTA = 0.001
 
 
+def _checks_cancelled(f):
+    @functools.wraps(f)
+    def wrapper(self, *args, **kwargs):
+        if self._cancelled:
+            raise asyncio.CancelledError('The conversation was cancelled before')
+
+        return f(self, *args, **kwargs)
+    return wrapper
+
+
 class Conversation(ChatGetter):
     """
     Represents a conversation inside an specific chat.
@@ -66,6 +77,7 @@ class Conversation(ChatGetter):
 
         self._edit_dates = {}
 
+    @_checks_cancelled
     async def send_message(self, *args, **kwargs):
         """
         Sends a message in the context of this conversation. Shorthand
@@ -81,6 +93,7 @@ class Conversation(ChatGetter):
         self._last_outgoing = ms[-1].id
         return sent
 
+    @_checks_cancelled
     async def send_file(self, *args, **kwargs):
         """
         Sends a file in the context of this conversation. Shorthand
@@ -96,6 +109,7 @@ class Conversation(ChatGetter):
         self._last_outgoing = ms[-1].id
         return sent
 
+    @_checks_cancelled
     def mark_read(self, message=None):
         """
         Marks as read the latest received message if ``message is None``.
@@ -379,10 +393,8 @@ class Conversation(ChatGetter):
         else:
             raise ValueError('No message was sent previously')
 
+    @_checks_cancelled
     def _get_result(self, future, start_time, timeout, pending, target_id):
-        if self._cancelled:
-            raise asyncio.CancelledError('The conversation was cancelled before')
-
         due = self._total_due
         if timeout is None:
             timeout = self._timeout