Reduce __enter__/__exit__ boilerplate for sync ctx managers

telethon/helpers.py

@@ -102,6 +102,25 @@ async def _cancel(log, **tasks):
         except Exception:
             log.exception('Unhandled exception from %s after cancel', name)
 
+
+def _sync_enter(self):
+    """
+    Helps to cut boilerplate on async context
+    managers that offer synchronous variants.
+    """
+    if self._client.loop.is_running():
+        raise RuntimeError(
+            'You must use "async with" if the event loop '
+            'is running (i.e. you are inside an "async def")'
+        )
+
+    return self._client.loop.run_until_complete(self.__aenter__())
+
+
+def _sync_exit(self, *args):
+    return self._client.loop.run_until_complete(self.__aexit__(*args))
+
+
 # endregion
 
 # region Cryptographic related utils