allow Loop.change_interval to be called in before_loop and after_loop (#661)

Author: Makiyu-py

discord/ext/tasks/__init__.py

@@ -121,6 +121,8 @@ def __init__(
 
         self._before_loop = None
         self._after_loop = None
+        self._before_loop_running = False
+        self._after_loop_running = False
         self._is_being_cancelled = False
         self._has_failed = False
         self._stop_next_iteration = False
@@ -141,11 +143,17 @@ async def _call_loop_function(self, name: str, *args: Any, **kwargs: Any) -> Non
         if coro is None:
             return
 
+        if name.endswith('_loop'):
+            setattr(self, f'_{name}_running', True)
+
         if self._injected is not None:
             await coro(self._injected, *args, **kwargs)
         else:
             await coro(*args, **kwargs)
 
+        if name.endswith('_loop'):
+            setattr(self, f'_{name}_running', False)
+
     def _try_sleep_until(self, dt: datetime.datetime):
         self._handle = SleepHandle(dt=dt, loop=self.loop)
         return self._handle.wait()
@@ -680,7 +688,7 @@ def change_interval(
             self._time = self._get_time_parameter(time)
             self._sleep = self._seconds = self._minutes = self._hours = MISSING
 
-        if self.is_running():
+        if self.is_running() and not (self._before_loop_running or self._after_loop_running):
             if self._time is not MISSING:
                 # prepare the next time index starting from after the last iteration
                 self._prepare_time_index(now=self._last_iteration)