Scheduler: make _scheduled_tasks private

Main concern is someone trying to cancel a task directly. The workaround
for the race condition relies on the task only being cancelled via
Scheduler.cancel_task(), particularly because it removes the task from
the dictionary. The done callback will not remove from the dictionary
if it sees the task has already been cancelled. So it's a bad idea to
cancel tasks directly...

1 files changed, 6 insertions, 6 deletions

diff --git a/bot/utils/scheduling.py b/bot/utils/scheduling.py
index 40d26249f..0d66952eb 100644
--- a/bot/utils/scheduling.py
+++ b/bot/utils/scheduling.py
@@ -17,7 +17,7 @@ class Scheduler(metaclass=CogABCMeta):
         # Keep track of the child cog's name so the logs are clear.
         self.cog_name = self.__class__.__name__
 
-        self.scheduled_tasks: Dict[str, asyncio.Task] = {}
+        self._scheduled_tasks: Dict[str, asyncio.Task] = {}
 
     @abstractmethod
     async def _scheduled_task(self, task_object: dict) -> None:
@@ -39,7 +39,7 @@ class Scheduler(metaclass=CogABCMeta):
         """
         log.trace(f"{self.cog_name}: scheduling task #{task_id}...")
 
-        if task_id in self.scheduled_tasks:
+        if task_id in self._scheduled_tasks:
             log.debug(
                 f"{self.cog_name}: did not schedule task #{task_id}; task was already scheduled."
             )
@@ -48,14 +48,14 @@ class Scheduler(metaclass=CogABCMeta):
         task = asyncio.create_task(self._scheduled_task(task_data))
         task.add_done_callback(partial(self._task_done_callback, task_id))
 
-        self.scheduled_tasks[task_id] = task
+        self._scheduled_tasks[task_id] = task
         log.debug(f"{self.cog_name}: scheduled task #{task_id} {id(task)}.")
 
     def cancel_task(self, task_id: str) -> None:
         """Un-schedules a task."""
         log.trace(f"{self.cog_name}: cancelling task #{task_id}...")
 
-        task = self.scheduled_tasks.get(task_id)
+        task = self._scheduled_tasks.get(task_id)
 
         if task is None:
             log.warning(f"{self.cog_name}: Failed to unschedule {task_id} (no task found).")
@@ -63,7 +63,7 @@ class Scheduler(metaclass=CogABCMeta):
 
         task.cancel()
         log.debug(f"{self.cog_name}: unscheduled task #{task_id} {id(task)}.")
-        del self.scheduled_tasks[task_id]
+        del self._scheduled_tasks[task_id]
 
     def _task_done_callback(self, task_id: str, task: asyncio.Task) -> None:
         """
@@ -79,7 +79,7 @@ class Scheduler(metaclass=CogABCMeta):
                 task.exception()
         else:
             # Check if it exists to avoid logging a warning.
-            if task_id in self.scheduled_tasks:
+            if task_id in self._scheduled_tasks:
                 # Only cancel if the task is not cancelled to avoid a race condition when a new
                 # task is scheduled using the same ID. Reminders do this when re-scheduling after
                 # editing.