Add before/after loop callbacks

disagreement/ext/tasks.py

@@ -18,6 +18,8 @@ class Task:
         delta: Optional[datetime.timedelta] = None,
         time_of_day: Optional[datetime.time] = None,
         on_error: Optional[Callable[[Exception], Awaitable[None]]] = None,
+        before_loop: Optional[Callable[[], Awaitable[None] | None]] = None,
+        after_loop: Optional[Callable[[], Awaitable[None] | None]] = None,
     ) -> None:
         self._coro = coro
         self._task: Optional[asyncio.Task[None]] = None
@@ -36,6 +38,8 @@ class Task:
         self._seconds = float(interval_seconds)
         self._time_of_day = time_of_day
         self._on_error = on_error
+        self._before_loop = before_loop
+        self._after_loop = after_loop
 
     def _seconds_until_time(self) -> float:
         assert self._time_of_day is not None
@@ -47,6 +51,9 @@ class Task:
 
     async def _run(self, *args: Any, **kwargs: Any) -> None:
         try:
+            if self._before_loop is not None:
+                await _maybe_call_no_args(self._before_loop)
+
             first = True
             while True:
                 if self._time_of_day is not None:
@@ -65,6 +72,9 @@ class Task:
                 first = False
         except asyncio.CancelledError:
             pass
+        finally:
+            if self._after_loop is not None:
+                await _maybe_call_no_args(self._after_loop)
 
     def start(self, *args: Any, **kwargs: Any) -> asyncio.Task[None]:
         if self._task is None or self._task.done():
@@ -89,6 +99,12 @@ async def _maybe_call(
         await result
 
 
+async def _maybe_call_no_args(func: Callable[[], Awaitable[None] | None]) -> None:
+    result = func()
+    if asyncio.iscoroutine(result):
+        await result
+
+
 class _Loop:
     def __init__(
         self,
@@ -110,6 +126,8 @@ class _Loop:
         self.on_error = on_error
         self._task: Optional[Task] = None
         self._owner: Any = None
+        self._before_loop: Optional[Callable[..., Awaitable[Any]]] = None
+        self._after_loop: Optional[Callable[..., Awaitable[Any]]] = None
 
     def __get__(self, obj: Any, objtype: Any) -> "_BoundLoop":
         return _BoundLoop(self, obj)
@@ -119,7 +137,33 @@ class _Loop:
             return self.func(*args, **kwargs)
         return self.func(self._owner, *args, **kwargs)
 
+    def before_loop(
+        self, func: Callable[..., Awaitable[Any]]
+    ) -> Callable[..., Awaitable[Any]]:
+        self._before_loop = func
+        return func
+
+    def after_loop(
+        self, func: Callable[..., Awaitable[Any]]
+    ) -> Callable[..., Awaitable[Any]]:
+        self._after_loop = func
+        return func
+
     def start(self, *args: Any, **kwargs: Any) -> asyncio.Task[None]:
+        def call_before() -> Awaitable[None] | None:
+            if self._before_loop is None:
+                return None
+            if self._owner is not None:
+                return self._before_loop(self._owner)
+            return self._before_loop()
+
+        def call_after() -> Awaitable[None] | None:
+            if self._after_loop is None:
+                return None
+            if self._owner is not None:
+                return self._after_loop(self._owner)
+            return self._after_loop()
+
         self._task = Task(
             self._coro,
             seconds=self.seconds,
@@ -128,6 +172,8 @@ class _Loop:
             delta=self.delta,
             time_of_day=self.time_of_day,
             on_error=self.on_error,
+            before_loop=call_before,
+            after_loop=call_after,
         )
         return self._task.start(*args, **kwargs)
 

docs/task_loop.md

@@ -35,6 +35,22 @@ async def worker():
     ...
 ```
 
+Run setup and teardown code using `before_loop` and `after_loop`:
+
+```python
+@tasks.loop(seconds=5.0)
+async def worker():
+    ...
+
+@worker.before_loop
+async def before_worker():
+    print("starting")
+
+@worker.after_loop
+async def after_worker():
+    print("stopped")
+```
+
 You can also schedule a task at a specific time of day:
 
 ```python

tests/test_modals.py

@@ -28,5 +28,5 @@ async def test_respond_modal(dummy_bot, interaction):
     await interaction.respond_modal(modal)
     dummy_bot._http.create_interaction_response.assert_called_once()
     payload = dummy_bot._http.create_interaction_response.call_args.kwargs["payload"]
-    assert payload["type"] == InteractionCallbackType.MODAL.value
+    assert payload.type == InteractionCallbackType.MODAL
-    assert payload["data"]["custom_id"] == "m1"
+    assert payload.data["custom_id"] == "m1"

tests/test_tasks_extension.py

@@ -58,3 +58,27 @@ async def test_loop_runs_and_stops() -> None:
     dummy.work.stop()  # pylint: disable=no-member
     assert dummy.count >= 2
     assert not dummy.work.running  # pylint: disable=no-member
+
+
+@pytest.mark.asyncio
+async def test_before_after_loop_callbacks() -> None:
+    events: list[str] = []
+
+    @tasks.loop(seconds=0.01)
+    async def ticker() -> None:
+        events.append("tick")
+
+    @ticker.before_loop
+    async def before() -> None:  # pragma: no cover - trivial callback
+        events.append("before")
+
+    @ticker.after_loop
+    async def after() -> None:  # pragma: no cover - trivial callback
+        events.append("after")
+
+    ticker.start()
+    await asyncio.sleep(0.03)
+    ticker.stop()
+    await asyncio.sleep(0.01)
+    assert events and events[0] == "before"
+    assert "after" in events