Improve error handling when background services are not initialized

RELEASE_NOTES.md

@@ -72,6 +72,8 @@
 
 - The `actor.ChannelRegistry` is now type-aware.
 
+- The error messages when `BackgroundService` implementations don't call `super().__init__()` have been improved.
+
 ## Bug Fixes
 
 - 0W power requests are now not adjusted to exclusion bounds by the `PowerManager` and `PowerDistributor`, and are sent over to the microgrid API directly.

src/frequenz/sdk/actor/_background_service.py

@@ -90,6 +90,7 @@ def name(self) -> str:
         Returns:
             The name of this background service.
         """
+        self._assert_initialized()
         return self._name
 
     @property
@@ -107,6 +108,7 @@ def tasks(self) -> collections.abc.Set[asyncio.Task[Any]]:
         Returns:
             The set of running tasks spawned by this background service.
         """
+        self._assert_initialized()
         return self._tasks
 
     @property
@@ -118,6 +120,7 @@ def is_running(self) -> bool:
         Returns:
             Whether this background service is running.
         """
+        self._assert_initialized()
         return any(not task.done() for task in self._tasks)
 
     def cancel(self, msg: str | None = None) -> None:
@@ -126,6 +129,7 @@ def cancel(self, msg: str | None = None) -> None:
         Args:
             msg: The message to be passed to the tasks being cancelled.
         """
+        self._assert_initialized()
         for task in self._tasks:
             task.cancel(msg)
 
@@ -144,6 +148,7 @@ async def stop(self, msg: str | None = None) -> None:
 
         [//]: # (# noqa: DAR401 rest)
         """
+        self._assert_initialized()
         if not self._tasks:
             return
         self.cancel(msg)
@@ -166,6 +171,7 @@ async def __aenter__(self) -> Self:
         Returns:
             This background service.
         """
+        self._assert_initialized()
         self.start()
         return self
 
@@ -196,6 +202,7 @@ async def wait(self) -> None:
                 exception (`CancelError` is not considered an error and not returned in
                 the exception group).
         """
+        self._assert_initialized()
         # We need to account for tasks that were created between when we started
         # awaiting and we finished awaiting.
         while self._tasks:
@@ -251,3 +258,10 @@ def __str__(self) -> str:
             A string representation of this instance.
         """
         return f"{type(self).__name__}[{self._name}]"
+
+    def _assert_initialized(self) -> None:
+        """Assert this instance is initialized."""
+        assert hasattr(self, "_tasks"), (
+            f"{type(self).__name__} instance is not initialized. "
+            "Make sure to call `super().__init__()` in your __init__() method."
+        )