Debug exception do not inherit from BaseException error

Author: ela-kotulska-frequenz

src/frequenz/sdk/timeseries/formula_engine/_formula_evaluator.py

@@ -94,7 +94,11 @@ async def stop(self) -> None:
             asyncio.create_task(cancel_and_await(task))
             for task in self._pending_fetch_tasks
         ]
+        # Here fetch_next task should receive CancelError. But instead
+        # receiver returns error that do not inherit from BaseException.
+        print("!!! HERE DEBUG: Stopping fetch tasks")
         await asyncio.wait(tasks_to_cancel, return_when=asyncio.ALL_COMPLETED)
+        print("!! HERE DEBUG: Stopped fetch tasks")
         self._pending_fetch_tasks = []
 
     async def apply(self) -> Sample[QuantityT]:

src/frequenz/sdk/timeseries/formula_engine/_formula_steps.py

@@ -529,7 +529,15 @@ async def _fetch_next(self) -> Sample[QuantityT] | None:
         try:
             next_value = await self._stream.receive()
         except ReceiverError[Any] as err:
-            _logger.error("Failed to fetch next value from %s: %s", self._name, err)
+            # I tried to catch
+            # 1. BaseException - it showed that an error is here, but error was empty
+            # 2. Exception - then nothings happen, everything works and this log is not printed
+            _logger.error(
+                "Failed to fetch next value from %s: %s, END", self._name, err
+            )
+            # Return because otherwise we start fallback formula.
+            # This should be improved removed after we know what is wrong with this exception
+            return
         else:
             if self._is_value_valid(next_value.value):
                 return next_value