Merge pull request #250 from DiamondLightSource/tidying

Log shutdown exception for better output
Try to give clearer error for p4p Value creation failure
Log exceptions in all attribute callbacks

Author: GDYendell

src/fastcs/attributes.py

@@ -163,7 +163,14 @@ async def update(self, value: T) -> None:
         self._value = self._datatype.validate(value)
 
         if self._on_update_callbacks is not None:
-            await asyncio.gather(*[cb(self._value) for cb in self._on_update_callbacks])
+            try:
+                await asyncio.gather(
+                    *[cb(self._value) for cb in self._on_update_callbacks]
+                )
+            except Exception as e:
+                logger.opt(exception=e).error(
+                    "On update callback failed", attribute=self, value=value
+                )
 
     def add_on_update_callback(self, callback: AttrOnUpdateCallback[T]) -> None:
         """Add a callback to be called when the value of the attribute is updated
@@ -197,8 +204,8 @@ async def update_attribute():
             try:
                 self.log_event("Update attribute", topic=self)
                 await update_callback(self)
-            except Exception:
-                logger.opt(exception=True).error("Update loop failed", attribute=self)
+            except Exception as e:
+                logger.opt(exception=e).error("Update loop failed", attribute=self)
                 raise
 
         return update_attribute
@@ -246,10 +253,20 @@ async def put(self, setpoint: T, sync_setpoint: bool = False) -> None:
         """
         setpoint = self._datatype.validate(setpoint)
         if self._on_put_callback is not None:
-            await self._on_put_callback(self, setpoint)
+            try:
+                await self._on_put_callback(self, setpoint)
+            except Exception as e:
+                logger.opt(exception=e).error(
+                    "Put failed", attribute=self, setpoint=setpoint
+                )
 
         if sync_setpoint:
-            await self._call_sync_setpoint_callbacks(setpoint)
+            try:
+                await self._call_sync_setpoint_callbacks(setpoint)
+            except Exception as e:
+                logger.opt(exception=e).error(
+                    "Sync setpoint failed", attribute=self, setpoint=setpoint
+                )
 
     async def _call_sync_setpoint_callbacks(self, setpoint: T) -> None:
         if self._sync_setpoint_callbacks:

src/fastcs/control_system.py

@@ -139,8 +139,8 @@ async def block_forever():
             await asyncio.gather(*coros)
         except asyncio.CancelledError:
             pass
-        except Exception as e:
-            raise RuntimeError("Unhandled exception in serve") from e
+        except Exception:
+            logger.exception("Unhandled exception in serve")
         finally:
             logger.info("Shutting down FastCS")
             self._stop_scan_tasks()

src/fastcs/transport/epics/pva/pvi_tree.py

@@ -139,15 +139,18 @@ def make_p4p_value(self) -> Value:
         raw_value = self._make_p4p_raw_value()
         p4p_type = self._make_type_for_raw_value(raw_value)
 
-        return Value(
-            p4p_type,
-            {
-                **p4p_alarm_states(),
-                **p4p_timestamp_now(),
-                **display,
-                "value": raw_value,
-            },
-        )
+        try:
+            return Value(
+                p4p_type,
+                {
+                    **p4p_alarm_states(),
+                    **p4p_timestamp_now(),
+                    **display,
+                    "value": raw_value,
+                },
+            )
+        except KeyError as e:
+            raise ValueError(f"Failed to create p4p Value from {raw_value}") from e
 
     def make_provider(
         self,