Add InvocationError for an error without traceback. Alog cancel at info.

Author: julianstirling

src/labthings_fastapi/actions/__init__.py

@@ -33,6 +33,7 @@
 from ..dependencies.invocation import (
     CancelHook,
     InvocationCancelledError,
+    InvocationError,
     invocation_logger,
 )
 from ..outputs.blob import BlobIOContextDep, blobdata_to_url_ctx
@@ -280,10 +281,16 @@ def run(self) -> None:
                 self._status = InvocationStatus.COMPLETED
                 self.action.emit_changed_event(self.thing, self._status)
         except InvocationCancelledError:
-            logger.error(f"Invocation {self.id} was cancelled.")
+            logger.info(f"Invocation {self.id} was cancelled.")
             with self._status_lock:
                 self._status = InvocationStatus.CANCELLED
                 self.action.emit_changed_event(self.thing, self._status)
+        except InvocationError as e:
+            logger.error(e)
+            with self._status_lock:
+                self._status = InvocationStatus.ERROR
+                self._exception = e
+                self.action.emit_changed_event(self.thing, self._status)
         except Exception as e:  # skipcq: PYL-W0703
             logger.exception(e)
             with self._status_lock:

src/labthings_fastapi/dependencies/invocation.py

@@ -117,6 +117,20 @@ class InvocationCancelledError(BaseException):
     """
 
 
+class InvocationError(RuntimeError):
+    """The invocation ended in an anticipated error state.
+
+    When this error is raised, action execution stops as expected. The exception will be
+    logged at error level without a traceback, and the invocation will return with
+    error status.
+
+    Unlike other types of unhandled error in a LabThings action this will not cause
+    ASGI traceback. The ASGI traceback provides useful debug information to be logged
+    for developers. However, for simple errors with known causes this is information
+    overload for an average user.
+    """
+
+
 class CancelEvent(threading.Event):
     """An Event subclass that enables cancellation of actions.
 

src/labthings_fastapi/exceptions.py

@@ -1,6 +1,6 @@
 """A submodule for custom LabThings-FastAPI Exceptions."""
 
-from .dependencies.invocation import InvocationCancelledError
+from .dependencies.invocation import InvocationCancelledError, InvocationError
 
 
 class NotConnectedToServerError(RuntimeError):
@@ -13,4 +13,4 @@ class NotConnectedToServerError(RuntimeError):
     """
 
 
-__all__ = ["NotConnectedToServerError", "InvocationCancelledError"]
+__all__ = ["NotConnectedToServerError", "InvocationCancelledError", "InvocationError"]