Add a catch-all error handler using ProblemDetails

src/labthings_fastapi/server/__init__.py

@@ -33,6 +33,7 @@
 
 # `_thing_servers` is used as a global from `ThingServer.__init__`
 from labthings_fastapi.outputs import blob
+from labthings_fastapi.problem_details import ProblemDetails
 from labthings_fastapi.server.config_model import (
     ThingsConfig,
     ThingServerConfig,
@@ -245,6 +246,21 @@
     def _add_exception_handlers(self) -> None:
         """Add exception handlers to the FastAPI application."""
 
+        @self.app.exception_handler(Exception)
+        async def exceptions_to_problemdetails(
+            _request: Request, exc: Exception
+        ) -> JSONResponse:
+            """Handle all exceptions by returning a ProblemDetails object.
+
+            By default, this does not expose stack traces or line numbers.
+
+            :param _request: the request that started the code that failed.
+            :param exc: the error that occurred.
+            :return: a response containing a ProblemDetails object.
+            """
+            pd = ProblemDetails.from_exception(exc)
+            return JSONResponse(pd.model_dump(), status_code=pd.status or 500)
+
         @self.app.exception_handler(GlobalLockBusyError)
         async def global_lock_exception_handler(
             _request: Request, exc: GlobalLockBusyError
@@ -258,11 +274,11 @@
         async def serialisation_error_handler(
             request: Request, exc: PydanticSerializationError
         ) -> JSONResponse:
             LOGGER.error(
                 f"Couldn't serialise response to {request.url} because of error: \n"
                 f"{exc}"
             )
             return JSONResponse(status_code=500, content={"detail": str(exc)})
 
     @property
     def debug(self) -> bool:
@@ -318,7 +334,7 @@
 
         :return: all instances of ``cls`` that have been added to this server.
         """
         return [t for t in self.things.values() if isinstance(t, cls)]
 
     def thing_by_class(self, cls: type[ThingInstance]) -> ThingInstance:
         """Return the instance of ``cls`` attached to this server.
@@ -332,10 +348,10 @@
 
         :raise RuntimeError: if there is not exactly one matching Thing.
         """
         instances = self.things_by_class(cls)
         if len(instances) == 1:
             return instances[0]
         raise RuntimeError(
             f"There are {len(instances)} Things of class {cls}, expected 1."
         )