feat: add handler name to exceptions in handler validation. (#3575)

* fix: add handler name to exceptions in handler validation.



---------

Co-authored-by: Raphael Krupinski <3732079+rafalkrupinski@users.noreply.github.com>
Co-authored-by: Janek Nouvertné <provinzkraut@posteo.de>

litestar/handlers/http_handlers/base.py

@@ -574,7 +574,7 @@ def _validate_handler_function(self) -> None:
 
         if return_type.annotation is Empty:
             raise ImproperlyConfiguredException(
-                "A return value of a route handler function should be type annotated. "
+                f"A return value of a route handler function {self} should be type annotated. "
                 "If your function doesn't return a value, annotate it as returning 'None'."
             )
 

litestar/handlers/http_handlers/decorators.py

@@ -596,7 +596,9 @@ def _validate_handler_function(self) -> None:
             or is_class_and_subclass(return_annotation, File)
             or is_class_and_subclass(return_annotation, ASGIFileResponse)
         ):
-            raise ImproperlyConfiguredException("A response to a head request should not have a body")
+            raise ImproperlyConfiguredException(
+                f"{self}: Handlers for 'HEAD' requests must not return a value. Either return 'None' or a response type without a body."
+            )
 
 
 class patch(HTTPRouteHandler):

litestar/handlers/websocket_handlers/route_handler.py

@@ -85,17 +85,19 @@ def _validate_handler_function(self) -> None:
         super()._validate_handler_function()
 
         if not self.parsed_fn_signature.return_type.is_subclass_of(NoneType):
-            raise ImproperlyConfiguredException("Websocket handler functions should return 'None'")
+            raise ImproperlyConfiguredException(f"{self}: WebSocket handlers must return 'None'")
 
         if "socket" not in self.parsed_fn_signature.parameters:
-            raise ImproperlyConfiguredException("Websocket handlers must set a 'socket' kwarg")
+            raise ImproperlyConfiguredException(f"{self}: WebSocket handlers must define a 'socket' parameter")
 
         for param in ("request", "body", "data"):
             if param in self.parsed_fn_signature.parameters:
-                raise ImproperlyConfiguredException(f"The {param} kwarg is not supported with websocket handlers")
+                raise ImproperlyConfiguredException(
+                    f"{self}: The {param} kwarg is not supported with websocket handlers"
+                )
 
         if not is_async_callable(self.fn):
-            raise ImproperlyConfiguredException("Functions decorated with 'websocket' must be async functions")
+            raise ImproperlyConfiguredException(f"{self}: WebSocket handler functions must be asynchronous")
 
 
 websocket = WebsocketRouteHandler