Fix discovery information for void args

Author: igalshilman

python/restate/discovery.py

@@ -54,13 +54,13 @@ def __init__(self, required: bool, contentType: str, jsonSchema: Optional[Any] =
         self.jsonSchema = jsonSchema
 
 class OutputPayload:
-    def __init__(self, contentType: str, setContentTypeIfEmpty: bool, jsonSchema: Optional[Any] = None):
+    def __init__(self, setContentTypeIfEmpty: bool, contentType: Optional[str] = None, jsonSchema: Optional[Any] = None):
         self.contentType = contentType
         self.setContentTypeIfEmpty = setContentTypeIfEmpty
         self.jsonSchema = jsonSchema
 
 class Handler:
-    def __init__(self, name: str, ty: Optional[ServiceHandlerType] = None, input: Optional[InputPayload] = None, output: Optional[OutputPayload] = None, description: Optional[str] = None, metadata: Optional[Dict[str, str]] = None):
+    def __init__(self, name: str, ty: Optional[ServiceHandlerType] = None, input: Optional[InputPayload | Dict[str, str]] = None, output: Optional[OutputPayload] = None, description: Optional[str] = None, metadata: Optional[Dict[str, str]] = None):
         self.name = name
         self.ty = ty
         self.input = input
@@ -180,13 +180,20 @@ def compute_discovery(endpoint: RestateEndpoint, discovered_as : typing.Literal[
             else:
                 ty = None
             # input
-            inp = InputPayload(required=False,
-                               contentType=handler.handler_io.accept,
-                               jsonSchema=json_schema_from_type_hint(handler.handler_io.input_type))
+            inp: Optional[InputPayload | Dict[str, str]] = None
+            if handler.handler_io.input_type and handler.handler_io.input_type.is_void:
+                inp = {}
+            else:
+                inp =InputPayload(required=False,
+                                   contentType=handler.handler_io.accept,
+                                   jsonSchema=json_schema_from_type_hint(handler.handler_io.input_type))
             # output
-            out = OutputPayload(setContentTypeIfEmpty=False,
-                                contentType=handler.handler_io.content_type,
-                                jsonSchema=json_schema_from_type_hint(handler.handler_io.output_type))
+            if handler.handler_io.output_type and handler.handler_io.output_type.is_void:
+                out = OutputPayload(setContentTypeIfEmpty=False)
+            else:
+                out = OutputPayload(setContentTypeIfEmpty=False,
+                                    contentType=handler.handler_io.content_type,
+                                    jsonSchema=json_schema_from_type_hint(handler.handler_io.output_type))
             # add the handler
             service_handlers.append(Handler(name=handler.name,
                                             ty=ty,

python/restate/handler.py

@@ -46,6 +46,7 @@ class TypeHint(Generic[T]):
     """
     annotation: Optional[T] = None
     is_pydantic: bool = False
+    is_void: bool = False
 
 @dataclass
 class HandlerIO(Generic[I, O]):
@@ -74,21 +75,28 @@ def update_handler_io_with_type_hints(handler_io: HandlerIO[I, O], signature: Si
     * capture any Pydantic models (to be used later at discovery)
     * replace the default json serializer (is unchanged by a user) with a Pydantic serde
     """
-    annotation = list(signature.parameters.values())[-1].annotation
-    handler_io.input_type = TypeHint(annotation=annotation, is_pydantic=False)
-
-    if is_pydantic(annotation):
-        handler_io.input_type.is_pydantic = True
-        if isinstance(handler_io.input_serde, DefaultSerde):
-            handler_io.input_serde = PydanticJsonSerde(annotation)
+    params = list(signature.parameters.values())
+    if len(params) == 1:
+        # if there is only one parameter, it is the context.
+        handler_io.input_type = TypeHint(is_void=True)
+    else:
+        annotation = params[-1].annotation
+        handler_io.input_type = TypeHint(annotation=annotation, is_pydantic=False)
+        if is_pydantic(annotation):
+            handler_io.input_type.is_pydantic = True
+            if isinstance(handler_io.input_serde, DefaultSerde):
+                handler_io.input_serde = PydanticJsonSerde(annotation)
 
     annotation = signature.return_annotation
-    handler_io.output_type = TypeHint(annotation=annotation, is_pydantic=False)
-
-    if is_pydantic(annotation):
-        handler_io.output_type.is_pydantic=True
-        if isinstance(handler_io.output_serde, DefaultSerde):
-            handler_io.output_serde = PydanticJsonSerde(annotation)
+    if annotation is None or annotation is Signature.empty:
+        # if there is no return annotation, we assume it is void
+        handler_io.output_type = TypeHint(is_void=True)
+    else:
+        handler_io.output_type = TypeHint(annotation=annotation, is_pydantic=False)
+        if is_pydantic(annotation):
+            handler_io.output_type.is_pydantic=True
+            if isinstance(handler_io.output_serde, DefaultSerde):
+                handler_io.output_serde = PydanticJsonSerde(annotation)
 
 # pylint: disable=R0902
 @dataclass