Infer basic json schema (#28)

* Infer basic json schema on primitive types

examples/example.py

@@ -15,7 +15,8 @@
 from greeter import greeter
 from virtual_object import counter
 from workflow import payment
+from pydantic_greeter import pydantic_greeter
 
 import restate
 
-app = restate.app(services=[greeter, counter, payment])
+app = restate.app(services=[greeter, counter, payment, pydantic_greeter])

examples/pydantic_greeter.py

@@ -0,0 +1,33 @@
+#
+#  Copyright (c) 2023-2024 - Restate Software, Inc., Restate GmbH
+#
+#  This file is part of the Restate SDK for Python,
+#  which is released under the MIT license.
+#
+#  You can find a copy of the license in file LICENSE in the root
+#  directory of this repository or package, or at
+#  https://github.com/restatedev/sdk-typescript/blob/main/LICENSE
+#
+"""greeter.py"""
+# pylint: disable=C0116
+# pylint: disable=W0613
+# pylint: disable=C0115
+# pylint: disable=R0903
+
+from pydantic import BaseModel
+from restate import Service, Context
+
+# models
+class GreetingRequest(BaseModel):
+    name: str
+
+class Greeting(BaseModel):
+    message: str
+
+# service
+
+pydantic_greeter = Service("pydantic_greeter")
+
+@pydantic_greeter.handler()
+async def greet(ctx: Context, req: GreetingRequest) -> Greeting:
+    return Greeting(message=f"Hello {req.name}!")

examples/requirements.txt

@@ -1,2 +1,3 @@
 hypercorn
-restate_sdk
+restate_sdk
+pydantic

python/restate/discovery.py

@@ -25,10 +25,11 @@
 import json
 import typing
 from enum import Enum
-from typing import Optional, Any, List
+from typing import Optional, Any, List, get_args, get_origin
 
 
 from restate.endpoint import Endpoint as RestateEndpoint
+from restate.handler import TypeHint
 
 class ProtocolMode(Enum):
     BIDI_STREAM = "BIDI_STREAM"
@@ -99,6 +100,49 @@ def default(self, o):
             return o.value
         return {key: value for key, value in o.__dict__.items() if value is not None}
 
+
+# pylint: disable=R0911
+def type_hint_to_json_schema(type_hint: Any) -> Any:
+    """
+    Convert a Python type hint to a JSON schema.
+
+    """
+    origin = get_origin(type_hint) or type_hint
+    args = get_args(type_hint)
+    if origin is str:
+        return {"type": "string"}
+    if origin is int:
+        return {"type": "integer"}
+    if origin is float:
+        return {"type": "number"}
+    if origin is bool:
+        return {"type": "boolean"}
+    if origin is list:
+        items = type_hint_to_json_schema(args[0] if args else Any)
+        return {"type": "array", "items": items}
+    if origin is dict:
+        return {
+            "type": "object"
+        }
+    if origin is None:
+        return {"type": "null"}
+    # Default to all valid schema
+    return True
+
+def json_schema_from_type_hint(type_hint: Optional[TypeHint[Any]]) -> Any:
+    """
+    Convert a type hint to a JSON schema.
+    """
+    if not type_hint:
+        return None
+    if not type_hint.annotation:
+        return None
+    if type_hint.is_pydantic:
+        return type_hint.annotation.model_json_schema(mode='serialization') # type: ignore
+    return type_hint_to_json_schema(type_hint.annotation)
+
+
+
 def compute_discovery_json(endpoint: RestateEndpoint,
                            version: int,
                            discovered_as: typing.Literal["bidi", "request_response"]) -> typing.Tuple[typing.Dict[str, str] ,str]:
@@ -113,13 +157,6 @@ def compute_discovery_json(endpoint: RestateEndpoint,
     headers = {"content-type": "application/vnd.restate.endpointmanifest.v1+json"}
     return (headers, json_str)
 
-def try_extract_json_schema(model: Any) -> typing.Optional[typing.Any]:
-    """
-    Try to extract the JSON schema from a schema object
-    """
-    if model:
-        return model.model_json_schema(mode='serialization')
-    return None
 
 def compute_discovery(endpoint: RestateEndpoint, discovered_as : typing.Literal["bidi", "request_response"]) -> Endpoint:
     """
@@ -139,11 +176,11 @@ def compute_discovery(endpoint: RestateEndpoint, discovered_as : typing.Literal[
             # input
             inp = InputPayload(required=False,
                                contentType=handler.handler_io.accept,
-                               jsonSchema=try_extract_json_schema(handler.handler_io.pydantic_input_model))
+                               jsonSchema=json_schema_from_type_hint(handler.handler_io.input_type))
             # output
             out = OutputPayload(setContentTypeIfEmpty=False,
                                 contentType=handler.handler_io.content_type,
-                                jsonSchema=try_extract_json_schema(handler.handler_io.pydantic_output_model))
+                                jsonSchema=json_schema_from_type_hint(handler.handler_io.output_type))
             # add the handler
             service_handlers.append(Handler(name=handler.name, ty=ty, input=inp, output=out))
 

python/restate/handler.py

@@ -24,6 +24,7 @@
 
 I = TypeVar('I')
 O = TypeVar('O')
+T = TypeVar('T')
 
 # we will use this symbol to store the handler in the function
 RESTATE_UNIQUE_HANDLER_SYMBOL = str(object())
@@ -42,7 +43,7 @@ class Dummy: # pylint: disable=too-few-public-methods
 
         return Dummy
 
-PYDANTIC_BASE_MODEL = try_import_pydantic_base_model()
+PydanticBaseModel = try_import_pydantic_base_model()
 
 @dataclass
 class ServiceTag:
@@ -52,6 +53,14 @@ class ServiceTag:
     kind: Literal["object", "service", "workflow"]
     name: str
 
+@dataclass
+class TypeHint(Generic[T]):
+    """
+    Represents a type hint.
+    """
+    annotation: Optional[T] = None
+    is_pydantic: bool = False
+
 @dataclass
 class HandlerIO(Generic[I, O]):
     """
@@ -65,38 +74,43 @@ class HandlerIO(Generic[I, O]):
     content_type: str
     input_serde: Serde[I]
     output_serde: Serde[O]
-    pydantic_input_model: Optional[I] = None
-    pydantic_output_model: Optional[O] = None
+    input_type: Optional[TypeHint[I]] = None
+    output_type: Optional[TypeHint[O]] = None
 
 def is_pydantic(annotation) -> bool:
     """
     Check if an object is a Pydantic model.
     """
     try:
-        return issubclass(annotation, PYDANTIC_BASE_MODEL)
+        return issubclass(annotation, PydanticBaseModel)
     except TypeError:
         # annotation is not a class or a type
         return False
 
 
-def infer_pydantic_io(handler_io: HandlerIO[I, O], signature: Signature):
+def extract_io_type_hints(handler_io: HandlerIO[I, O], signature: Signature):
     """
-    Augment handler_io with Pydantic models when these are provided.
+    Augment handler_io with additional information about the input and output types.
+
+    This function has a special check for Pydantic models when these are provided.
     This method will inspect the signature of an handler and will look for
     the input and the return types of a function, and will:
     * capture any Pydantic models (to be used later at discovery)
     * replace the default json serializer (is unchanged by a user) with a Pydantic serde
     """
-    # check if the handlers I/O is a PydanticBaseModel
     annotation = list(signature.parameters.values())[-1].annotation
+    handler_io.input_type = TypeHint(annotation=annotation, is_pydantic=False)
+
     if is_pydantic(annotation):
-        handler_io.pydantic_input_model = annotation
+        handler_io.input_type.is_pydantic = True
         if isinstance(handler_io.input_serde, JsonSerde): # type: ignore
             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.pydantic_output_model = annotation
+        handler_io.output_type.is_pydantic=True
         if isinstance(handler_io.output_serde, JsonSerde): # type: ignore
             handler_io.output_serde = PydanticJsonSerde(annotation)
 
@@ -136,7 +150,7 @@ def make_handler(service_tag: ServiceTag,
         raise ValueError("Handler must have at least one parameter")
 
     arity = len(signature.parameters)
-    infer_pydantic_io(handler_io, signature)
+    extract_io_type_hints(handler_io, signature)
 
     handler = Handler[I, O](service_tag,
                             handler_io,

requirements.txt

@@ -2,4 +2,5 @@ mypy
 pylint
 hypercorn
 maturin
-pytest
+pytest
+pydantic