request引数のgenericsで指定したTypeからmarshmallowスキーマを生成して設定するwsgi wrapper

app.py

import json
import inspect
from datetime import datetime
from dataclasses import dataclass, asdict
from typing import TypeVar, Generic, Optional, Callable, Dict, Any, Type, Iterable, Sequence
from typing_extensions import Protocol
import webob
import webtest
import marshmallow_dataclass
from marshmallow import Schema

T = TypeVar("T")


class Request(Generic[T], webob.Request):
    def __init__(self, environ, data: T, schema: Schema) -> None:
        super().__init__(environ)
        self._data = data
        self.schema = schema

    @property
    def data(self) -> T:
        return self._data

TypedApp = Callable[[Request[T]], Dict[str, Any]]

class WSGIWrap(Generic[T]):
    def __init__(self, app: TypedApp[T]) -> None:
        self._app = app
        self._type: Type[T] = inspect.getfullargspec(app).annotations["request"].__args__[0]
        self._schema = marshmallow_dataclass.class_schema(self._type)()

    def __call__(self, environ, start_response) -> Iterable[bytes]:
        j = json.load(environ["wsgi.input"])
        data = self._schema.load(j).data
        print(data)
        req = Request(environ, data, self._schema)
        result = self._app(req)
        start_response("200 OK", [('Content-type', 'application/json')])
        return [json.dumps(result).encode("utf-8")]


@dataclass
class Person:
    first_name: str
    last_name: str

def app(request: Request[Person]) -> dict:
    d = request.data
    if d is None:
        return dict()
    return asdict(d)

wsgi_app = WSGIWrap(app)
test_app = webtest.TestApp(wsgi_app)
res = test_app.post_json("/", params={"first_name": "Atsushi", "last_name": "Odagiri"})
print(res)