A little FastDepends presentation

fastflask.py

from functools import wraps

from flask import Flask, request
from flask.scaffold import setupmethod
from fast_depends import inject
from fast_depends.library import CustomField
from pydantic import PositiveInt, ValidationError


class Body(CustomField):
    def use(self, **kwargs):
        return {
            **super().use(**kwargs),
            self.param_name: (request.json or {}).get(self.param_name)
        }


def catch_validation_error(handler):
    @wraps(handler)
    def catch_wrapper(*args, **kwargs):
        try:
            return handler(*args, **kwargs)
        except ValidationError as e:
            return e.json(), 400
    return catch_wrapper


class FastFlask(Flask):
    @setupmethod
    def route(self, rule: str, **options):
        def decorator(f):
            f = catch_validation_error(inject(f))
            endpoint = options.pop("endpoint", None)
            self.add_url_rule(rule, endpoint, f, **options)
            return f
        return decorator


app = FastFlask(__name__)


@app.post("/<name>")
def hello(
    name: str,
    user_id: PositiveInt = Body(),
):
    return {
        name: user_id
    }