FastAPI error when handling file together with form-data defined in a Pydantic model

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For some reason handling Form Data and File Upload at the same time raises an error.
Form
File
from typing import Annotated
from typing import Annotated
from pydantic import BaseModel, StringConstraints, EmailStr
from pydantic import BaseModel, StringConstraints, EmailStr
class RouteBody(BaseModel):
email: Annotated[EmailStr, StringConstraints(
max_length = 255
)]
password: Annotated[str, StringConstraints(
max_length = 60
)]

class RouteBody(BaseModel):
email: Annotated[EmailStr, StringConstraints(
max_length = 255
)]
password: Annotated[str, StringConstraints(
max_length = 60
)]

And this enforces that the routes body is correct. Super nice.
from fastapi import UploadFile, File
from fastapi import UploadFile, File
async def handleRoute(routeBody: RouteBody = Form(), profilePicture: UploadFile = File(...)):
return {"msg": "Route"}

async def handleRoute(routeBody: RouteBody = Form(), profilePicture: UploadFile = File(...)):
return {"msg": "Route"}

And I test it out using SwaggerUI docs:

I get the following error:
error [{'type': 'model_attributes_type', 'loc': ('body', 'routeBody'), 'msg': 'Input should be a valid dictionary or object to extract fields from', 'input': '{"email":"[email protected]","password":"string"}'}]
error [{'type': 'model_attributes_type', 'loc': ('body', 'routeBody'), 'msg': 'Input should be a valid dictionary or object to extract fields from', 'input': '{"email":"[email protected]","password":"string"}'}]
[email protected]

Tested it out on a separate route without the "RouteBody" and it worked perfectly.
Rewrote Route Handler from Scratch
Changed the order of the parameters (don't know why I thought this mattered ... maybe it did?)
Instead of using a Pydantic Model type for the RouteBody, I opted for individual parameters to make it functional. However, this isn’t an ideal solution, as it requires listing out all the parameters if you have many of them.
Asked ChatGPT for guidance

Tested it out on a separate route without the "RouteBody" and it worked perfectly.
Rewrote Route Handler from Scratch
Changed the order of the parameters (don't know why I thought this mattered ... maybe it did?)
Instead of using a Pydantic Model type for the RouteBody, I opted for individual parameters to make it functional. However, this isn’t an ideal solution, as it requires listing out all the parameters if you have many of them.
Asked ChatGPT for guidance

Tags: python,swagger,fastapi,multipartform-data,openapiSource of the question:

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