Bug: [OpenAPI] Upload file is not possible when defined as Optional

[vkuznetsovgn]

Description

When defining an UploadFile as Optional the upload file button disappears.
Removing the Optional makes the button to be present but there's no way not to specify the file anymore as there's no send empty value checkbox in this case.

MCVE

from typing import Annotated, Optional
from pydantic import BaseModel, ConfigDict
from litestar.datastructures import UploadFile
from litestar.enums import RequestEncodingType
from litestar.params import Body

class FormData(BaseModel):
    model_config = ConfigDict(arbitrary_types_allowed=True)
    
    file: Optional[UploadFile]
    some_params: dict


@post("/test")
async def handle_file(data: Annotated[FormData, Body(media_type=RequestEncodingType.MULTI_PART)]) -> None:
    print(data.file)


app = Litestar(route_handlers=[handle_file])

Litestar Version

2.8.2

Platform

• Linux
• Mac
• Windows
• Other (Please specify in the description above)

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[peterschutt]

I believe a dup of this: #3411

[vkuznetsovgn]

@peterschutt Possibly but I'm not sure as the OpenAPI UI looks differently in your case. Maybe we could merge two issues. In my case, there's also no send empty value checkmark available without the Optional.