Request with Forms and Files requires the 'File' parameter to be listed first

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn’t find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google “How to X in FastAPI” and didn’t find any information.
• I already read and followed all the tutorial in the docs and didn’t find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
• I already checked if it is not related to FastAPI but to Swagger UI.
• I already checked if it is not related to FastAPI but to ReDoc.

Commit to Help

• I commit to help with one of those options 👆

Example Code

@app.post( '/test-fail')
def test( param1: str = Form(...),	# It fails if the File goes first
          file: bytes = File(...)
        ):
    return Response(content=file, media_type="application/octet-stream")

@app.post( '/test-success')
def test( file: bytes = File(...),	# It succeeds if the File goes first 
          param1: str = Form(...)
        ):
    return Response(content=file, media_type="application/octet-stream")

Description

BUG The File parameter on the POST method must go first, before other Form parameters. Otherwise the end-point returns HTTP code 422.

Details A command line like below for the end-points from the example

curl --location --request POST 'http://127.0.0.1:5001/test' --form 'param1="fff"' --form 'file=@"file.png"'

would return HTTP code 200 with an expected result for /test-success and HTTP code 422 for /test-fail with the following JSON:

{"detail":[{"loc":["body","file"],"msg":"byte type expected","type":"type_error.bytes"}]}

Expected behaviour Validation of parameters doesn’t depend on the order of the parameters

Operating System

macOS

Operating System Details

v12.0.1

FastAPI Version

0.70.1

Python Version

3.7.10

Additional Context

No response

[AKlaus]

Closing as a duplicate of #1964.

Thank you @harunyasar for pointing out to that ticket! (I question my searching skills)

[harunyasar]

Apparently, I am mistaken.

https://github.com/tiangolo/fastapi/issues/1964