Question:

I am working with a FastAPI application where I am trying to handle a form submission with an optional file upload. However, I am encountering a 422 Unprocessable Entity error when sending a POST request to /submit_response.

Here’s the relevant code for the endpoint:

@app.post("/submit_response")
async def submit_response(
    session_id: str = Form(...),
    response_text: Optional[str] = Form(None),
    audio_file: Optional[UploadFile] = File(None)
):
    session = get_session(session_id)

    if audio_file:
        file_location = f"temp_{audio_file.filename}"
        with open(file_location, "wb") as f:
            f.write(audio_file.file.read())
        response_text = transcribe_audio_from_file(file_location)
        os.remove(file_location)
    
    if not response_text:
        raise HTTPException(status_code=400, detail="Response text or audio file is required")

    # Process response_text and update session
    # [Code continues...]

And here’s the transcriber code used to convert audio to text:

@app.post("/transcribe_audio")
async def transcribe_audio(file: UploadFile = File(...)):
    file_location = f"temp_{file.filename}"
    with open(file_location, "wb") as f:
        f.write(file.file.read())
    
    transcript = transcribe_audio_from_file(file_location)
    os.remove(file_location)
    
    return {"transcript": transcript}

def transcribe_audio_from_file(file_path):
    client = speech_v1.SpeechClient.from_service_account_json('convstt.json')

    # Read audio file
    with open(file_path, "rb") as audio_file:
        audio_content = audio_file.read()

    audio = types.RecognitionAudio(content=audio_content)
    config = types.RecognitionConfig(
        encoding=types.RecognitionConfig.AudioEncoding.LINEAR16,
        language_code='en-US'  # Replace with your language code if different
    )

    response = client.recognize(config=config, audio=audio)

    transcript = ""
    for result in response.results:
        transcript += result.alternatives[0].transcript

    return transcript

Problem:

When I send a POST request to /submit_response with session_id, response_text, and optionally an audio_file, I receive the following response:

INFO:__main__:Request: POST http://localhost:8000/submit_response
INFO:__main__:Response status: 422
INFO:     127.0.0.1:57679 - "POST /submit_response HTTP/1.1" 422 Unprocessable Entity

What I’ve Tried:

1. Check Request Data: Verified that the request includes all required fields and is properly formatted.
2. Update Endpoint: Added validation to ensure required fields are processed correctly.
3. Logs and Debugging: Checked the logs and request data, but could not identify the cause of the validation error.

Question:

What might be causing the 422 Unprocessable Entity error in this scenario, and how can I resolve it? Are there specific aspects of the request or FastAPI handling that might be causing the issue?

Additional Information:

• I am using FastAPI and Pydantic.
• The submit_response endpoint expects session_id, response_text, and optionally audio_file.
• The error occurs even when the request data appears to be correct.