Response Schema, Fastapi Streaming Responses for Documentation

[anantgupta129]

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Example Code

from fastapi import FastAPI, HTTPException
from fastapi.responses import StreamingResponse
from pydantic import BaseModel

import json
import time
import asyncio

app = FastAPI()

class ErrorModel(BaseModel):
    detail: str

def fake_json_streamer():
    t0 = time.time()
    for i in range(10):
        print(f"Chunk being yielded (time {int((time.time()-t0)*1000)}ms)", flush=True)
        yield json.dumps( {"message": "Hello World"}) + '\n'
        time.sleep(0.5)
    print(f"Over (time {int((time.time()-t0)*1000)}ms)", flush=True)


@app.get("/test", responses={500: {"model": ErrorModel}})
async def test():
    try:
        return StreamingResponse(fake_json_streamer(), media_type='text/event-stream')
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"An error occurred while processing the request. {str(e)}")

Description

How to add schema for documentation to return streaming responses for text or json

Operating System

Windows

Operating System Details

No response

FastAPI Version

0.109.2

Pydantic Version

2.6.1

Python Version

3.9.19

Additional Context

No response

[n8sty]

See the additional responses section of the docs https://fastapi.tiangolo.com/advanced/additional-responses/

[anantgupta129]

but it does not cover any model for streaming response, how can i add response model for streaming responses so that its correctly displayed in the swagger/ redoc documentation

[YuriiMotov]

Could you give any examples or references to the openapi specification on what you want to achieve?

[anantgupta129]

hi i want to have clearer documentation, when accesing /docs or /redoc, what is the best to mention that the request is a streaming response

[YuriiMotov]

Hi!

If you are talking about clarifications for people who read docs, then you can add the description for 200 response:

@app.get("/test", responses={200: {"description": "Successfull response will return a stream of JSON objects"}, 500: {"model": ErrorModel}})

And if you are talking about specifying response type for client code generators, it requires more investigation..
Have you read discussions below?
OAI/OpenAPI-Specification#1576
OAI/OpenAPI-Specification#3730
OAI/OpenAPI-Specification#3769