recover response_model from output annotations

[AM-I-Human]

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

from fastapi import FastAPI

app = FastAPI()


@router.post("/have_output_example_and_schema", response_model=list)
async def test(input: int-> list:
    return []


@router.post("/have_not_output_example_and_schema")
async def test_2(input: int-> list:
    return []

Description

I think it will be nice if the type in response_model (in the app decorators) will be infered from the output annotation of the function.
By doing so you can avoid some documentation-code inconsistency.

Wanted Solution

When response_model is None it will try to use the annotation one, es by using self.response_model= response_model or get_output_annotation(fn)

@router.post("/have_not_output_example_and_schema")
async def test_2(input: int-> list:
    return []

Will be the same as

@router.post("/have_not_output_example_and_schema",response_model=list)
async def test_2(input: int-> list:
    return []

Wanted Code

from fastapi import FastAPI

app = FastAPI()


@router.post("/have_output_example_and_schema")
async def test(input: int-> list:
    return []


@router.post("/have_not_output_example_and_schema")
async def test_2(input: int-> list:
    return []

Alternatives

No response

Operating System

Windows

Operating System Details

Windows 11

FastAPI Version

0.75.0

Python Version

Python 3.10.4

Additional Context

No response

[chbndrhnns]

This has been discarded earlier, like in #101

[AM-I-Human]

Ah! I missed that, thanks.

[tiangolo]

Thanks for the help here @chbndrhnns! 👏 🙇

Thanks for reporting back and closing the issue @AM-I-Human 👍

This is now supported (optionally) in the latest versions. 🚀

Sorry for the long delay! 🙈 I wanted to personally address each issue/PR and they piled up through time, but now I'm checking each one in order.