Automatic OPTIONS request with route schema

[samuelcolvin]

First check

Yes to all (great list of checks btw, I might copy them to pydantic 👍 )

Thank you

@tiangolo FastAPI is great. This is the first time I've used it in production and I'm really impressed by both the range of features and particularly the documentation. I've written and deployed web apps using django, flask, aiohttp, starlette and now fastapi. FastAPI is the only python web framework I've seen to come close to django in terms of quality of documentation, it's definitely now my go-to web framework.

Thank you for the amazing project, I feel really proud to have contributed to it indirectly.

Feature Request

The only thing I've seen missing from fastpi is support for informative OPTIONS requests for all/most/some endpoints, automatically included based in the route's definition.

I effectively want the following:

class LoginForm(BaseModel):
    email: EmailStr
    password: SecretStr

@app.post('/login/')
async def login(login_form: LoginForm):
   ...

@app.options('/login/', include_in_schema=False)
async def login_options():
    return LoginForm.schema(by_alias=True)

Without having to define the second endpoint. This is so my react frontend can build forms without having to duplicate the field definitions.

I guess it might have to be slightly more complex to include parameters, query args and body model(s).

I know I can get the information I need from /openapi.json, but that involves more processing in js and more data downloaded.

In the past when I've implemented a feature like this myself, I had to deal with OPTIONS requests associated with preflight checks separately, but that's relatively easy by looking for the Access-Control-Request-Method header.

I guess if this feature was to be approved it would have to be optional, default off. I guess through a keyword arg on FastAPI, include_router and each route.

[Vlatterran]

According to the specifications of OPTIONS method, i'm not sure if it is supposed to do what you want

If I understands correctly, you want to have a shortcut to the schema of some endpoints, while OPTIONS describing the whole path.

I think it'll be better to have such a shortcut by <METHOD> http:\example.net\docs<path> for the <METHOD> endpoint

[samuelcolvin]

No, I want the scheme for that URL, which is exactly what OPTIONS requests are for.

[gwerbin]

I just ran into this unexpectedly when I saw a bunch of HTTP 405 responses using Swagger UI. It looks like Swagger UI assumes that every endpoint supports OPTIONS. It doesn't seem to impede the ability to send requests in the UI, but I assume it's used for something, otherwise it wouldn't be there. I was surprised that HTTP OPTIONS wasn't supported by default for FastAPI routes, at minimum returning an empty response with the standard ALLOW header.

I also noticed that HEAD similarly was not supported by default, which can be useful for debugging and scripting. This again was surprising to me.

So here's my +1 for enabling both OPTIONS and HEAD by default in FastAPI routes.

[whysage]

Hello please check draft of PR for this issue https://github.com/tiangolo/fastapi/pull/10057

[whysage]

Hi, updated PR (fixed linters and tests, add default value False for add_auto_options_route) please review general approach https://github.com/tiangolo/fastapi/pull/10861

Tests will be added.

[whysage]

Tests were added. Please review. https://github.com/tiangolo/fastapi/pull/10861

@tiangolo @samuelcolvin

[whysage]

Hi, any comments on pull request?

[whysage]

A kind reminder about review of PR https://github.com/tiangolo/fastapi/pull/10861 @tiangolo @samuelcolvin @gwerbin @Vlatterran

[whysage]

Any updates on review https://github.com/tiangolo/fastapi/pull/10861 ? @tiangolo @samuelcolvin @gwerbin @Vlatterran

[gwerbin]

Sorry @whysage, I haven't had much free time. I will try to block out some time for it on Sunday night. Note that I'm not a repo maintainer so you will still need approval from someone else.

[whysage]

@gwerbin thanks!

[whysage]

Hi, please review https://github.com/tiangolo/fastapi/pull/10861 @tiangolo @samuelcolvin @gwerbin @Vlatterran

[tiangolo]

@whysage thanks for the interest, I'll review it once I get there, I have many other things to review and do.

Please do not ping us as it adds additional overhead and work reviewing the pings, and that's an effort I/we could have invested in reviewing PRs, so that we could get to yours faster.

If you want to accelerate the process, you could help with everything else, answering questions, reviewing other PRs, etc: https://fastapi.tiangolo.com/help-fastapi/#help-maintain-fastapi