✨ Add allow disabling redirect_slashes at the FastAPI app level

[cyberlis]

Right now redirect_slashes parameter in sub routers created with APIRouter ignored, because only main router's redirect_slashes inside FastAPI class is taken into account. FastAPI class creates new router without redirect_slashes argument and that's why router always uses default value redirect_slashes=True and always redirects on trailing slashes.
https://github.com/tiangolo/fastapi/blob/master/fastapi/applications.py#L69

Here is how to reproduce this problem

from fastapi import FastAPI
from fastapi.routing import APIRouter

router = APIRouter(redirect_slashes=False)

@router.get('/hello/')
def hello_page() -> str:
    return 'Hello, World!'

app = FastAPI()
app.include_router(router)

And if you request page http://127.0.0.1:8080/hello (without trailing slash) you will be redirected even with redirect_slashes=False

uvicorn main:app
INFO:     Started server process [96046]
INFO:     Waiting for application startup.
INFO:     Application startup complete.
INFO:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
INFO:     127.0.0.1:57330 - "GET /hello HTTP/1.1" 307 Temporary Redirect
INFO:     127.0.0.1:57330 - "GET /hello/ HTTP/1.1" 200 OK

I added redirect_slashes to __init__ method of FastAPI class and passed it to router's constructor.
That way I can change trailing slashes redirect behaviour globally for application instance.

[cyberlis]

please review @tiangolo

[StashOfCode]

Hey @tiangolo, any news on this pr? It solves a lot of hassle with 'slash/no slash' related redirects @Kludex @jaystone776

[sk-]

LGTM

[sk-]

@Kludex @tiangolo is there any chance this PR could be reviewed? I did review the code myself and it looks good and tested.

Some others have also spent the time writing a PR solving the same issue. See #5392.

Our motivation for having this merged:
We have stumbled across this issue, because some times customers make the mistake of adding/removing the trailing slash which increases the latency and later on they complain that our provided endpoints are slow.

It'd be great if we could control whether redirect_slashes is set.

[github-actions]

📝 Docs preview for commit 434f67c at: https://63457ff2dc12071d5f3bbfa3--fastapi.netlify.app

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (cf73051) 100.00% compared to head (4bfaa00) 100.00%.

❗ Current head 4bfaa00 differs from pull request most recent head 3ecac8b. Consider uploading reports for the commit 3ecac8b to get more accurate results

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #3432   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          540       541    +1     
  Lines        13969     13972    +3     
=========================================
+ Hits         13969     13972    +3     

Impacted Files	Coverage Δ
fastapi/applications.py	100.00% <ø> (ø)
tests/test_router_redirect_slashes.py	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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[github-actions]

📝 Docs preview for commit 316ad61 at: https://63494c3b2c995530f46aa4ab--fastapi.netlify.app

[cyberlis]

@Kludex @tiangolo please review PR

[github-actions]

📝 Docs preview for commit 4bfaa00 at: https://6351aa4b4b09510865226f15--fastapi.netlify.app

[github-actions]

📝 Docs preview for commit 56c7bd4 at: https://639ce3792b35ad02dfe481d1--fastapi.netlify.app

[xpinguin]

Hi guys, could you please update us about the status of this PR? We're waiting for this feature in master for a long time already and custom hacks aren't good. Thanks a lot!

[cyberlis]

Hi guys, could you please update us about the status of this PR? We're waiting for this feature in master for a long time already and custom hacks aren't good. Thanks a lot!

I'll update it tomorrow

[github-actions]

📝 Docs preview for commit 22499af at: https://644c43c0587f9e1ec747a7b2--fastapi.netlify.app

[cyberlis]

Hey @tiangolo, @Kludex
This PR is ready to be merged
It has tests and people still need it

Could you review it, please

[Kludex]

Starlette class doesn't have this parameter. It only exists on the Router class in Starlette. jfyk @tiangolo

[tiangolo]

Makes sense, thank you @cyberlis! 🚀

Thanks everyone for the reviews, especially for commenting that you tried out the code and confirming that this works and is useful for you. 🙇 🍰

This will be available in FastAPI 0.98.0, released in the next hours. 🎉