Handlers with path variables are used even if parent route exists

Describe the bug Prior to Sanic 21, a route handler for /foo/ would be used instead of one for /foo/<var>/ if a request was made for GET /foo/, but now the second handler is called with an empty string for <var>.

Is this the intended behaviour - as in I should handle the case where the variable is empty instead of having a separate route? If so I’d have expected my example to throw a sanic_routing.exceptions.RouteExists to prevent me making this mistake.

Code snippet

from sanic import Sanic
from sanic.response import json

app = Sanic("My Hello, world app")

@app.route('/foo/')
async def test(request):
    return json({'hello': 'world'})

@app.route('/foo/<var>/')
async def myreq(request, var):
    return json({'hello': var})

if __name__ == '__main__':
    app.run()

Expected behavior Running the snippet above, I’d expect to see:

❯ curl localhost:8000/foo/bar/
{"hello":"bar"}%        
❯ curl localhost:8000/foo/
{"hello":"world"}%                                                                                                                                                            

(which I what happens on sanic 20.12.3)

Instead I get (on 21.6.2 and also 21.3.0):

❯ curl localhost:8000/foo/bar/
{"hello":"bar"}%                                                                                   
❯ curl localhost:8000/foo/
{"hello":""}% 

Environment (please complete the following information):

• OS: macOS Catalina 10.15.7
• Version: Sanic 21.6.2
• Python 3.7.9

Apologies if this should be on sanic_routing - I don’t really understand enough about the router to know!

[samdbmg]

Brill, cheers for the detailed explanation, and clarifying that the old behaviour was the bug, rather than the new. I’d be inclined to agree with @Tronic that the manual should probably spend a few words on the implications of strict_slashes/some form of the very useful explanation in https://github.com/sanic-org/sanic/issues/2239#issuecomment-921330915 - it’s quite hard to find the forum post from cold! If nobody beats me to it I’ll drop a docs PR in when I get some time.

[Tronic]

Another example of why strict_slashes should always be enabled (in new projects). Maybe need to put some emphasis on that on the manual?

I personally don’t ever expect web servers to do what the strict_slashes=False setting does. It could make sense to redirect a non-slashed request on a folder name to an URL with a trailing slash, but never to return the folder contents on an URL with a missing trailing slash. Also, the whole problem should exist only for manually typed in URLs.