[bug] Weird side effects when using {/} substitution at the edges of args under Windows

[webknjaz]

Basically, given the following config

[testenv]
commands = some-script.py path{/} {posargs} --more-args

or even

[testenv]
commands = 
  some-script.py \
    path{/} \
    {posargs} \
    --more-args

tox converts {/} into \ early and then treats it as if it's typed into the config by the end-user and is an escaping character.

I was very puzzled to see that the program I'm invoking via tox r -- few more args was getting path few as a single argument (sys.args was getting something like ["path few", "more", "args"]). And only on Windows 🤯! But after staring at it long enough, it occurred to me that it's just an escape character.

P.S. I'm using path{/} because I have a habit of visually separating directory and file path values by that trailing slash. Of course, the workaround is to drop it, but I believe it reveals a deeper issue here. I haven't attempted doing any debugging, but still wanted to document this magical behavior.

[webknjaz]

Interestingly, in the place where I got '{toxinidir}{/}requirements{/}', it seems to work. So quotes to the rescue I guess...

[gaborbernat]

Yeah, because is the trailing \ the issue, so a quote sidesteps the problem. Perhaps the line collapse needs to happen before any substitution and none afterward.