Constants overwrite environment

[JonathanDoughty]

While testing some recipes that rely on environment variables

env:
    @env | sort

being the simplest example I can use I unexpectedly encountered

HEX=0123456789abcdef 
HEXLOWER=0123456789abcdef
HEXUPPER=0123456789ABCDEF

Curious as to where these came from I eventually tracked them down -- not to some tool that was part of my normal environment set up but to just internals added in ##2054

just being able to provide constants is, I suppose, fine (though why these merit a special definition is unclear; HEXLOWER and HEXUPPER seem superfluous to me and I wonder what slippery slope of constants may be in just's future). Exporting justconstants to recipes seems like a surprise waiting to happen, however. Under the current implementation, if the project environment I set up happens to use one of just's current or future constants then the result of set export is that my expected environment gets over-ridden in those cases. Future additions to just constants causing changed recipe execution is the scenario I anticipate.

Possible alternatives:

1. not export constants into the environment; or
2. constants not override any key already in the environment that set export creates; or
3. provide an explicit set export-constants or set export-no-constants for users who want/don't want that.

I don't know how easy any of those would be given rust's apparent OnceLock implementation. At the least, in my opinion, just's documentation on Constants should mention that these overwrite other environment definitions, and that users can override just "constants" with variable definitions if necessary.

[casey]

Thanks for the report! This is definitely a bug. Constants are supposed to be just variables only, i.e., not exported to the environment.

[casey]

Ahh, okay, do you have set export somewhere in your justfile? I suspect that's what's causing them to be exported. In any case, it's still a bug, since even with set export, I don't think constants that the user did not define should be exported.

[casey]

Fixed in #2449!

[casey]

The purpose of these constants, by the way is, with the choose(n, alphabet) function, which chooses n characters from the string alphabet. So you can generate a hex string, for example, with choose(32, HEXLOWER).