Unexport environment variables per recipe using attribute

[W1M0R]

Currently, environment variables can be unexported at the justfile level, using unexport. This will unexport the environment variable for all recipes:

unexport GIT_EXTERNAL_DIFF
unexport GIT_PAGER

# only this recipe should not have GIT_EXTERNAL_DIFF and GIT_PAGER exported
diff-delta:
  git diff | delta --line-numbers

# and this recipe should respect the parent shell's GIT_EXTERNAL_DIFF and GIT_PAGER, but won't due to the unexport statements
diff-default:
  git diff

In some cases it is helpful to unexport (in a cross-platform way) an environment variable (or a list of environment variables) for only a specific recipe. One workaround is to use submodules, e.g. justfile-git-defaults.just and justfile-git-overrides.just, but this feels cumbersome.

Ideally, it would be nice to be able to unexport using an attribute:

[unexport("GIT_EXTERNAL_DIFF", "GIT_PAGER")]
diff-delta:
  git diff | delta --line-numbers

diff-default:
  git diff

Related:

1. Setting environment variables on a per-recipe basis without $-parameters #2408

[neunenak]

Seems to me that this issue should be combined with #2408 - the actual desired feature is a way to scope anything one can currently do with just variables to a single recipe (or maybe a group of recipes?), whether that's exporting, unexporting, etc.

[casey]

Yah, closing in favor of #2408, since whatever solution we come up with should handle both cases.