Why can't we get an Artifact's parent directory?

[cbarrete]

https://buck2.build/docs/api/build/Artifact/ explains that we have to use cmd_args for that use case, but it's quite cumbersome.

Is there a reason for this limitation, or is it just a matter of someone doing the work and submitting a PR?

Furthermore, would it be possible/acceptable to add a parent_dir string parameter macro? This would be very helpful in cleaning up BUCK files that need to reference the directories in which artifacts are produced (e.g. adding them to some PATH-like env var).

[cormacrelf]

I think the limitation is that someone needs to design a type to hold the parent directory. It can't be Artifact. If you have a projected artifact, the parent directory is well defined as an Artifact itself and you could therefore return an Artifact for .parent_dir(). But a source Artifact would not be able to do that. The parent directory is in the source tree. Buck doesn't represent these. So it needs its own type. Maybe it could be parent_dir() -> Artifact | ParentDirectory depending on the Artifact type.

You would basically write a type that emulates cmd_args(art, parent=1). I don't think it can have any other abilities.