file location relative to filegroup

[Peter Grarup]

I have a BUILD file that exposes a set of config files in a filegroup.

filegroup(

  name = "config_files",

  srcs = glob(["**/*"]),

  visibility = ["//visibility:public"],

)

some of the files are located in subfolders relative to the BUILD file.

when I use this filegroup in a starlark rule the files contain the full path. Is there a way to get the root from where the file group was created?

[Brian Silverman]

pkg_tar(strip_prefix = ".") does this. rules_pkg has a system for mapping paths, I find that passing files around like that is usually easier than implementing the logic myself.

The core of the logic is applying dest_path to each element of `src[DefaultInfo].files.to_list()`. That's a function which determines a path, and removes a prefix if it's present. In the `strip_prefix = "."` case, this prefix is `compute_data_path(ctx, ".")`, which evaluates to `ctx.label.package`. The path itself is calculated in `safe_short_path` like this:

    working_path = file_.path
    if not file_.is_source:
        working_path = working_path[len(file_.root.path)+1:]

I think `working_path[len(ctx.label.package):]` will give you the result you're looking for, assuming your filegroup and your rule are in the same package. If not, `ctx.attr.src.label.package` will tell you the package for the filegroup being passed as an attribute.

If you're looking for any other tricky path manipulation, I find that rules_pkg has lots of examples.

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