Does not prebuilt_cxx_library.static_lib support $(location //:target)？ about buck2

[zjturner]

You probably need to make a rule that can export a subpath, then you can use tge static_lib=“:foo” syntax

[cjhopman]

Yep, you need it to be the default output of a target or subtarget. What kind of rule is //:ext-link? If it's a genrule, that already has support for adding subtargets for paths in its output. If it's an http_file/archive, i'm not sure it has that support but it seems like it'd be a nice thing to add. That'd be something like:

http_archive(
  name = "ext-link",
  named_outs = { "liblef.a": "/opt/b28/s-5.8.003/linux_x86_64_rhel7/lib/liblef.a"}
  ...
)

prebuilt_cxx_libary(
   static_lib = '//:ext-link[liblef.a]',
   ...
 )

[zjturner]

As a temporary workaround though (until http_archive supports it natively), you can also just write a rule that takes a target (such as an http_archive) as a dep, and re-export it.

def _inner_path_impl(ctx):
    original_default_output = ctx.attrs.target[DefaultInfo].default_outputs[0]

    return [
        DefaultInfo(default_outputs = [original_default_output.project(ctx.attrs.subpath)])
    ]

inner_path = rule(
    impl = _inner_path_impl,
    attrs = {
        "target": attrs.dep(providers = [DefaultInfo]),
        "subpath": attrs.string()
    }
)

Then you use it like this:

http_archive(
  name = "_ext-link",
  named_outs = { "liblef.a": "/opt/b28/s-5.8.003/linux_x86_64_rhel7/lib/liblef.a"}
  ...
)

inner_path(
    name = "ext-link",
    target = ":_ext-link",
    subpath = "opt/b28/s-5.8.003/linux_x86_64_rhel7/lib/liblef.a"
)

prebuilt_cxx_libary(
   static_lib = '//:ext-link',
   ...
 )