Interpolate bash variable into a genrule's string parameter macro

We’d like to do something like

# foo/BUCK
for i in ['Linux', 'Darwin']:
  genrule(
    name = 'bar-' + i,
    # blah
  )

genrule(
  name = 'bar',
  cmd = 'cp $(location :bar-$(uname -s)) $OUT',
  out = 'my-plat-bar'
)

where we want to let people refer to //foo:bar that’s specific to their own system’s platform, but also allow them to refer to //foo:bar-Linux and //foo:bar-Darwin if they want to explicitly build the genrule for the other architecture.

Unfortunately, using bash interpolation within a string parameter macro like $(location {}) doesn’t work; it’d be nice if it did.

Maybe we just shouldn’t have the convenience of having a single build rule refer have different outputs depending on platform? Seems unfortunate, though 😦

(Context: we currently use import sys, an unsafe import, to do this from python instead of inside the genrule itself.)

[jiangty-addepar]

Oh, that helps! Thanks 😃

[ttsugriy]

I’m not sure what are you using sh_binary for, since having a dependency on a genrule is sufficient to create its output for the rule that depends on it. I think adding an executable = Trueto your genrule is all you need to use genrules directly.