How to get glob results from the different package?

[Konstantin]

I have a macro running in one package. In that macro I need to know what files are present in another package. I can run glob in the second package to get the list of files, but I don't see a way to pass that list to the macro in the first package. Any clue?

Thank you!

Konstantin

[Alex Humesky]

Typically for one package to get files from another package, you would define a file group in the other package with the files you're interested in:

foo/BUILD:

filegroup(

  name = "files",

  srcs = glob(["*.ext"]),

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

)

bar/BUILD:

java_binary(

  ...,

  resources = ["//foo:files"],

  ...,

)

However, a macro cannot inspect the values or providers of a target (i.e. //foo:files). So the next thing one might try is to glob the files and put that into a variable:

foo/BUILD:

FILES = glob(["*.ext"])

but the problem then is that you can't load that variable into another BUILD file:

load("//foo:BUILD", "FILES")

def macro(...):
  if "foo" in FILES:
    ...

that would give:

ERROR: BUILD:1:6: in load statement: The label must reference a file with extension '.bzl'

Is there any way that you can move what you'd like to do into Starlark? Then you can have a "srcs" attribute or similar, put the filegroup in there, and it would work as usual in Starlark.

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[Alex Humesky]

and by "into Starlark", I mean into a Starlark rule (macros are still Starlark afterall)

One other option might be to merge the packages together, then the glob() will work (since globs don't cross package boundaries), but I don't know if that works with the constraints you have.

[Konstantin]

Alex, thank you for your answer! 

Unfortunately what I wanted does not seem to be possible. I cannot move the logic into a rule and I cannot merge packages. 

For my specific case I was able to work around this problem without globbing files from another package, but my workaround is not reusable in general.

Konstantin

[Alex Humesky]

Gotcha, yeah I'm not sure that this is possible, glad though that you were able to find a workaround!

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