pkg_deb: allow passing deb and changes directly

[amscanne]

(More detail in the commit.)

I've knocked this out quickly in anticipation of some feedback on a better way to solve this problem. Please let me know if I'm holding it wrong!

[amscanne]

This is actually broken in a non-trivial way, because the test depends on being able to refer to out_deb and out_changes explicitly in its runfiles. (Is this something that anyone does outside the test? I'm not sure.) I could change the test behavior, but I'd like to get guidance on this first.

Note that other people have hit this problem as well:
https://stackoverflow.com/questions/56190105/selecting-different-values-for-pkg-debs-package-and-architecture-attributes#new-answer

[amscanne]

Okay, I think I misunderstood the constraints. The latest patch just lets you pass a select for the architecture, so that you can at least work around the problem. The API for pkg_deb is otherwise unchanged.

[aiuto]

Can you start with an issue for this where we can come up with an overall design. The package_file_name attribute from pkg_tar will be available to pkg_dep too. That takes care of half this PR in a uniform way across rules.
Do we need that same capabilty for changes or is there a default format for changes which we should always use?

[matzipan]

AFAIU the problem is that you can't pass a select to architecture. And I think the proposed workaround was to pass debs and changes from the outside so this wouldn't be a blocker.

[aiuto]

I think #282 makes this obsolete. The net effect of that PR is that you can set changes explictly if you want. But if you don't, we use basename(package_file_name).changes. In turn, package_file_name might be built from the defaults or computed from things only known at build time (like cpu).

[aiuto]

Sorry, @matzipan, I didn't actually answer your question.

I don't understand why you are saying that architecture is not select()able. I just tried using a select for architecture, along with the defaulting for package_file_name and it just worked.

pkg_deb(
    name = "deb_select_arch",
    data = ":example1",
    description = "what it does",
    maintainer = "someone@somewhere.com",
    package = "foo_b",
    version = "1",
    architecture = select({
        ":special_build": "NewCPU",
        "//conditions:default": "x36",
    }),
)


$ bazel build :deb_select_arch
Target //:deb_select_arch up-to-date:
  bazel-bin/foo_b_1_x36.deb
$ bazel build :deb_select_arch --define=SPECIAL=1
Target //:deb_select_arch up-to-date:
  bazel-bin/foo_b_1_NewCPU.deb

Of course, looking at the stackoverflow question, I see that it might not have been selectable before #282, but all the output file computations are made more rationally now.

[matzipan]

Hi aiuto,

Thanks for the response. I was not aware of #282, which seems to address that. I think I've seen it in other Bazel extensions as well, so it's interesting that now I know how this can be fixed (I think it was rules_docker).

Andrei

[aiuto]

#282 is submitted now. This PR might be obsolete.

[amscanne]

Based on your comment above, I’m happy and will close this issue. I’ll reopen if there’s something that isn’t working as expected.