nixpkgs_local_repository dependency change doesn't invalidate nixpkgs_package

[jcpetruzza]

Given a WORKSPACE with something like this:

nixpkgs_local_repository(
    name = "nixpkgs",
    nix_file = "//my/nixpkgs/default.nix",
    nix_file_deps = [ "//my/nixpkgs/something.nix"],
)

nixpkgs_package(
    name = "foo",
    attribute_path = "foo",
    repository = "@nixpkgs",
)

I'd expect that changes to my/nixpkgs/something.nix will force @foo to be rebuilt, but it seems that it doesn't and only changes to my/nixpkgs/default.nix will do. We had some reproducibility issues because of this, our workaround was to merge everything in one big file and avoid nix_file_deps.

From looking quickly through the code, the label "@nixpkgs" corresponds to @nixpkgs//:nixpkgs and this is symlinked to my/nixpkgs/default.nix, so iiuc, from the point of view of bazel, @foo only depends on that file, and not on my/nixpkgs/something.nix. I guess @nixpkgs//:nixpkgs could instead be defined to be a filegroup() containing the given nix_file and everything in nix_file_deps?

[aherrmann]

Thanks for reporting this!

The following should work correctly, i.e. adding nix_file_deps to the nixpkgs_package call:

nixpkgs_package(
    name = "foo",
    attribute_path = "foo",
    repository = "@nixpkgs",
    nix_file_deps = [ "//my/nixpkgs/something.nix"],
)

As you describe, it looks like right now nix_file_deps of nixpkgs_local_repository does not affect nixpkgs_package. I'm not sure that a filegroup will work here, since we're in the context of a repository_rule. However, what may work is to create additional symlinks in nixpkgs_local_repository for nix_file_deps.

[jcpetruzza]

Just to clarify, what I meant with the filegroup() is to define it in the BUILD.bazel file generated for the @nixpkgs repo, similar to what is done with, say, :bin and :lib in the external repositories created with nixpkgs_package.

I'm not sure creating more symlinks in nixpkgs_local_repository would make a difference. It is already creating templates from them and they get updated on changes.

[aherrmann]

I'm not sure creating more symlinks in nixpkgs_local_repository would make a difference. It is already creating templates from them and they get updated on changes.

Oh, it is indeed. Sorry, I overlooked that.

Just to clarify, what I meant with the filegroup() is to define it in the BUILD.bazel file generated for the @nixpkgs repo, similar to what is done with, say, :bin and :lib in the external repositories created with nixpkgs_package.

I see, and nixpkgs_package would then depend on that filegroup? That might work, do you want to give it a shot and open a PR if it works?

[mboes]

@jcpetruzza still working on this?

[jcpetruzza]

Sorry, I haven't had the time to work on this yet. If someone wants to look into it, by all means, go ahead! 🙂