Using as a native_binary / native_test

[novas0x2a]

This is honestly probably a doc suggestion, I think, though I'm not quite sure how to phrase it. If you want to use the multitool binary as a tool, i.e. as part of the build, it seems like:

• If you want it to be safe under cross-compilation, you must use the :cwd target to ensure that there is a transition to cfg=exec (otherwise, when you run with --platforms <incompatible>, it'll download the wrong binary)
• If you want it to work on windows, you have to use a file extension that matches the original one (in other words, .bat).

I think this means that this is exactly what you need to invoke (for, let's say, using ruff as a test):

load("@bazel_skylib//rules:native_binary.bzl", "native_test")

native_test(
    name = "ruff_lint",
    # use cwd to run the binary through a cfg=exec label, so things don't break when target != exec
    src = "@multitool//tools/ruff:cwd",
    # use .bat because unix doesn't care about the extension, but windows won't work otherwise
    out = "ruff_lint.bat", 
    args = [
        "--version",
    ],
    data = [
        "@multitool//tools/ruff:cwd",
    ]
)

I'm curious if you know if a better way to handle this.

[mark-thm]

When using multitool binaries in our builds we typically make a custom rule where we can specify the configuration.

Our ruff wrapper is an aspect that sets cfg=“exec”, for instance. The specifics around producing a .bat file is generally true of windows and not something specific to the executables we make here.

Absent a custom rule, I think you need a transition, but frankly I’m not quite literate enough to give you an example.

[novas0x2a]

I was largely trying to avoid needing a custom rule to handle it, instead trying to make it work with just a custom macro to avoid needing to reimplement stuff like native_test. I mostly mention this as a doc fix because it took me a few (distracted) hours to figure out what was happening in our windows build.

No additional transition is needed if you use the :cwd target, because the transition is built into that target already. (The thing I put into the description is a complete, working example if all you want to do is invoke ruff --version. Obviously, if you want to run ruff check with a custom config, you need a few more things)