oci_push rule fails on osx when pushing a linux image

[codesuki]

While adding support for oci_image to rules_k8s I ran into the following issue.

I am pushing an image with --platforms=@io_bazel_rules_go//go/toolchain:linux_amd64 from my local osx machine and get the following error

push_push_api_image.sh: line 52: ../aspect_bazel_lib~~toolchains~jq_linux_amd64/jq: cannot execute binary file

Some investigation showed that I should set --extra_execution_platforms=@platforms//host, but this fails with the same error.

Investigating some more I found bazelbuild/bazel#19645 and https://github.com/bazel-contrib/rules_oci/blob/main/oci/private/push.bzl#L142-L155.
Together with the the fact that I am using Bazel 7.x and this commit bazelbuild/bazel@c602cec

Subsequent settings of --extra_execution_platforms now override previous settings, instead of adding them to a list.

I figured I can make it work with the snippet below. Instead of overwriting extra_execution_platforms, we preserve previous contents.

# Helper rule for ensuring that the crane and yq toolchains are actually
# resolved for the architecture we are targeting.
def _transition_to_target_impl(settings, _attr):
    return {
        # String conversion is needed to prevent a crash with Bazel 6.x.
        "//command_line_option:extra_execution_platforms": [
            str(platform)
            for platform in settings["//command_line_option:extra_execution_platforms"] + settings["//command_line_option:platforms"]
        ],
    }

_transition_to_target = transition(
    implementation = _transition_to_target_impl,
    inputs = ["//command_line_option:platforms", "//command_line_option:extra_execution_platforms"],
    outputs = ["//command_line_option:extra_execution_platforms"],
)

I am not sure if this is the 'real' fix, but if it were then it would at least need a check for the Bazel version to do the right thing.

[fishy]

We are seeing the same issue. I think maybe there's a better way to cross-build container image for linux-amd64 on other host platforms than adding --platforms=@io_bazel_rules_go//go/toolchain:linux_amd64 to the command line, but I didn't find doc describing other ways in rules_oci. Currently we reverted back to rules_oci version 1.7.6 which is the last version it works on mac without any additional hack.

@codesuki can you describe more about how the transition solution works?

[codesuki]

Reading all these issues it certainly feels like the underlying issues are not resolved even with that transition.

Anyhow, for why the transition broke for me with Bazel 7 was the change I linked to above.

The transition code in rules_oci adds the platform value to the extra_execution_platforms. In Bazel < 7 this worked because it was additive.
So when I specify --extra_execution_platforms=@platforms//host to make oci_push work the transition just added to it.
With the Bazel 7 change it overrides and loses my --extra_execution_platforms=@platforms//host which results in oci_push failing because it's built for linux.

[lionelfleury]

Having the exact same problem when wanting to build a linux/amd64 container on a darwin/arm64 machine.

I think this is a bug because binaries for push are transitioned to target platform. They should reflect execution platform instead...

[ahans]

It also happens when trying to push linux/arm64 images from a linux/amd64 host.

[ahans]

FWIW, @codesuki's patch fixes it for me (with Bazel 7.3.2), so thanks a lot for that! However, reverting #590 fixes it as well without requiring --extra_execution_platforms=@platforms//host. I wonder why that was introduced in the first place and what's the use case here? Isn't oci_push something that we would always run on the host and not on the target?

[manuelnaranjo]

It also happens when trying to push linux/arm64 images from a linux/amd64 host.

Ok this sounds like something that's trivial to add a unit test for then, and validate that things work as expected. Cross compiling from darwin is not so trivial as it requires darwin based runners

[thesayyn]

I think i'll defer to @EdSchouten