runnable_binary: use package_relative_label

[lamcw]

With --enable_bzlmod, native.repository_name returns the apparent repo name (e.g. @foo~) instead of the canonical repo name. This can be a problem in the runnable_binary macro (esp. genrule targets) as rlocationpath may not be able to "see" srcs that are already listed, when some other modules depend on the runnable_binary target.

label '@@[unknown repo 'foo~' requested from @@foo~]//:foo_exe_fg' in $(location) expression is not a declared prerequisite of this rule. Since this rule was created by the macro 'runnable_binary', the error might have been caused by the macro implementation

Instead, package_relative_label should be used in the runnable_binary macro such that Bazel correctly converts the filegroup label in the context of the package currently being initialized.

[lamcw]

@jsharpe is there any plan to drop support for Bazel 5.4.0? package_relative_label is not supported until 6.1.0 bazelbuild/bazel#17435

[jsharpe]

As per the LTS schedule - https://bazel.build/release we'll continue to support 5.4.1 until Jan 2025.
Are you able to use bazel-contrib/bazel_features to detect support for package_relative_label and conditionally use it?

[lamcw]

Are you able to use bazel-contrib/bazel_features to detect support for package_relative_label and conditionally use it?

bazel_features does not support detecting package_relative_label -- instead I am using a hasattr guard to make sure it exists before invoking on it. Please take a look 🙏

[jsharpe]

LGTM!