alias() doesn't support surfacing a *_flag to the command line

[afq984]

Description of the feature request:

load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")

config_setting(
    name = "my_flag_enabled",
    flag_values = {
        ":my_flag": "true",
    },
)

bool_flag(
    name = "my_flag",
    build_setting_default = False,
)

alias(
    name = "my_flag_alias",
    actual = ":my_flag",
)

bazelisk build --//:my_flag_alias //:my_flag_enabled
INFO: Invocation ID: 4dda7f49-80a0-4ae1-be58-37d1ebd1876d
ERROR: //:my_flag_alias :: Unrecognized option: //:my_flag_alias

Which category does this issue belong to?

Configurability

What underlying problem are you trying to solve with this feature?

We were trying to expose user-friendly flags aliases to generated repositories, so users don't have to type the full path of packages.

E.g. people can use --@portage//target/sys-apps/attr:2.5.1_incremental instead of --@portage//internal/packages/stage2/target/board/portage-stable/sys-apps/attr:2.5.1_incremental

Which operating system are you running Bazel on?

Linux

What is the output of bazel info release?

development version

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

cat .bazelversion 
bbc4b12eb562de5e5daeec9700fa258dfdc5a51b

What's the output of git remote get-url origin; git rev-parse master; git rev-parse HEAD ?

No response

Have you found anything relevant by searching the web?

No response

Any other information, logs, or outputs that you want to share?

For our use case, we also need the alias's actual to be in a select.

e.g. something like alias(name = "incremental", actual = select({"//bazel/stage1": "//internal/stage1/pkg/incremental", "//bazel/stage2": "//internal/stage2/pkg/incremental"})

Not sure if it is something possible to support.

[afq984]

I initially confused this with #13463, which was aliasing on the config_setting instead of the bool_flag.

[gregestren]

Can https://bazel.build/reference/command-line-reference#flag--flag_alias work for you?

I thought we had some support for what you describe, but I guess not?

[afq984]

Our build targets are, generated from a repository rule which inspects local build manifests (which we are slowly migrating away from).

As the targets are dynamic, we cannot use a static bazelrc with --flag_alias for that.

I think if we write a bazelrc file to be imported by the main file, in the tools/bazel wrapper, then we can get dynamically generated aliases.

It might be hard to pull off though. The build manifest analysis is expensive and lives inside a Bazel invocation already.

[iancha1992]

A fix for this issue has been included in Bazel 7.2.0 RC1. Please test out the release candidate and report any issues as soon as possible.
If you're using Bazelisk, you can point to the latest RC by setting USE_BAZEL_VERSION=7.2.0rc1. Thanks!