Bazel wants full dependency graph for incompatible targets - why aren't they just skipped?

[carlosgalvezp]

Description of the problem / feature request:

Hi!

I have a target that is only compatible with the aarch64 platform:

cc_binary( 
    name = "foo",
    target_compatible_with = ["@platforms//cpu:aarch64"], 
    deps = [ "//foo:bar", ] 
)

Now, the bar dependency comes in two flavors, so I have an alias:

alias(
      name = "bar",
      actual = select({ 
            # Simplified syntax here 
            "aarch64_linux" : ":bar_linux",
            "aarch64_qnx": ":bar_qnx", 
       }) 
)

Now, my problem is that when I build for x86 using wildcard, Bazel complains that it cannot find any bar for x86. And that's of course expected - there's no bar or x86! However why is Bazel complaining here? I specified that this target is incompatible with x86, so it shouldn't need to analyze it. Why is it doing that?

If I remove the bar dependency, Bazel just skips the target and exits gracefully without errors.

I could solve this problem adding a default condition for bar, but I don't want that. It will silence a useful warning. If I ever want to support a 3rd aarch64 version, the default condition will silence the warning without prompting me to add a 3rd aarch64 version of bar.

I also don't want to add a select in the deps field of the cc_binary either - it's redundant and adds noise. I already specify that the target is only compatible withaarch64. I don't need to add the deps only for aarch64.

Is this expected? Is there any other way I could solve this problem?

Thanks!

Feature requests: what underlying problem are you trying to solve with this feature?

I want Bazel to ignore incompatible targets, without it trying to find its dependencies (which may not exist at all for an incompatible platform)

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

See above.

What operating system are you running Bazel on?

Ubuntu 18.04

What's the output of bazel info release?

release 5.0.0-pre.20210907.1

Have you found anything relevant by searching the web?

Nothing on the web. Asked in bazel-discuss without answer.

[gregestren]

@carlosgalvezp - I see there's followup discussion on the bazel-discuss thread. Which parts of this issue are still pending?

[gregestren]

I think #14096 will fix this, although it's a work in progress (still under review, which will tak a few more iterations to land). That fixes #12897. I'll mark this a dupe for issue queue cleanliness.

[gregestren]

Duplicate of #12897