How to use Skylib unittest to test cpp compiler command line?

[Konstantin]

We have custom C++ compilation rule which invokes cc_common.compile and try to add a test that it properly translates its attributes to the compiler command line parameters. 

My attempt at the test code looks like this:

load("@bazel_skylib//lib:unittest.bzl", "analysistest", "asserts")

def _local_includes_test_impl(ctx):

    env = analysistest.begin(ctx)

    target_under_test = analysistest.target_under_test(env)

    actions = analysistest.target_actions(env)

    compile_action = None

    for action in actions:  # action has type Action. See https://bazel.build/rules/lib/Action

        if action.mnemonic == "CppCompile":

            compile_action = action

            break

    if not compile_action:

        fail("target_under_test %s does not produce expected action CppCompile" % target_under_test.label)

    asserts.equals(env, 1, len(compile_action.args))

    args = compile_action.args[0]  # args has type Args.

    print(args)

    return analysistest.end(env)

local_includes_test = analysistest.make(_local_includes_test_impl)

At this stage we get variable "args" of type Args, but there is absolutely no way to check its contents! I even can print it and see that it it contains correct representation of the compiler command line, but even that string representation cannot be obtained in the test!

Documentation recommends to try "argv" instead of "argc", but the experiment shows that it is None in this case. 

I am stumped. How we supposed to use unittest to analyse the command lines of the generated actions?

Thank you!

Konstantin

[Alex Humesky]

Unfortunately it looks like the CppCompile action was only relatively recently updated to report argv:

February: https://github.com/bazelbuild/bazel/commit/aaba5be3d50b642ad3d9bccada8971a06c68c123

October: https://github.com/bazelbuild/bazel/commit/950c206c38c4cce03c55f9d875d355b67b8354df

Luckily, the baseline for bazel 6.0 hasn't been selected yet, so I would expect both of those to be in the next release:

https://github.com/bazelbuild/bazel/issues/16159

The commit from February is in bazel pre-release versions, so you could try the test with a pre-release. The commit from October deals with making argv from CppCompile report the real args when a param file is used (guarded by a flag), and that's not in a pre-release yet. So if you need that, you could build bazel from head, or wait for another pre-release to try this out.

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[Konstantin]

Uh-huh. Good to know!

[Neal Norwitz]

On Mon, Oct 17, 2022 at 6:05 PM 'Alex Humesky' via bazel-discuss <bazel-...@googlegroups.com> wrote:

Luckily, the baseline for bazel 6.0 hasn't been selected yet, so I would expect both of those to be in the next release:

https://github.com/bazelbuild/bazel/issues/16159

Can you give us any updates/plans about 6.0? When might it be cut?  When is the earliest it could be fully released?  A list of blockers?  An issue we could track to get updates? etc

Thanks,

n

[Alex Humesky]

That info can be found at the bazel 6.0 tracking issue here:

https://github.com/bazelbuild/bazel/issues/16159