Tweaks to scalafmt rules/script to support bazel test wrappers

[virusdave]

Relates to #994

With these changes, I can use a macro to place a wrapping sh_test
target around this script, and change the phase ordering to put
phase_scalafmt before the runfiles phase, and suddenly it works
as intended!

NB: If this change is acceptable to folks, then it might be worth
changing the default phase placement for ext_scalafmt to place
it before runfiles by default.

Example use:

In custom bzl file, I have:

_enable_format_targets_and_tests_by_default = True

_ext_scalafmt = dicts.add(
    _base_ext_scalafmt,
    {"attrs": dicts.add(
        _base_ext_scalafmt["attrs"],
        {"format": attr.bool(
            default = _enable_format_targets_and_tests_by_default,
            doc = "Enable the check-format and auto-format synthetic run targets (foo.format-test and foo.format respectively)",
        )},
    )},
    {"phase_providers": [
        "@//path/to/some/buildfile:phase_scalafmt",
    ]},
)

scala_library = make_scala_library(_ext_scalafmt)  # etc for other rule types

def maybe_add_format_test(**kwargs):
    if (kwargs.get("format", _enable_format_targets_and_tests_by_default)):
        name = kwargs["name"]
        sh_test(
            name = "{}.format-test.target".format(name),
            srcs = [":{}.format-test".format(name)],
            data = [
                ":{}".format(name),
            ],
            local = True,
        )

def _scalafmt_singleton_implementation(ctx):
    return [
        _ScalaRulePhase(
            custom_phases = [
                ("-", "runfiles", "scalafmt", _phase_scalafmt),
            ],
        ),
    ]

scalafmt_singleton = rule(
    implementation = _scalafmt_singleton_implementation,
)

then in path/to/some/buildfile/BUILD.bazel, I have:

load("//path/to/above/my_rules.bzl", "scalafmt_singleton")

scalafmt_singleton(
    name = "phase_scalafmt",
    visibility = ["//visibility:public"],
)

Description

Motivation

[liucijus]

Thanks, @virusdave

[liucijus]

@virusdave please fix formatting for:
./scala/private/phases/phase_scalafmt.bzl # reformat

You can run ./lint.sh to get it fixed

[virusdave]

@virusdave please fix formatting for: ./scala/private/phases/phase_scalafmt.bzl # reformat

You can run ./lint.sh to get it fixed

Done! Thanks.

[virusdave]

Thoughts on this?

NB: If this change is acceptable to folks, then it might be worth
changing the default phase placement for ext_scalafmt to place
it before runfiles by default.

If it's agreed upon, i'm happy to make a followup change to do so.

[liucijus]

NB: If this change is acceptable to folks, then it might be worth
changing the default phase placement for ext_scalafmt to place
it before runfiles by default.

Yeah, help here is appreciated. Thanks for taking this! Do you mean tweaking what happens with make_scala_library?

[virusdave]

NB: If this change is acceptable to folks, then it might be worth
changing the default phase placement for ext_scalafmt to place
it before runfiles by default.

Yeah, help here is appreciated. Thanks for taking this! Do you mean tweaking what happens with make_scala_library?

I meant this: #1347