[FR]: Document how to use gazelle Kotlin plugin from a bzlmod project

[gonzojive]

What is the current behavior?

The documentation for setting up the Kotlin gazelle plugin is a bit sparse. I can't tell how to compile it into a custom gazelle binary from a bzlmod project.

Describe the feature

Document how to install the gazelle plugin in a bzlmod project. For example, I have the following MODULE.bazel. What's required to plug in Kotlin gazelle?

module(
    name = "dir_find_and_replace",
    version = "0.0.1",
)

bazel_dep(name = "rules_kotlin", version = "1.9.6")
bazel_dep(name = "rules_jvm_external", version = "6.4")

maven = use_extension("@rules_jvm_external//:extensions.bzl", "maven")

# When updating a dependency, run REPIN=1 bazel run @maven//:pin
maven.install(
    artifacts = [
        "com.google.truth:truth:1.1.2",
        "junit:junit:4.13.2",
    ],
    lock_file = "//:maven_install.json",
    repositories = [
        "https://repo1.maven.org/maven2",
    ],
)
use_repo(maven, "maven")

bazel_dep(name = "gazelle", version = "0.39.0", dev_dependency = True)
bazel_dep(name = "rules_go", version = "0.50.1", dev_dependency = True)

go_deps = use_extension("@gazelle//:extensions.bzl", "go_deps")
go_deps.from_file(go_mod = "//:go.mod")

# BUILD.bazel

load("@gazelle//:def.bzl", "gazelle", "gazelle_binary")

# gazelle:prefix github.com/bazel-gazelle/tests/bcr
gazelle_binary(
    name = "gazelle",
    languages = [
        # "@gazelle_kotlin//gazelle/kotlin:kotlin", Presumably I want something like this
        "@gazelle//language/go",
        "@gazelle//language/proto",
    ],
    visibility = ["//visibility:private"],
)

---

For the sake of getting something working, I split off the gazelle code from the rest of aspect-cli, made it work with bzlmod instead of WORKSPACE, and started using the fork in an example project. Would Aspect prefer to keep the gazelle plugin(s) within aspect-cli, or are you open to splitting of the gazelle plugins into a separate repo or repos? If kept in this repo, could/should they be packaged into distinct bzlmod module (by putting a MODULE.bazel file and a go.mod file within /gazelle or something, presumably)?

From the outside, having a tightly scoped project concerned only with the Kotlin gazelle plugin could be nice and simple. It might make it slightly more inviting to contribute improvements. But Aspect might have its reasons for keeping the gazelle stuff inside aspect-cli.