fix: Remove gazelle_binary import collision

[illicitonion]

What type of PR is this?

Bug fix

What package or component does this PR mostly affect?

internal/gazelle_binary

What does this PR do? Why is it needed?

These changes make the import aliases for the generated Go code in gazelle_binary longer to avoid collisions.

Without theses changes, importing 2 gazelle extensions with the same base path would fail to build the gazelle binary:

gazelle_binary(
    name = "gazelle_bin",
    languages = [
        # importpath = github.com/bazelbuild/bazel-skylib/gazelle
        "@bazel_skylib//gazelle/bzl",
        # importpath = github.com/bazelbuild/rules_python/gazelle
        "@rules_python//gazelle:gazelle_python_binary",
    ],
)

$ bazel build //:gazelle_bin
[...  snip]
bazel-out/darwin-fastbuild/bin/gazelle_bin_/langs.go:10:2: gazelle_ redeclared in this block
	bazel-out/darwin-fastbuild/bin/gazelle_bin_/langs.go:9:2: other declaration of gazelle_
bazel-out/darwin-fastbuild/bin/gazelle_bin_/langs.go:10:2: imported and not used: "github.com/bazelbuild/rules_python/gazelle" as gazelle_

The current generated bazel-out/darwin-fastbuild/bin/gazelle_bin_/langs.go file:

package main

import (
	"github.com/bazelbuild/bazel-gazelle/language"

	gazelle_ "github.com/bazelbuild/bazel-skylib/gazelle"
	gazelle_ "github.com/bazelbuild/rules_python/gazelle"
)

var languages = []language.Language{
	gazelle_.NewLanguage(),
	gazelle_.NewLanguage(),
}

With the proposed changes, this file would become:

package main

import (
	"github.com/bazelbuild/bazel-gazelle/language"

	github_com_bazelbuild_bazel_skylib_gazelle_ "github.com/bazelbuild/bazel-skylib/gazelle"
	github_com_bazelbuild_rules_python_gazelle_ "github.com/bazelbuild/rules_python/gazelle"
)

var languages = []language.Language{
	github_com_bazelbuild_bazel_skylib_gazelle_.NewLanguage(),
	github_com_bazelbuild_rules_python_gazelle_.NewLanguage(),
}

[achew22]

This seems like a good fix, but it's a smidge difficult to validate as just a code change. Is there any way you could add a test case for this?

You can create a new file internal/gazelle_binary_test.bzl with something like

load("@bazel_skylib//lib:unittest.bzl", "asserts", "unittest")
load(":gazelle_binary.bzl", format_import="_format_import", format_call="_format_call")

def _gazelle_binary_test_impl(ctx):
  env = unittest.begin(ctx)
  asserts.equals(env, "formatted_call", format_call("asdf"))
  asserts.equals(env, "formatted_import", format_import("asdf"))
  return unittest.end(env)

_gazelle_binary_test = unittest.make(_gazelle_binary_test_impl)

def gazelle_binary_test_suite(name):
  # unittest.suite() takes care of instantiating the testing rules and creating
  # a test_suite.
  unittest.suite(
    name,
    _gazelle_binary_test,
    # more tests if you want
  )

In internal/BUILD.bazel you can do:

load(":gazelle_binary_test.bzl", "gazelle_binary_test_suite")

gazelle_binary_test_suite(name = "gazelle_binary_tests")

[achew22]

Oops, replied in the wrong place. See previous comment

[illicitonion]

Done - do you know if there's a way to import private functions in tests?

I tried importing the private functions as you suggested in the example:

load(":gazelle_binary.bzl", format_import="_format_import", format_call="_format_call")

But this does not work apparently:

ERROR: [snip]/internal/gazelle_binary_test.bzl:2:44: symbol '_format_call' is private and cannot be imported
ERROR: [snip]/internal/gazelle_binary_test.bzl:2:76: symbol '_format_import' is private and cannot be imported

If there is a way to import private functions, I would prefer it. If not I made the functions importable in these changes. I understand the files are in the internal directory already, so their "repo-local" nature is already encoded.

[achew22]

I did a little sleuthing and I don't think that it's possible to do that. Fortunately, these functions live in internal so they are not importable to an external party, they would have to explicitly be imported and reexported by something outside that directory so I don't think the visibility of this is being significantly increased and I don't want to block rules_python being imported just because of this.

Thanks so much for your contribution!