bzlmod: Fix repo name used by gopackagesdriver (#3516)

* Reference `rulesGoRepositoryName` (sourced from environment variable) instead of hard-coding `@io_bazel_rules_go` repo name.

* gopackagesdriver: Inject rules_go repo name via x_defs

This ensures that we always specify the correct repo name when invoking
the aspect, even with Bzlmod (where users usually refer to rules_go as
`@rules_go`, not `@io_bazel_rules_go`, but could choose any apparent
repository name for it).

---------

Co-authored-by: Brice <[email protected]>

go/tools/gopackagesdriver/BUILD.bazel

@@ -1,4 +1,5 @@
 load("//go:def.bzl", "go_binary", "go_library")
+load(":aspect.bzl", "bazel_supports_canonical_label_literals")
 
 go_library(
     name = "gopackagesdriver_lib",
@@ -20,5 +21,19 @@ go_library(
 go_binary(
     name = "gopackagesdriver",
     embed = [":gopackagesdriver_lib"],
+    x_defs = {
+        # Determine the name of the rules_go repository as we need to specify it when invoking the
+        # aspect.
+        # If canonical label literals are supported, we can use a canonical label literal (starting
+        # with @@) to pass the repository_name() through repo mapping unchanged.
+        # If canonical label literals are not supported, then bzlmod is certainly not enabled and
+        # we can assume that the repository name is not affected by repo mappings.
+        # If run in the rules_go repo itself, repository_name() returns "@", which is equivalent to
+        # "@io_bazel_rules_go" since Bazel 6:
+        # https://github.com/bazelbuild/bazel/commit/7694cf75e6366b92e3905c2ad60234cda57627ee
+        # TODO: Once we drop support for Bazel 5, we can remove the feature detection logic and
+        #       use "@" + repository_name().
+        "rulesGoRepositoryName": "@" + repository_name() if bazel_supports_canonical_label_literals() else repository_name(),
+    },
     visibility = ["//visibility:public"],
 )

go/tools/gopackagesdriver/aspect.bzl

@@ -34,6 +34,9 @@ PROTO_COMPILER_ATTRS = [
     "compilers",
 ]
 
+def bazel_supports_canonical_label_literals():
+    return str(Label("//:bogus")).startswith("@@")
+
 def is_file_external(f):
     return f.owner.workspace_root != ""
 

go/tools/gopackagesdriver/bazel_json_builder.go

@@ -31,9 +31,7 @@ type BazelJSONBuilder struct {
 	requests []string
 }
 
-const (
-	RulesGoStdlibLabel = "@io_bazel_rules_go//:stdlib"
-)
+var RulesGoStdlibLabel = rulesGoRepositoryName + "//:stdlib"
 
 var _defaultKinds = []string{"go_library", "go_test", "go_binary"}
 

go/tools/gopackagesdriver/main.go

@@ -49,9 +49,9 @@ type driverResponse struct {
 }
 
 var (
-	// It seems https://github.com/bazelbuild/bazel/issues/3115 isn't fixed when specifying
-	// the aspect from the command line. Use this trick in the mean time.
-	rulesGoRepositoryName = getenvDefault("GOPACKAGESDRIVER_RULES_GO_REPOSITORY_NAME", "@io_bazel_rules_go")
+	// Injected via x_defs.
+
+	rulesGoRepositoryName string
 	goDefaultAspect       = rulesGoRepositoryName + "//go/tools/gopackagesdriver:aspect.bzl%go_pkg_info_aspect"
 	bazelBin              = getenvDefault("GOPACKAGESDRIVER_BAZEL", "bazel")
 	bazelStartupFlags     = strings.Fields(os.Getenv("GOPACKAGESDRIVER_BAZEL_FLAGS"))

tools/gopackagesdriver.sh

@@ -1,3 +1,2 @@
 #!/usr/bin/env bash
-export GOPACKAGESDRIVER_RULES_GO_REPOSITORY_NAME=
 exec bazel run --tool_tag=gopackagesdriver -- //go/tools/gopackagesdriver "${@}"