fix(releaser): add MODULE.bazel boilerplate

go/tools/releaser/BUILD.bazel

@@ -31,7 +31,11 @@ go_library(
 
 go_test(
     name = "releaser_test",
-    srcs = ["upgradedep_test.go"],
+    srcs = [
+        "boilerplate_test.go",
+        "upgradedep_test.go",
+    ],
+    data = glob(["testdata/**"]),
     embed = [":releaser_lib"],
     deps = ["@com_github_bazelbuild_buildtools//build:go_default_library"],
 )

go/tools/releaser/boilerplate.go

@@ -21,27 +21,44 @@ import (
 	"io"
 	"net/http"
 	"sort"
+	"strings"
 
 	"golang.org/x/mod/semver"
 )
 
-func genBoilerplate(version, shasum, goVersion string) string {
-	return fmt.Sprintf(`load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+func genBoilerplate(version, shasum, goVersion, rnotesData string) string {
+	trimmedVersion := strings.TrimPrefix(version, "v")
+	return fmt.Sprintf(`%[4]s
+
+## `+"`MODULE.bazel`"+` code
+
+`+"```"+`
+bazel_dep(name = "rules_go", version = "%[1]s")
+
+go_sdk = use_extension("@rules_go//go:extensions.bzl", "go_sdk")
+go_sdk.download(version = "%[3]s")
+`+"```"+`
+
+## `+"`WORKSPACE`"+` code
+
+`+"```"+`
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 http_archive(
     name = "io_bazel_rules_go",
     sha256 = "%[2]s",
     urls = [
-        "https://mirror.bazel.build/github.com/bazel-contrib/rules_go/releases/download/%[1]s/rules_go-%[1]s.zip",
-        "https://github.com/bazel-contrib/rules_go/releases/download/%[1]s/rules_go-%[1]s.zip",
+        "https://mirror.bazel.build/github.com/bazel-contrib/rules_go/releases/download/v%[1]s/rules_go-v%[1]s.zip",
+        "https://github.com/bazel-contrib/rules_go/releases/download/v%[1]s/rules_go-v%[1]s.zip",
     ],
 )
 
 load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
 
 go_rules_dependencies()
 
-go_register_toolchains(version = "%[3]s")`, version, shasum, goVersion)
+go_register_toolchains(version = "%[3]s")
+`+"```\n", trimmedVersion, shasum, goVersion, rnotesData)
 }
 
 func findLatestGoVersion() (v string, err error) {

go/tools/releaser/boilerplate_test.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestGenBoilerplate(t *testing.T) {
+	version := "v1.2.3"
+	shasum := "abcd1234"
+	goVersion := "1.23"
+	rnotesData := "Release notes"
+
+	actual := genBoilerplate(version, shasum, goVersion, rnotesData)
+
+	expectedPath := filepath.Join(".", "testdata", "boilerplate.md")
+	expectedBytes, err := os.ReadFile(expectedPath)
+	if err != nil {
+		t.Fatalf("failed to read expected boilerplate: %v", err)
+	}
+	expected := strings.TrimSpace(string(expectedBytes))
+	actual = strings.TrimSpace(actual)
+
+	if actual != expected {
+		t.Errorf("generated boilerplate does not match expected\nExpected:\n%s\nActual:\n%s", expected, actual)
+	}
+}

go/tools/releaser/prepare.go

@@ -159,8 +159,7 @@ func runPrepare(ctx context.Context, stderr io.Writer, args []string) error {
 	if err != nil {
 		return err
 	}
-	boilerplate := genBoilerplate(version, arcSum, goVersion)
-	rnotesStr := string(rnotesData) + "\n\n## `WORKSPACE` code\n\n```\n" + boilerplate + "\n```\n"
+	rnotesStr := genBoilerplate(version, arcSum, goVersion, string(rnotesData))
 
 	// Push the release branch.
 	fmt.Fprintf(stderr, "pushing branch %s to origin...\n", branchName)

go/tools/releaser/testdata/boilerplate.md

@@ -0,0 +1,31 @@
+Release notes
+
+## `MODULE.bazel` code
+
+```
+bazel_dep(name = "rules_go", version = "1.2.3")
+
+go_sdk = use_extension("@rules_go//go:extensions.bzl", "go_sdk")
+go_sdk.download(version = "1.23")
+```
+
+## `WORKSPACE` code
+
+```
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "io_bazel_rules_go",
+    sha256 = "abcd1234",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazel-contrib/rules_go/releases/download/v1.2.3/rules_go-v1.2.3.zip",
+        "https://github.com/bazel-contrib/rules_go/releases/download/v1.2.3/rules_go-v1.2.3.zip",
+    ],
+)
+
+load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
+
+go_rules_dependencies()
+
+go_register_toolchains(version = "1.23")
+```