Restore compatibility with Go 1.18

BUILD.bazel

@@ -1,6 +1,6 @@
 load("@bazel_gazelle_is_bazel_module//:defs.bzl", "GAZELLE_IS_BAZEL_MODULE")
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
-load("@io_bazel_rules_go//go:def.bzl", "nogo")
+load("@io_bazel_rules_go//go:def.bzl", "go_cross_binary", "nogo")
 load("//:def.bzl", "gazelle", "gazelle_binary")
 
 # gazelle:prefix github.com/bazelbuild/bazel-gazelle
@@ -38,6 +38,12 @@ gazelle_binary(
  ],
 )
 
+go_cross_binary(
+ name = "gazelle_local_go1.18",
+ sdk_version = "1.18",
+ target = ":gazelle_local",
+)
+
 nogo(
  name = "nogo",
  vet = True,

MODULE.bazel

@@ -58,6 +58,10 @@ bazel_dep(name = "bazel_skylib_gazelle_plugin", version = "1.4.1", dev_dependenc
 bazel_dep(name = "stardoc", version = "0.6.2", dev_dependency = True, repo_name = "io_bazel_stardoc")
 
 go_sdk_dev = use_extension("@io_bazel_rules_go//go:extensions.bzl", "go_sdk", dev_dependency = True)
+go_sdk_dev.download(version = "1.22.4")
+
+# Used by compatibility tests, keep as low as possible.
+go_sdk_dev.download(version = "1.18.10")
 
 # Known to exist since it is instantiated by rules_go itself.
 use_repo(

WORKSPACE

@@ -34,7 +34,7 @@ load("@bazel_features//:deps.bzl", "bazel_features_deps")
 
 bazel_features_deps()
 
-load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
+load("@io_bazel_rules_go//go:deps.bzl", "go_download_sdk", "go_register_toolchains", "go_rules_dependencies")
 
 go_rules_dependencies()
 
@@ -43,9 +43,14 @@ go_register_toolchains(
  version = "1.22.0",
 )
 
+go_download_sdk(
+ name = "go_compat_sdk",
+ version = "1.18.10",
+)
+
 load("//:deps.bzl", "gazelle_dependencies")
 
-gazelle_dependencies()
+gazelle_dependencies(go_sdk = "go_sdk")
 
 # For API doc generation
 # This is a dev dependency, users should not need to install it

cmd/fetch_repo/BUILD.bazel

@@ -1,10 +1,11 @@
-load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library", "go_test")
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_cross_binary", "go_library", "go_test")
 
 go_library(
  name = "fetch_repo_lib",
  srcs = [
  "clean.go",
  "copy_tree.go",
+ "errorscompat.go",
  "fetch_repo.go",
  "go_mod_download.go",
  "module.go",
@@ -25,6 +26,13 @@ go_binary(
  visibility = ["//visibility:public"],
 )
 
+# Verify that fetch_repo builds with Go 1.18.
+go_cross_binary(
+ name = "fetch_repo_go1.18",
+ sdk_version = "1.18",
+ target = ":fetch_repo",
+)
+
 go_test(
  name = "fetch_repo_test",
  srcs = ["fetch_repo_test.go"],
@@ -39,6 +47,7 @@ filegroup(
  "BUILD.bazel",
  "clean.go",
  "copy_tree.go",
+ "errorscompat.go",
  "fetch_repo.go",
  "fetch_repo_test.go",
  "go_mod_download.go",

cmd/fetch_repo/errorscompat.go

@@ -0,0 +1,61 @@
+// Taken from
+// https://github.com/golang/go/blob/20b79fd5775c39061d949569743912ad5e58b0e7/src/errors/join.go
+// TODO: Remove when Go 1.20 is the minimum supported version.
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+// Join returns an error that wraps the given errors.
+// Any nil error values are discarded.
+// Join returns nil if every value in errs is nil.
+// The error formats as the concatenation of the strings obtained
+// by calling the Error method of each element of errs, with a newline
+// between each string.
+//
+// A non-nil error returned by Join implements the Unwrap() []error method.
+func Join(errs ...error) error {
+ n := 0
+ for _, err := range errs {
+ if err != nil {
+ n++
+ }
+ }
+ if n == 0 {
+ return nil
+ }
+ e := &joinError{
+ errs: make([]error, 0, n),
+ }
+ for _, err := range errs {
+ if err != nil {
+ e.errs = append(e.errs, err)
+ }
+ }
+ return e
+}
+
+type joinError struct {
+ errs []error
+}
+
+func (e *joinError) Error() string {
+ // Since Join returns nil if every value in errs is nil,
+ // e.errs cannot be empty.
+ if len(e.errs) == 1 {
+ return e.errs[0].Error()
+ }
+
+ b := []byte(e.errs[0].Error())
+ for _, err := range e.errs[1:] {
+ b = append(b, '\n')
+ b = append(b, err.Error()...)
+ }
+ return string(b)
+}
+
+func (e *joinError) Unwrap() []error {
+ return e.errs
+}

cmd/fetch_repo/go_mod_download.go

@@ -61,7 +61,7 @@ func runGoModDownload(dl *GoModDownloadResult, dest string, importpath string, v
  return fmt.Errorf("go mod download output format: `%s %s`: parsing JSON: %q error: %w", cmd.Path, strings.Join(cmd.Args, " "), buf.String(), err)
  }
  if dl.Error != "" {
- return errors.Join(errors.New(dl.Error), dlErr)
+ return Join(errors.New(dl.Error), dlErr)
  }
  if dlErr != nil {
  return dlErr

go.mod

@@ -1,6 +1,6 @@
 module github.com/bazelbuild/bazel-gazelle
 
-go 1.21.4
+go 1.21
 
 require (
  github.com/bazelbuild/buildtools v0.0.0-20240313121412-66c605173954

internal/go_repository_tools_srcs.bzl

@@ -10,6 +10,7 @@ GO_REPOSITORY_TOOLS_SRCS = [
  Label("//cmd/fetch_repo:BUILD.bazel"),
  Label("//cmd/fetch_repo:clean.go"),
  Label("//cmd/fetch_repo:copy_tree.go"),
+ Label("//cmd/fetch_repo:errorscompat.go"),
  Label("//cmd/fetch_repo:fetch_repo.go"),
  Label("//cmd/fetch_repo:go_mod_download.go"),
  Label("//cmd/fetch_repo:module.go"),