[ruby/rubygems] Add `--ext=go` to `bundle gem`

(https://github.com/ruby/rubygems/pull/8183)

* Add new gem templates

* Add `--ext=go` in `bundle gem`

* Add setup-go to .github/workflows/main.yml

* Embed go version in go.mod

* Use go in bundler CI

* Add example method to template

* Install Go in .circleci/config.yml

* Install Go in .gitlab-ci.yml

* Allow hard tabs in go template

* Run `rake update_manifest`

* Fix test

* Move go_gem to gemspec

Respect to 9b0ec80

* nits: :golf:

* includes valid module name in go.mod

* generate header file

* Run `go mod tidy` to create `go.sum`

* Check if `go.sum` is generated only when Go is installed

To avoid test failure in environments where Go is not installed

* Run CI

* Workaround for hung up

c.f. https://github.com/rubygems/rubygems/actions/runs/11639408044/job/32415545422

* Write man for --ext=go

* Re-generate man with `./bin/rake man:build`

* pinning :pushpin:

* Update with `./bin/rake man:build`

* nits: Extract to method

* nits: Use `sys_exec` instead of `system`

* Clean go module cache after test

Workaround following error

```
1) bundle gem gem naming with underscore --ext parameter set with go includes go_gem extension in extconf.rb
   Failure/Error: FileUtils.rm_r(dir)

   Errno::EACCES:
     Permission denied @ apply2files - /home/runner/work/rubygems/rubygems/bundler/tmp/2.2/home/go/pkg/mod/gopkg.in/yaml.v3@v3.0.1/decode_test.go
   # ./spec/support/helpers.rb:37:in `block in reset!'
   # ./spec/support/helpers.rb:21:in `each'
   # ./spec/support/helpers.rb:21:in `reset!'
   # ./spec/spec_helper.rb:130:in `block (2 levels) in <top (required)>'
   # /home/runner/work/rubygems/rubygems/lib/rubygems.rb:303:in `load'
   # /home/runner/work/rubygems/rubygems/lib/rubygems.rb:303:in `activate_and_load_bin_path'
```

Files installed with `go get` have permissions set to 444
ref. https://github.com/golang/go/issues/35615

```
$ ls -l /home/runner/work/rubygems/rubygems/bundler/tmp/2.2/home/go/pkg/mod/gopkg.in/yaml.v3@v3.0.1/decode_test.go
-r--r--r-- 1 runner runner 42320 Nov 15 06:38 /home/runner/work/rubygems/rubygems/bundler/tmp/2.2/home/go/pkg/mod/gopkg.in/yaml.v3@v3.0.1/decode_test.go
```

So they cannot be deleted by `FileUtils.rm_r`.
Therefore, this is necessary to execute `go clean -modcache` separately from `FileUtils.rm_r` to circumvent it.

* Remove needless changes

ref. https://github.com/ruby/rubygems/pull/8183#discussion_r2532902051

* ci: setup-go is needless

* Don't run go command in `bundle gem`

ref. https://github.com/ruby/rubygems/pull/8183#discussion_r2532765470

* Revert unrelated date changes

---------

https://github.com/ruby/rubygems/commit/260d7d60b3

Co-authored-by: Hiroshi SHIBATA <hsbt@ruby-lang.org>

14 files changed, 254 insertions, 7 deletions

diff --git a/lib/bundler/cli.rb b/lib/bundler/cli.rb
index af634291dd..86b86b359f 100644
--- a/lib/bundler/cli.rb
+++ b/lib/bundler/cli.rb
@@ -11,7 +11,7 @@ module Bundler
 
     AUTO_INSTALL_CMDS = %w[show binstubs outdated exec open console licenses clean].freeze
     PARSEABLE_COMMANDS = %w[check config help exec platform show version].freeze
-    EXTENSIONS = ["c", "rust"].freeze
+    EXTENSIONS = ["c", "rust", "go"].freeze
 
     COMMAND_ALIASES = {
       "check" => "c",
diff --git a/lib/bundler/cli/gem.rb b/lib/bundler/cli/gem.rb
index abfb095d46..236ce530ec 100644
--- a/lib/bundler/cli/gem.rb
+++ b/lib/bundler/cli/gem.rb
@@ -13,6 +13,8 @@ module Bundler
       "test-unit" => "3.0",
     }.freeze
 
+    DEFAULT_GITHUB_USERNAME = "[USERNAME]"
+
     attr_reader :options, :gem_name, :thor, :name, :target, :extension
 
     def initialize(options, gem_name, thor)
@@ -72,7 +74,7 @@ module Bundler
         bundle: options[:bundle],
         bundler_version: bundler_dependency_version,
         git: use_git,
-        github_username: github_username.empty? ? "[USERNAME]" : github_username,
+        github_username: github_username.empty? ? DEFAULT_GITHUB_USERNAME : github_username,
         required_ruby_version: required_ruby_version,
         rust_builder_required_rubygems_version: rust_builder_required_rubygems_version,
         minitest_constant_name: minitest_constant_name,
@@ -231,6 +233,18 @@ module Bundler
         )
       end
 
+      if extension == "go"
+        templates.merge!(
+          "ext/newgem/go.mod.tt" => "ext/#{name}/go.mod",
+          "ext/newgem/extconf-go.rb.tt" => "ext/#{name}/extconf.rb",
+          "ext/newgem/newgem.h.tt" => "ext/#{name}/#{underscored_name}.h",
+          "ext/newgem/newgem.go.tt" => "ext/#{name}/#{underscored_name}.go",
+          "ext/newgem/newgem-go.c.tt" => "ext/#{name}/#{underscored_name}.c",
+        )
+
+        config[:go_module_username] = config[:github_username] == DEFAULT_GITHUB_USERNAME ? "username" : config[:github_username]
+      end
+
       if target.exist? && !target.directory?
         Bundler.ui.error "Couldn't create a new gem named `#{gem_name}` because there's an existing file named `#{gem_name}`."
         exit Bundler::BundlerError.all_errors[Bundler::GenericSystemCallError]
diff --git a/lib/bundler/man/bundle-gem.1 b/lib/bundler/man/bundle-gem.1
index 670a69d67e..85c0f57674 100644
--- a/lib/bundler/man/bundle-gem.1
+++ b/lib/bundler/man/bundle-gem.1
@@ -38,8 +38,8 @@ Add a \fBCHANGELOG\.md\fR file to the root of the generated project\. If this op
 \fB\-\-no\-changelog\fR
 Do not create a \fBCHANGELOG\.md\fR (overrides \fB\-\-changelog\fR specified in the global config)\.
 .TP
-\fB\-\-ext=c\fR, \fB\-\-ext=rust\fR
-Add boilerplate for C or Rust (currently magnus \fIhttps://docs\.rs/magnus\fR based) extension code to the generated project\. This behavior is disabled by default\.
+\fB\-\-ext=c\fR, \fB\-\-ext=go\fR, \fB\-\-ext=rust\fR
+Add boilerplate for C, Go (currently go\-gem\-wrapper \fIhttps://github\.com/ruby\-go\-gem/go\-gem\-wrapper\fR based) or Rust (currently magnus \fIhttps://docs\.rs/magnus\fR based) extension code to the generated project\. This behavior is disabled by default\.
 .TP
 \fB\-\-no\-ext\fR
 Do not add extension code (overrides \fB\-\-ext\fR specified in the global config)\.
diff --git a/lib/bundler/man/bundle-gem.1.ronn b/lib/bundler/man/bundle-gem.1.ronn
index b71bde9f65..488c8113e4 100644
--- a/lib/bundler/man/bundle-gem.1.ronn
+++ b/lib/bundler/man/bundle-gem.1.ronn
@@ -51,8 +51,8 @@ configuration file using the following names:
   Do not create a `CHANGELOG.md` (overrides `--changelog` specified in the
   global config).
 
-* `--ext=c`, `--ext=rust`:
-  Add boilerplate for C or Rust (currently [magnus](https://docs.rs/magnus) based) extension code to the generated project. This behavior
+* `--ext=c`, `--ext=go`, `--ext=rust`:
+  Add boilerplate for C, Go (currently [go-gem-wrapper](https://github.com/ruby-go-gem/go-gem-wrapper) based) or Rust (currently [magnus](https://docs.rs/magnus) based) extension code to the generated project. This behavior
   is disabled by default.
 
 * `--no-ext`:
diff --git a/lib/bundler/templates/newgem/circleci/config.yml.tt b/lib/bundler/templates/newgem/circleci/config.yml.tt
index f40f029bf1..c4dd9d0647 100644
--- a/lib/bundler/templates/newgem/circleci/config.yml.tt
+++ b/lib/bundler/templates/newgem/circleci/config.yml.tt
@@ -7,6 +7,10 @@ jobs:
     environment:
       RB_SYS_FORCE_INSTALL_RUST_TOOLCHAIN: 'true'
 <%- end -%>
+<%- if config[:ext] == 'go' -%>
+    environment:
+      GO_VERSION: '1.23.0'
+<%- end -%>
     steps:
       - checkout
 <%- if config[:ext] == 'rust' -%>
@@ -17,6 +21,14 @@ jobs:
           name: Install a RubyGems version that can compile rust extensions
           command: gem update --system '<%= ::Gem.rubygems_version %>'
 <%- end -%>
+<%- if config[:ext] == 'go' -%>
+      - run:
+          name: Install Go
+          command: |
+            wget https://go.dev/dl/go$GO_VERSION.linux-amd64.tar.gz -O /tmp/go.tar.gz
+            tar -C /usr/local -xzf /tmp/go.tar.gz
+            echo 'export PATH=/usr/local/go/bin:"$PATH"' >> "$BASH_ENV"
+<%- end -%>
       - run:
           name: Run the default task
           command: |
diff --git a/lib/bundler/templates/newgem/ext/newgem/extconf-go.rb.tt b/lib/bundler/templates/newgem/ext/newgem/extconf-go.rb.tt
new file mode 100644
index 0000000000..a689e21ebe
--- /dev/null
+++ b/lib/bundler/templates/newgem/ext/newgem/extconf-go.rb.tt
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require "mkmf"
+require "go_gem/mkmf"
+
+# Makes all symbols private by default to avoid unintended conflict
+# with other gems. To explicitly export symbols you can use RUBY_FUNC_EXPORTED
+# selectively, or entirely remove this flag.
+append_cflags("-fvisibility=hidden")
+
+create_go_makefile(<%= config[:makefile_path].inspect %>)
diff --git a/lib/bundler/templates/newgem/ext/newgem/go.mod.tt b/lib/bundler/templates/newgem/ext/newgem/go.mod.tt
new file mode 100644
index 0000000000..3f4819d004
--- /dev/null
+++ b/lib/bundler/templates/newgem/ext/newgem/go.mod.tt
@@ -0,0 +1,5 @@
+module github.com/<%= config[:go_module_username] %>/<%= config[:underscored_name] %>
+
+go 1.23
+
+require github.com/ruby-go-gem/go-gem-wrapper latest
diff --git a/lib/bundler/templates/newgem/ext/newgem/newgem-go.c.tt b/lib/bundler/templates/newgem/ext/newgem/newgem-go.c.tt
new file mode 100644
index 0000000000..119c0c96ea
--- /dev/null
+++ b/lib/bundler/templates/newgem/ext/newgem/newgem-go.c.tt
@@ -0,0 +1,2 @@
+#include "<%= config[:underscored_name] %>.h"
+#include "_cgo_export.h"
diff --git a/lib/bundler/templates/newgem/ext/newgem/newgem.go.tt b/lib/bundler/templates/newgem/ext/newgem/newgem.go.tt
new file mode 100644
index 0000000000..f19b750e58
--- /dev/null
+++ b/lib/bundler/templates/newgem/ext/newgem/newgem.go.tt
@@ -0,0 +1,31 @@
+package main
+
+/*
+#include "<%= config[:underscored_name] %>.h"
+
+VALUE rb_<%= config[:underscored_name] %>_sum(VALUE self, VALUE a, VALUE b);
+*/
+import "C"
+
+import (
+	"github.com/ruby-go-gem/go-gem-wrapper/ruby"
+)
+
+//export rb_<%= config[:underscored_name] %>_sum
+func rb_<%= config[:underscored_name] %>_sum(_ C.VALUE, a C.VALUE, b C.VALUE) C.VALUE {
+	longA := ruby.NUM2LONG(ruby.VALUE(a))
+	longB := ruby.NUM2LONG(ruby.VALUE(b))
+
+	sum := longA + longB
+
+	return C.VALUE(ruby.LONG2NUM(sum))
+}
+
+//export Init_<%= config[:underscored_name] %>
+func Init_<%= config[:underscored_name] %>() {
+	rb_m<%= config[:constant_array].join %> := ruby.RbDefineModule(<%= config[:constant_name].inspect %>)
+	ruby.RbDefineSingletonMethod(rb_m<%= config[:constant_array].join %>, "sum", C.rb_<%= config[:underscored_name] %>_sum, 2)
+}
+
+func main() {
+}
diff --git a/lib/bundler/templates/newgem/github/workflows/main.yml.tt b/lib/bundler/templates/newgem/github/workflows/main.yml.tt
index 9224ee0ca2..7f3e3a5b66 100644
--- a/lib/bundler/templates/newgem/github/workflows/main.yml.tt
+++ b/lib/bundler/templates/newgem/github/workflows/main.yml.tt
@@ -35,5 +35,11 @@ jobs:
           ruby-version: ${{ matrix.ruby }}
           bundler-cache: true
 <%- end -%>
+<%- if config[:ext] == 'go' -%>
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: ext/<%= config[:underscored_name] %>/go.mod
+<%- end -%>
       - name: Run the default task
         run: bundle exec rake
diff --git a/lib/bundler/templates/newgem/gitlab-ci.yml.tt b/lib/bundler/templates/newgem/gitlab-ci.yml.tt
index d2e1f33736..adbd70cbc0 100644
--- a/lib/bundler/templates/newgem/gitlab-ci.yml.tt
+++ b/lib/bundler/templates/newgem/gitlab-ci.yml.tt
@@ -6,6 +6,11 @@ default:
     - apt-get update && apt-get install -y clang
     - gem update --system '<%= ::Gem.rubygems_version %>'
 <%- end -%>
+<%- if config[:ext] == 'go' -%>
+    - wget https://go.dev/dl/go$GO_VERSION.linux-amd64.tar.gz -O /tmp/go.tar.gz
+    - tar -C /usr/local -xzf /tmp/go.tar.gz
+    - export PATH=/usr/local/go/bin:$PATH
+<%- end -%>
     - gem install bundler -v <%= Bundler::VERSION %>
     - bundle install
 
@@ -14,5 +19,9 @@ example_job:
   variables:
     RB_SYS_FORCE_INSTALL_RUST_TOOLCHAIN: 'true'
 <%- end -%>
+<%- if config[:ext] == 'go' -%>
+  variables:
+    GO_VERSION: '1.23.0'
+<%- end -%>
   script:
     - bundle exec rake
diff --git a/lib/bundler/templates/newgem/newgem.gemspec.tt b/lib/bundler/templates/newgem/newgem.gemspec.tt
index c87abda8a0..513875fd63 100644
--- a/lib/bundler/templates/newgem/newgem.gemspec.tt
+++ b/lib/bundler/templates/newgem/newgem.gemspec.tt
@@ -38,7 +38,7 @@ Gem::Specification.new do |spec|
   spec.bindir = "exe"
   spec.executables = spec.files.grep(%r{\Aexe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
-<%- if config[:ext] == 'c' || config[:ext] == 'rust' -%>
+<%- if %w(c rust go).include?(config[:ext]) -%>
   spec.extensions = ["ext/<%= config[:underscored_name] %>/extconf.rb"]
 <%- end -%>
 
@@ -47,6 +47,9 @@ Gem::Specification.new do |spec|
 <%- if config[:ext] == 'rust' -%>
   spec.add_dependency "rb_sys", "~> 0.9.91"
 <%- end -%>
+<%- if config[:ext] == 'go' -%>
+  spec.add_dependency "go_gem", "~> 0.2"
+<%- end -%>
 
   # For more information and examples about making a new gem, check out our
   # guide at: https://bundler.io/guides/creating_gem.html
diff --git a/spec/bundler/commands/newgem_spec.rb b/spec/bundler/commands/newgem_spec.rb
index 1ce4a0da09..7a837bd08f 100644
--- a/spec/bundler/commands/newgem_spec.rb
+++ b/spec/bundler/commands/newgem_spec.rb
@@ -31,6 +31,13 @@ RSpec.describe "bundle gem" do
     matched[:ignored]&.split(" ")
   end
 
+  def installed_go?
+    sys_exec("go version", raise_on_error: true)
+    true
+  rescue StandardError
+    false
+  end
+
   let(:generated_gemspec) { Bundler.load_gemspec_uncached(bundled_app(gem_name).join("#{gem_name}.gemspec")) }
 
   let(:gem_name) { "mygem" }
@@ -1748,6 +1755,150 @@ RSpec.describe "bundle gem" do
         expect(bundled_app("#{gem_name}/Rakefile").read).to eq(rakefile)
       end
     end
+
+    context "--ext parameter set with go" do
+      let(:flags) { "--ext=go" }
+
+      before do
+        bundle ["gem", gem_name, flags].compact.join(" ")
+      end
+
+      after do
+        sys_exec("go clean -modcache", raise_on_error: true) if installed_go?
+      end
+
+      it "is not deprecated" do
+        expect(err).not_to include "[DEPRECATED] Option `--ext` without explicit value is deprecated."
+      end
+
+      it "builds ext skeleton" do
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/#{gem_name}.c")).to exist
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/#{gem_name}.go")).to exist
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/#{gem_name}.h")).to exist
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/extconf.rb")).to exist
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/go.mod")).to exist
+      end
+
+      it "includes extconf.rb in gem_name.gemspec" do
+        expect(bundled_app("#{gem_name}/#{gem_name}.gemspec").read).to include(%(spec.extensions = ["ext/#{gem_name}/extconf.rb"]))
+      end
+
+      it "includes go_gem in gem_name.gemspec" do
+        expect(bundled_app("#{gem_name}/#{gem_name}.gemspec").read).to include('spec.add_dependency "go_gem", "~> 0.2"')
+      end
+
+      it "includes go_gem extension in extconf.rb" do
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/extconf.rb").read).to include(<<~RUBY)
+          require "mkmf"
+          require "go_gem/mkmf"
+        RUBY
+
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/extconf.rb").read).to include(%(create_go_makefile("#{gem_name}/#{gem_name}")))
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/extconf.rb").read).not_to include("create_makefile")
+      end
+
+      it "includes go_gem extension in gem_name.c" do
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/#{gem_name}.c").read).to eq(<<~C)
+          #include "#{gem_name}.h"
+          #include "_cgo_export.h"
+        C
+      end
+
+      it "includes skeleton code in gem_name.go" do
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/#{gem_name}.go").read).to include(<<~GO)
+          /*
+          #include "#{gem_name}.h"
+
+          VALUE rb_#{gem_name}_sum(VALUE self, VALUE a, VALUE b);
+          */
+          import "C"
+        GO
+
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/#{gem_name}.go").read).to include(<<~GO)
+          //export rb_#{gem_name}_sum
+          func rb_#{gem_name}_sum(_ C.VALUE, a C.VALUE, b C.VALUE) C.VALUE {
+        GO
+
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/#{gem_name}.go").read).to include(<<~GO)
+          //export Init_#{gem_name}
+          func Init_#{gem_name}() {
+        GO
+      end
+
+      it "includes valid module name in go.mod" do
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/go.mod").read).to include("module github.com/bundleuser/#{gem_name}")
+      end
+
+      context "with --no-ci" do
+        let(:flags) { "--ext=go --no-ci" }
+
+        it_behaves_like "CI config is absent"
+      end
+
+      context "--ci set to github" do
+        let(:flags) { "--ext=go --ci=github" }
+
+        it "generates .github/workflows/main.yml" do
+          expect(bundled_app("#{gem_name}/.github/workflows/main.yml")).to exist
+          expect(bundled_app("#{gem_name}/.github/workflows/main.yml").read).to include("go-version-file: ext/#{gem_name}/go.mod")
+        end
+      end
+
+      context "--ci set to circle" do
+        let(:flags) { "--ext=go --ci=circle" }
+
+        it "generates a .circleci/config.yml" do
+          expect(bundled_app("#{gem_name}/.circleci/config.yml")).to exist
+
+          expect(bundled_app("#{gem_name}/.circleci/config.yml").read).to include(<<-YAML.strip)
+    environment:
+      GO_VERSION:
+          YAML
+
+          expect(bundled_app("#{gem_name}/.circleci/config.yml").read).to include(<<-YAML)
+      - run:
+          name: Install Go
+          command: |
+            wget https://go.dev/dl/go$GO_VERSION.linux-amd64.tar.gz -O /tmp/go.tar.gz
+            tar -C /usr/local -xzf /tmp/go.tar.gz
+            echo 'export PATH=/usr/local/go/bin:"$PATH"' >> "$BASH_ENV"
+          YAML
+        end
+      end
+
+      context "--ci set to gitlab" do
+        let(:flags) { "--ext=go --ci=gitlab" }
+
+        it "generates a .gitlab-ci.yml" do
+          expect(bundled_app("#{gem_name}/.gitlab-ci.yml")).to exist
+
+          expect(bundled_app("#{gem_name}/.gitlab-ci.yml").read).to include(<<-YAML)
+    - wget https://go.dev/dl/go$GO_VERSION.linux-amd64.tar.gz -O /tmp/go.tar.gz
+    - tar -C /usr/local -xzf /tmp/go.tar.gz
+    - export PATH=/usr/local/go/bin:$PATH
+          YAML
+
+          expect(bundled_app("#{gem_name}/.gitlab-ci.yml").read).to include(<<-YAML.strip)
+  variables:
+    GO_VERSION:
+          YAML
+        end
+      end
+
+      context "without github.user" do
+        before do
+          # FIXME: GitHub Actions Windows Runner hang up here for some reason...
+          skip "Workaround for hung up" if Gem.win_platform?
+
+          git("config --global --unset github.user")
+          bundle ["gem", gem_name, flags].compact.join(" ")
+        end
+
+        it "includes valid module name in go.mod" do
+          expect(bundled_app("#{gem_name}/ext/#{gem_name}/go.mod").read).to include("module github.com/username/#{gem_name}")
+        end
+      end
+    end
   end
 
   context "gem naming with dashed" do
diff --git a/spec/bundler/quality_spec.rb b/spec/bundler/quality_spec.rb
index bbd6517f21..b60be9980f 100644
--- a/spec/bundler/quality_spec.rb
+++ b/spec/bundler/quality_spec.rb
@@ -20,6 +20,9 @@ RSpec.describe "The library itself" do
   end
 
   def check_for_tab_characters(filename)
+    # Because Go uses hard tabs
+    return if filename.end_with?(".go.tt")
+
     failing_lines = []
     each_line(filename) do |line, number|
       failing_lines << number + 1 if line.include?("\t")