Port test_warn_zeitwerk.rb to RSpec example

Merged: https://github.com/ruby/ruby/pull/12098

spec/bundler/bundled_gems_spec.rb

@@ -223,6 +223,25 @@ RSpec.describe "bundled_gems.rb" do
     # $GEM_HOME/gems/childprocess-5.0.0/lib/childprocess.rb:7: warning:
   end
 
+  it "Show warning with zeitwerk" do
+    libpath = Dir[Spec::Path.base_system_gem_path.join("gems/{zeitwerk}-*/lib")].map(&:to_s).first
+    code = <<-RUBY
+      $LOAD_PATH.unshift("#{libpath}")
+      require "zeitwerk"
+      loader = Zeitwerk::Loader.for_gem(warn_on_extra_files: false)
+      loader.setup
+
+      require 'ostruct'
+    RUBY
+    create_file("script.rb", code)
+    create_file("Gemfile", "source 'https://rubygems.org'")
+    bundle "exec ruby script.rb"
+
+    expect(err).to include(/ostruct was loaded from (.*) from Ruby 3.5.0/)
+    # TODO: We should assert caller location like below:
+    # test_warn_zeitwerk.rb:15: warning: ...
+  end
+
   it "Don't show warning fiddle/import when fiddle on Gemfile" do
     build_lib "fiddle", "1.0.0" do |s|
       s.write "lib/fiddle.rb", "puts 'fiddle'"

tool/bundler/test_gems.rb

@@ -13,3 +13,6 @@ gem "rake", "~> 13.1"
 gem "builder", "~> 3.2"
 gem "rb_sys"
 gem "rubygems-generate_index", "~> 1.1"
+
+# for bundled_gems_spec.rb
+gem "zeitwerk", "~> 2.7"

tool/test_for_warn_bundled_gems/.gitignore

@@ -1 +0,0 @@
-tmp

tool/test_for_warn_bundled_gems/README.md

@@ -1,3 +0,0 @@
-This directory contains tests for the bundled gems warning under the Bundler.
-
-see [test.sh](./test.sh) for details.

tool/test_for_warn_bundled_gems/test.sh

@@ -1,5 +0,0 @@
-#!/bin/bash
-
-echo "* Show warning with zeitwerk"
-ruby test_warn_zeitwerk.rb
-echo

tool/test_for_warn_bundled_gems/test_warn_zeitwerk.rb

@@ -1,15 +0,0 @@
-require "bundler"
-Bundler::Definition.no_lock = true
-
-require "bundler/inline"
-
-gemfile do
-  source "https://rubygems.org"
-  gem "zeitwerk", require: false
-end
-
-require "zeitwerk"
-loader = Zeitwerk::Loader.for_gem(warn_on_extra_files: false)
-loader.setup
-
-require 'csv'