Replace `with_rubygems` script

Instead, use a better rubygems version manager that makes sure that
`ENV["RGV"]` usage is always applied, and its usage is centralized at a
single place.

This simplifies the rake task organization and makes it much simpler to
run locally exactly what's run in CI. For example, since it doesn't rely
on the `RGV` being deleted for subsequent subprocesses, it also running
`bin/rake spec:travis` task locally which previously would lead to

```
rake aborted!

RubyGems version is required on Travis!
```

It also reduces duplication making it so that we only need to change the
`.travis.yml` file when updating tested rubies, and not the `Rakefile`
as well.

14 files changed, 132 insertions, 121 deletions

diff --git a/Rakefile b/Rakefile
index c41a6e9665..2935410628 100644
--- a/Rakefile
+++ b/Rakefile
@@ -85,80 +85,27 @@ namespace :spec do
     ENV["BUNDLER_SUDO_TESTS"] = "1"
   end
 
-  # RubyGems specs by version
-  namespace :rubygems do
-    # When editing this list, also edit .travis.yml!
-    branches = %w[master]
-    releases = %w[v2.5.2 v2.6.14 v2.7.10 v3.0.6]
-    (branches + releases).each do |rg|
-      desc "Run specs with RubyGems #{rg}"
-      task "parallel_#{rg}" do
-        sh("bin/parallel_rspec spec/")
-      end
-
-      task rg do
-        sh("bin/rspec --format progress")
-      end
-
-      # Create tasks like spec:rubygems:v1.8.3:sudo to run the sudo specs
-      namespace rg do
-        task :sudo => ["set_sudo", rg]
-        task :realworld => ["set_realworld", rg]
-      end
-
-      task "set_#{rg}" do
-        ENV["RGV"] = rg
-      end
-
-      task rg => ["set_#{rg}"]
-      task "rubygems:all" => rg
-    end
-
-    desc "Run specs under a RubyGems checkout (set RGV=path)"
-    task "co" do
-      sh("bin/parallel_rspec spec/")
-    end
-
-    namespace "co" do
-      task :sudo => ["set_sudo", "co"]
-      task :realworld => ["set_realworld", "co"]
-    end
-
-    task "setup_co" do
-      ENV["RGV"] = if `git -C "#{File.expand_path("..")}" remote --verbose 2> #{IO::NULL}` =~ /rubygems/i
-        File.expand_path("..")
-      else
-        File.expand_path("tmp/rubygems")
-      end
-    end
-
-    task "co" => "setup_co"
-    task "rubygems:all" => "co"
-  end
-
   desc "Run the tests on Travis CI against a RubyGem version (using ENV['RGV'])"
   task :travis do
     rg = ENV["RGV"] || raise("RubyGems version is required on Travis!")
 
-    rg = "co" if File.directory?(File.expand_path(ENV["RGV"]))
-
     # disallow making network requests on CI
     ENV["BUNDLER_SPEC_PRE_RECORDED"] = "TRUE"
 
     puts "\n\e[1;33m[Travis CI] Running bundler specs against RubyGems #{rg}\e[m\n\n"
-    specs = safe_task { Rake::Task["spec:rubygems:#{rg}"].invoke }
+    specs = safe_task { Rake::Task["spec"].invoke }
 
-    Rake::Task["spec:rubygems:#{rg}"].reenable
+    Rake::Task["spec"].reenable
 
     puts "\n\e[1;33m[Travis CI] Running bundler sudo specs against RubyGems #{rg}\e[m\n\n"
-    sudos = system("sudo -E rake spec:rubygems:#{rg}:sudo")
+    sudos = system("sudo -E rake spec:sudo")
     # clean up by chowning the newly root-owned tmp directory back to the travis user
     system("sudo chown -R #{ENV["USER"]} #{File.join(File.dirname(__FILE__), "tmp")}")
 
-    Rake::Task["spec:rubygems:#{rg}"].reenable
+    Rake::Task["spec"].reenable
 
     puts "\n\e[1;33m[Travis CI] Running bundler real world specs against RubyGems #{rg}\e[m\n\n"
-    realworld = safe_task { Rake::Task["spec:rubygems:#{rg}:realworld"].invoke }
+    realworld = safe_task { Rake::Task["spec:realworld"].invoke }
 
     { "specs" => specs, "sudo" => sudos, "realworld" => realworld }.each do |name, passed|
       if passed
diff --git a/bin/parallel_rspec b/bin/parallel_rspec
index 9783533198..c6fb33d583 100755
--- a/bin/parallel_rspec
+++ b/bin/parallel_rspec
@@ -1,8 +1,6 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-load File.expand_path("../with_rubygems", __FILE__) if ENV["RGV"]
-
 require_relative "../spec/support/rubygems_ext"
 
 Spec::Rubygems.gem_load("parallel_tests", "parallel_rspec")
diff --git a/bin/rake b/bin/rake
index 2fb69d19f3..6a443ab2d9 100755
--- a/bin/rake
+++ b/bin/rake
@@ -1,8 +1,6 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-load File.expand_path("../with_rubygems", __FILE__) if ENV["RGV"]
-
 require_relative "../spec/support/rubygems_ext"
 
 Spec::Rubygems.gem_load("rake", "rake")
diff --git a/bin/ronn b/bin/ronn
index e47fb518a4..d7084e307e 100755
--- a/bin/ronn
+++ b/bin/ronn
@@ -1,8 +1,6 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-load File.expand_path("../with_rubygems", __FILE__) if ENV["RGV"]
-
 require_relative "../spec/support/rubygems_ext"
 
 Spec::Rubygems.gem_load("ronn", "ronn")
diff --git a/bin/rspec b/bin/rspec
index 4c139156f9..250b9cfb54 100755
--- a/bin/rspec
+++ b/bin/rspec
@@ -1,8 +1,6 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-load File.expand_path("../with_rubygems", __FILE__) if ENV["RGV"]
-
 require_relative "../spec/support/rubygems_ext"
 
 Spec::Rubygems.gem_load("rspec-core", "rspec")
diff --git a/bin/rubocop b/bin/rubocop
index 818aaf7a9d..3716bffe31 100755
--- a/bin/rubocop
+++ b/bin/rubocop
@@ -1,8 +1,6 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
-load File.expand_path("../with_rubygems", __FILE__) if ENV["RGV"]
-
 require_relative "../spec/support/rubygems_ext"
 
 Spec::Rubygems.gem_load("rubocop", "rubocop")
diff --git a/bin/with_rubygems b/bin/with_rubygems
deleted file mode 100755
index 59365e40ce..0000000000
--- a/bin/with_rubygems
+++ /dev/null
@@ -1,45 +0,0 @@
-#!/usr/bin/env ruby
-# frozen_string_literal: true
-
-require "pathname"
-require_relative "../spec/support/helpers"
-
-class RubygemsVersionManager
-  include Spec::Helpers
-end
-
-rubygems_version_manager = RubygemsVersionManager.new
-
-version = ENV.delete("RGV")
-rubygems_path = Pathname.new(version).expand_path
-unless rubygems_path.directory?
-  rubygems_path = Pathname.new("tmp/rubygems").expand_path
-  unless rubygems_path.directory?
-    rubygems_path.parent.mkpath
-    rubygems_version_manager.sys_exec!("git clone https://github.com/rubygems/rubygems.git #{rubygems_path}")
-  end
-  Dir.chdir(rubygems_path) do
-    rubygems_version_manager.sys_exec!("git remote update")
-    version = "v#{version}" if version =~ /\A\d/
-    rubygems_version_manager.sys_exec!("git checkout #{version} --quiet")
-  end
-end
-
-rubygems_lib = rubygems_path + "lib"
-ENV["RUBYOPT"] = %(-I#{rubygems_lib} #{ENV["RUBYOPT"]})
-
-if $0 != __FILE__
-  ARGV.unshift($0)
-elsif cmd = ARGV.first
-  possible_dirs = [
-    Pathname.new(__FILE__) + "..",
-    Pathname.new(__FILE__) + "../../exe",
-    rubygems_path + "bin",
-  ]
-  cmd = possible_dirs.map do |dir|
-    dir.join(cmd).expand_path
-  end.find(&:file?)
-  ARGV[0] = cmd.to_s if cmd
-end
-
-exec(*ARGV)
diff --git a/spec/install/gemfile/git_spec.rb b/spec/install/gemfile/git_spec.rb
index 7eb05a995c..014724a292 100644
--- a/spec/install/gemfile/git_spec.rb
+++ b/spec/install/gemfile/git_spec.rb
@@ -1056,7 +1056,7 @@ RSpec.describe "bundle install with git sources" do
 
       File.open(lib_path("install_hooks.rb"), "w") do |h|
         h.write <<-H
-          require 'rubygems'
+          require '#{spec_dir}/support/rubygems'
           Gem.pre_install_hooks << lambda do |inst|
             STDERR.puts "Ran pre-install hook: \#{inst.spec.full_name}"
           end
@@ -1076,7 +1076,7 @@ RSpec.describe "bundle install with git sources" do
 
       File.open(lib_path("install_hooks.rb"), "w") do |h|
         h.write <<-H
-          require 'rubygems'
+          require '#{spec_dir}/support/rubygems'
           Gem.post_install_hooks << lambda do |inst|
             STDERR.puts "Ran post-install hook: \#{inst.spec.full_name}"
           end
@@ -1096,7 +1096,7 @@ RSpec.describe "bundle install with git sources" do
 
       File.open(lib_path("install_hooks.rb"), "w") do |h|
         h.write <<-H
-          require 'rubygems'
+          require '#{spec_dir}/support/rubygems'
           Gem.pre_install_hooks << lambda do |inst|
             false
           end
diff --git a/spec/install/gemfile/path_spec.rb b/spec/install/gemfile/path_spec.rb
index 3f2e5bdfc3..5261e18bbe 100644
--- a/spec/install/gemfile/path_spec.rb
+++ b/spec/install/gemfile/path_spec.rb
@@ -672,7 +672,7 @@ RSpec.describe "bundle install with explicit source paths" do
 
       File.open(lib_path("install_hooks.rb"), "w") do |h|
         h.write <<-H
-          require 'rubygems'
+          require '#{spec_dir}/support/rubygems'
           Gem.pre_install_hooks << lambda do |inst|
             STDERR.puts "Ran pre-install hook: \#{inst.spec.full_name}"
           end
@@ -692,7 +692,7 @@ RSpec.describe "bundle install with explicit source paths" do
 
       File.open(lib_path("install_hooks.rb"), "w") do |h|
         h.write <<-H
-          require 'rubygems'
+          require '#{spec_dir}/support/rubygems'
           Gem.post_install_hooks << lambda do |inst|
             STDERR.puts "Ran post-install hook: \#{inst.spec.full_name}"
           end
@@ -712,7 +712,7 @@ RSpec.describe "bundle install with explicit source paths" do
 
       File.open(lib_path("install_hooks.rb"), "w") do |h|
         h.write <<-H
-          require 'rubygems'
+          require '#{spec_dir}/support/rubygems'
           Gem.pre_install_hooks << lambda do |inst|
             false
           end
diff --git a/spec/support/helpers.rb b/spec/support/helpers.rb
index 92444ddd2f..ffcde39df7 100644
--- a/spec/support/helpers.rb
+++ b/spec/support/helpers.rb
@@ -116,6 +116,7 @@ module Spec
       env["PATH"].gsub!("#{Path.root}/exe", "") if env["PATH"] && system_bundler
 
       requires = options.delete(:requires) || []
+      requires << "support/rubygems"
       requires << "support/hax"
 
       artifice = options.delete(:artifice) do
@@ -149,7 +150,7 @@ module Spec
         end
       end.join
 
-      cmd = "#{sudo} #{Gem.ruby} #{load_path_str} #{requires_str} #{bundle_bin} #{cmd}#{args}"
+      cmd = "#{sudo} #{Gem.ruby} --disable-gems #{load_path_str} #{requires_str} #{bundle_bin} #{cmd}#{args}"
       sys_exec(cmd, env) {|i, o, thr| yield i, o, thr if block_given? }
     end
     bang :bundle
diff --git a/spec/support/path.rb b/spec/support/path.rb
index db28454792..79b55dd42a 100644
--- a/spec/support/path.rb
+++ b/spec/support/path.rb
@@ -22,7 +22,7 @@ module Spec
     end
 
     def gem_bin
-      @gem_bin ||= ruby_core? ? ENV["GEM_COMMAND"] : "#{Gem.ruby} -S gem --backtrace"
+      @gem_bin ||= ruby_core? ? ENV["GEM_COMMAND"] : "#{Gem.ruby} --disable-gems -r#{spec_dir}/support/rubygems -S gem --backtrace"
     end
 
     def spec_dir
diff --git a/spec/support/rubygems.rb b/spec/support/rubygems.rb
new file mode 100644
index 0000000000..e60f9a928e
--- /dev/null
+++ b/spec/support/rubygems.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+require_relative "rubygems_version_manager"
+
+RubygemsVersionManager.new(ENV["RGV"]).switch
+
+require "rubygems"
diff --git a/spec/support/rubygems_ext.rb b/spec/support/rubygems_ext.rb
index 22374d9f39..aee1f85594 100644
--- a/spec/support/rubygems_ext.rb
+++ b/spec/support/rubygems_ext.rb
@@ -40,6 +40,7 @@ module Spec
     end
 
     def gem_load(gem_name, bin_container)
+      require_relative "rubygems"
       gem_load_and_activate(gem_name, bin_container)
     end
 
diff --git a/spec/support/rubygems_version_manager.rb b/spec/support/rubygems_version_manager.rb
new file mode 100644
index 0000000000..83d33da7c3
--- /dev/null
+++ b/spec/support/rubygems_version_manager.rb
@@ -0,0 +1,110 @@
+# frozen_string_literal: true
+
+require "pathname"
+require_relative "helpers"
+
+class RubygemsVersionManager
+  include Spec::Helpers
+
+  def initialize(env_version)
+    @env_version = env_version
+  end
+
+  def switch
+    return if use_system?
+
+    unrequire_rubygems_if_needed
+
+    switch_local_copy
+
+    prepare_environment
+  end
+
+private
+
+  def use_system?
+    @env_version.nil?
+  end
+
+  def unrequire_rubygems_if_needed
+    return unless rubygems_unrequire_needed?
+
+    require "rbconfig"
+
+    ruby = File.join(RbConfig::CONFIG["bindir"], RbConfig::CONFIG["ruby_install_name"])
+    ruby << RbConfig::CONFIG["EXEEXT"]
+
+    cmd = [ruby, $0, *ARGV].compact
+    cmd[1, 0] = "--disable-gems"
+
+    exec(ENV, *cmd)
+  end
+
+  def switch_local_copy
+    Dir.chdir(local_copy_path) do
+      sys_exec!("git remote update")
+      sys_exec!("git checkout #{target_tag_version} --quiet")
+    end
+  end
+
+  def prepare_environment
+    $:.unshift File.expand_path("lib", local_copy_path)
+  end
+
+  def rubygems_unrequire_needed?
+    defined?(Gem) && Gem::VERSION != target_gem_version
+  end
+
+  def target_gem_version
+    @target_gem_version ||= resolve_target_gem_version
+  end
+
+  def target_tag_version
+    @target_tag_version ||= resolve_target_tag_version
+  end
+
+  def local_copy_path
+    @local_copy_path ||= resolve_local_copy_path
+  end
+
+  def resolve_local_copy_path
+    return expanded_env_version if env_version_is_path?
+
+    rubygems_path = Pathname.new("../../tmp/rubygems").expand_path(__dir__)
+
+    unless rubygems_path.directory?
+      rubygems_path.parent.mkpath
+      sys_exec!("git clone https://github.com/rubygems/rubygems.git #{rubygems_path}")
+    end
+
+    rubygems_path
+  end
+
+  def env_version_is_path?
+    expanded_env_version.directory?
+  end
+
+  def expanded_env_version
+    @expanded_env_version ||= Pathname.new(@env_version).expand_path
+  end
+
+  def resolve_target_tag_version
+    return "v#{@env_version}" if @env_version.match(/^\d/)
+
+    return "master" if @env_version == master_gem_version
+
+    @env_version
+  end
+
+  def resolve_target_gem_version
+    return @env_version[1..-1] if @env_version.match(/^v/)
+
+    return master_gem_version if @env_version == "master"
+
+    @env_version
+  end
+
+  def master_gem_version
+    "3.1.0.pre1"
+  end
+end