[rubygems/rubygems] Don't write outside of destdir when regenerating plugins

https://github.com/rubygems/rubygems/commit/141ef4cb9a

lib/rubygems/commands/pristine_command.rb

@@ -50,6 +50,11 @@ class Gem::Commands::PristineCommand < Gem::Command
       options[:env_shebang] = value
     end
 
+    add_option('-i', '--install-dir DIR',
+               'Gem repository to get binstubs and plugins installed') do |value, options|
+      options[:install_dir] = File.expand_path(value)
+    end
+
     add_option('-n', '--bindir DIR',
                'Directory where executables are',
                'located') do |value, options|
@@ -163,11 +168,12 @@ extensions will be restored.
         end
 
       bin_dir = options[:bin_dir] if options[:bin_dir]
+      install_dir = options[:install_dir] if options[:install_dir]
 
       installer_options = {
         :wrappers => true,
         :force => true,
-        :install_dir => spec.base_dir,
+        :install_dir => install_dir || spec.base_dir,
         :env_shebang => env_shebang,
         :build_args => spec.build_args,
         :bin_dir => bin_dir,
@@ -177,7 +183,7 @@ extensions will be restored.
         installer = Gem::Installer.for_spec(spec, installer_options)
         installer.generate_bin
       elsif options[:only_plugins]
-        installer = Gem::Installer.for_spec(spec)
+        installer = Gem::Installer.for_spec(spec, installer_options)
         installer.generate_plugins
       else
         installer = Gem::Installer.at(gem, installer_options)

lib/rubygems/commands/setup_command.rb

@@ -610,6 +610,7 @@ abort "#{deprecation_message}"
 
     args = %w[--all --only-plugins --silent]
     args << "--bindir=#{bindir}"
+    args << "--install-dir=#{default_dir}"
 
     command = Gem::Commands::PristineCommand.new
     command.invoke(*args)

test/rubygems/test_gem_commands_setup_command.rb

@@ -156,6 +156,21 @@ class TestGemCommandsSetupCommand < Gem::TestCase
     assert_match %r{\A#!\s*#{bin_env}#{ruby_exec}}, File.read(gem_bin_path)
   end
 
+  def test_destdir_flag_does_not_try_to_write_to_the_default_gem_home
+    FileUtils.chmod "-w", File.join(@gemhome, "plugins")
+
+    destdir = File.join(@tempdir, 'foo')
+
+    @cmd.options[:destdir] = destdir
+    @cmd.execute
+
+    spec = Gem::Specification.load("bundler/bundler.gemspec")
+
+    spec.executables.each do |e|
+      assert_path_exist File.join destdir, @gemhome.gsub(/^[a-zA-Z]:/, ''), 'gems', spec.full_name, spec.bindir, e
+    end
+  end
+
   def test_files_in
     assert_equal %w[rubygems.rb rubygems/requirement.rb rubygems/ssl_certs/rubygems.org/foo.pem],
                  @cmd.files_in('lib').sort