Support XDG_* (#2174)

* Support XDG_CONFIG_HOME for gemrc.

* Support XDG_DATA_HOME for .gem

* Added test for XDG_DATA_HOME

* Do not reuse environmental variable.

* Unify .rdoc path to RDoc.home.

* Support XDG_DATA_HOME for .rdoc

* Ignore exists?

* Extracted config_home path

* Use XDG_CONFIG_HOME for default credential path

* Fixed inconsistency location.

* Fixed the broken tests.

* Support XDG_CONFIG_HOME for irbrc

* Introduce Gem.cache_home as XDG_CACHE_HOME

* Use Gem.cache_home instead of Gem.config_home for the credential file of RubyGems.

* Initialized the old configurations

* Fixed test failure related the configuration initialization

* restore XDG_DATA_HOME

* Fixed the broken examples of bundler with XDG_*

* Do not modify environmental variable on test file

* Use XDG_DATA_HOME insted of XDG_CACHE_HOME for credential file

* stub out Gem.data_home

* Move dir accessor to defaults.rb file

* Use XDG_DATA_HOME for signed gem features

* Use XDG_DATA_HOME for spec cache

* Do not rely on Gem.user_home

* Gem.user_home is always exists. Don't need to use FileUitls.mkdir_p

* Bump support version to RubyGems 3.2.0+

* Removed the needless fallback configuration

* Fixed the inconsistency methods that are find_config_file and config_file

* Use Gem.configuration.credentials_path instead of hard-coded path

* gem_path is always provided

* Removed the duplicated code of find_home

* Also removed the duplicated code of user_home

* use Gem::UNTAINT instead of untaint for surpressing the warnings

* Use File.directory

* Restore XDG_DATA_HOME

* Use File.write

4 files changed, 116 insertions, 6 deletions

diff --git a/lib/rubygems/config_file.rb b/lib/rubygems/config_file.rb
index 54d8a9c152..393f947d77 100644
--- a/lib/rubygems/config_file.rb
+++ b/lib/rubygems/config_file.rb
@@ -261,7 +261,12 @@ if you believe they were disclosed to a third party.
   # Location of RubyGems.org credentials
 
   def credentials_path
-    File.join Gem.user_home, '.gem', 'credentials'
+    credentials = File.join Gem.user_home, '.gem', 'credentials'
+    if File.exist? credentials
+      credentials
+    else
+      File.join Gem.data_home, "gem", "credentials"
+    end
   end
 
   def load_api_keys
@@ -444,6 +449,10 @@ if you believe they were disclosed to a third party.
 
   # Writes out this config file, replacing its source.
   def write
+    unless File.exist?(File.dirname(config_file_name))
+      FileUtils.mkdir_p File.dirname(config_file_name)
+    end
+
     File.open config_file_name, 'w' do |io|
       io.write to_yaml
     end
diff --git a/lib/rubygems/defaults.rb b/lib/rubygems/defaults.rb
index 0e83f1b006..2d0b077fdc 100644
--- a/lib/rubygems/defaults.rb
+++ b/lib/rubygems/defaults.rb
@@ -20,7 +20,13 @@ module Gem
   # specified in the environment
 
   def self.default_spec_cache_dir
-    File.join Gem.user_home, '.gem', 'specs'
+    default_spec_cache_dir = File.join Gem.user_home, '.gem', 'specs'
+
+    unless File.exist?(default_spec_cache_dir)
+      default_spec_cache_dir = File.join Gem.data_home, 'gem', 'specs'
+    end
+
+    default_spec_cache_dir
   end
 
   ##
@@ -71,15 +77,91 @@ module Gem
   end
 
   ##
+  # Finds the user's home directory.
+  #--
+  # Some comments from the ruby-talk list regarding finding the home
+  # directory:
+  #
+  #   I have HOME, USERPROFILE and HOMEDRIVE + HOMEPATH. Ruby seems
+  #   to be depending on HOME in those code samples. I propose that
+  #   it should fallback to USERPROFILE and HOMEDRIVE + HOMEPATH (at
+  #   least on Win32).
+  #++
+  #--
+  #
+  #++
+
+  def self.find_home
+    Dir.home.dup
+  rescue
+    if Gem.win_platform?
+      File.expand_path File.join(ENV['HOMEDRIVE'] || ENV['SystemDrive'], '/')
+    else
+      File.expand_path "/"
+    end
+  end
+
+  private_class_method :find_home
+
+  ##
+  # The home directory for the user.
+
+  def self.user_home
+    @user_home ||= find_home.tap(&Gem::UNTAINT)
+  end
+
+  ##
   # Path for gems in the user's home directory
 
   def self.user_dir
-    parts = [Gem.user_home, '.gem', ruby_engine]
+    gem_dir = File.join(Gem.user_home, ".gem")
+    gem_dir = File.join(Gem.data_home, "gem") unless File.exist?(gem_dir)
+    parts = [gem_dir, ruby_engine]
     parts << RbConfig::CONFIG['ruby_version'] unless RbConfig::CONFIG['ruby_version'].empty?
     File.join parts
   end
 
   ##
+  # The path to standard location of the user's configuration directory.
+
+  def self.config_home
+    @config_home ||= (ENV["XDG_CONFIG_HOME"] || File.join(Gem.user_home, '.config'))
+  end
+
+  ##
+  # Finds the user's config file
+
+  def self.find_config_file
+    gemrc = File.join Gem.user_home, '.gemrc'
+    if File.exist? gemrc
+      gemrc
+    else
+      File.join Gem.config_home, "gem", "gemrc"
+    end
+  end
+
+  ##
+  # The path to standard location of the user's .gemrc file.
+
+  def self.config_file
+    @config_file ||= find_config_file.tap(&Gem::UNTAINT)
+  end
+
+  ##
+  # The path to standard location of the user's cache directory.
+
+  def self.cache_home
+    @cache_home ||= (ENV["XDG_CACHE_HOME"] || File.join(Gem.user_home, '.cache'))
+  end
+
+  ##
+  # The path to standard location of the user's data directory.
+
+  def self.data_home
+    @data_home ||= (ENV["XDG_DATA_HOME"] || File.join(Gem.user_home, '.local', 'share'))
+  end
+
+  ##
   # How String Gem paths should be split.  Overridable for esoteric platforms.
 
   def self.path_separator
@@ -130,14 +212,26 @@ module Gem
   # The default signing key path
 
   def self.default_key_path
-    File.join Gem.user_home, ".gem", "gem-private_key.pem"
+    default_key_path = File.join Gem.user_home, ".gem", "gem-private_key.pem"
+
+    unless File.exist?(default_key_path)
+      default_key_path = File.join Gem.data_home, "gem", "gem-private_key.pem"
+    end
+
+    default_key_path
   end
 
   ##
   # The default signing certificate chain path
 
   def self.default_cert_path
-    File.join Gem.user_home, ".gem", "gem-public_cert.pem"
+    default_cert_path = File.join Gem.user_home, ".gem", "gem-public_cert.pem"
+
+    unless File.exist?(default_cert_path)
+      default_cert_path = File.join Gem.data_home, "gem", "gem-public_cert.pem"
+    end
+
+    default_cert_path
   end
 
   ##
diff --git a/lib/rubygems/gemcutter_utilities.rb b/lib/rubygems/gemcutter_utilities.rb
index 2950d94dc1..bba9280691 100644
--- a/lib/rubygems/gemcutter_utilities.rb
+++ b/lib/rubygems/gemcutter_utilities.rb
@@ -19,7 +19,7 @@ module Gem::GemcutterUtilities
   def add_key_option
     add_option('-k', '--key KEYNAME', Symbol,
                'Use the given API key',
-               'from ~/.gem/credentials') do |value,options|
+               "from #{Gem.configuration.credentials_path}") do |value,options|
       options[:key] = value
     end
   end
diff --git a/lib/rubygems/test_case.rb b/lib/rubygems/test_case.rb
index e56150caf9..d028254465 100644
--- a/lib/rubygems/test_case.rb
+++ b/lib/rubygems/test_case.rb
@@ -363,6 +363,13 @@ class Gem::TestCase < (defined?(Minitest::Test) ? Minitest::Test : MiniTest::Uni
     Dir.chdir @tempdir
 
     ENV['HOME'] = @userhome
+    FileUtils.mkdir_p File.join(@userhome, ".gem")
+    File.write File.join(@userhome, ".gemrc"), "--- {}"
+    temp_cred = File.join(@userhome, '.gem', 'credentials')
+    FileUtils.mkdir_p File.dirname(temp_cred)
+    File.write temp_cred, ':rubygems_api_key: 701229f217cdf23b1344c7b4b54ca97'
+    File.chmod 0600, temp_cred
+
     Gem.instance_variable_set :@user_home, nil
     Gem.instance_variable_set :@gemdeps, nil
     Gem.instance_variable_set :@env_requirements_by_name, nil