Refactor railsrc file location to be xdg compliant (#39411)

* Refactor railsrc file location to be xdg compliant

The XDG Base Directory Specification (which is currently used by
FOSS projects such as Git, Tmux, Pry, Rspec) provides a default
location for various file formats, including config/rc files.

This comment refactors app_generator.rb to load railsrc from
XDG_CONFIG_HOME if both XDG_CONFIG_HOME is set and rails/railrc
exists within the XDG_CONFIG_HOME location.

To maintain backwards compatibility it defaults back to ~/.railsrc
if either XDG_CONFIG_HOME is not set or there is no rails/railsrc.

* Refactor default_rc_file based on jonathanhefner PR feedback

* Update generators/rails/app/USAGE to explain railsrc XDG compliance

* Refactor default_rc_file based on sinsoku PR feedback

* Add test for ARGVScrubber.default_rc_file method

fileutils is required because tmpdir does not allow you to create a new
temp directory with a set title 'inside' another temporary directory, a
file is created for railsrc because tempfile creates a custom and unique
name preventing the specification of a file called 'railsrc'

Currently this test is failing because the ARGVScrubber class seems to
be loading directly from the gem (which still has the previous code)
rather than from the file itself. (loading the code in a pry session
and using show-method ARGVScrubber.default_rc_file reveals it is coming
from
gems/railties-6.0.3.3/lib/rails/generators/rails/app/app_generator.rb:536
instead of
railties/lib/rails/generators/rails/app/app_generator.rb

* Switch to double quote strings

* Add file deletion for argv_scrubber test

* Refactor test_xdg_config_no_custom_rc with jonathanhefner feedback

* Add Changelog for railsrc xdg-specification compliance

* Apply backtick and whitespace refactoring suggestsions from jonathanhefner

* Apply jonathanhefner suggested Changelog refactoring

[Rafael Mendonça França + Nick Wolf + Jonathan Hefner]

railties/CHANGELOG.md

@@ -1,3 +1,14 @@
+*   Make railsrc file location xdg-specification compliant
+
+    `rails new` will now look for the default `railsrc` file at
+    `$XDG_CONFIG_HOME/rails/railsrc` (or `~/.config/rails/railsrc` if
+    `XDG_CONFIG_HOME` is not set).  If this file does not exist, `rails new`
+    will fall back to `~/.railsrc`.
+
+    The fallback behaviour means this does not cause any breaking changes.
+
+    *Nick Wolf*
+
 *   Deprecate `config.active_support.use_sha1_digests`
 
     `config.active_support.use_sha1_digests` is deprecated. It is replaced with `config.active_support.hash_digest_class` which allows setting the desired Digest instead. The Rails version defaults have been updated to use this new method as well so the behavior there is unchanged.

railties/lib/rails/generators/rails/app/USAGE

@@ -3,7 +3,8 @@ Description:
     directory structure and configuration at the path you specify.
 
     You can specify extra command-line arguments to be used every time
-    'rails new' runs in the .railsrc configuration file in your home directory.
+    'rails new' runs in the .railsrc configuration file in your home directory,
+    or in $XDG_CONFIG_HOME/rails/railsrc if XDG_CONFIG_HOME is set.
 
     Note that the arguments specified in the .railsrc file don't affect the
     defaults values shown above in this help message.

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -606,7 +606,13 @@ module Rails
       end
 
       def self.default_rc_file
-        File.expand_path("~/.railsrc")
+        xdg_config_home = ENV["XDG_CONFIG_HOME"].presence || "~/.config"
+        xdg_railsrc = File.expand_path("rails/railsrc", xdg_config_home)
+        if File.exist?(xdg_railsrc)
+          xdg_railsrc
+        else
+          File.expand_path("~/.railsrc")
+        end
       end
 
       private

railties/test/generators/argv_scrubber_test.rb

@@ -4,6 +4,8 @@ require "active_support/test_case"
 require "active_support/testing/autorun"
 require "rails/generators/rails/app/app_generator"
 require "tempfile"
+require "fileutils"
+require "env_helpers"
 
 module Rails
   module Generators
@@ -12,6 +14,8 @@ module Rails
       # current behavior of the ARGVScrubber, they do not mean that the class
       # *must* act this way, I just want to prevent regressions.
 
+      include EnvHelpers
+
       def test_version
         ["-v", "--version"].each do |str|
           scrubber = ARGVScrubber.new [str]
@@ -56,6 +60,17 @@ module Rails
         assert_equal [], args
       end
 
+      def test_default_rc_file_with_xdg_config_home
+        Dir.mktmpdir do |dir|
+          rc_file = File.join(dir, "rails/railsrc")
+          FileUtils.mkdir_p(File.dirname(rc_file))
+          FileUtils.touch(rc_file)
+          switch_env("XDG_CONFIG_HOME", dir) do
+            assert_equal rc_file, ARGVScrubber.default_rc_file
+          end
+        end
+      end
+
       def test_new_homedir_rc
         file = Tempfile.new "myrcfile"
         file.puts "--hello-world"