Introduce Rails.gem_version

This method return `Gem::Version.new(Rails.version)`, suggesting a more
reliable way to perform version comparison.

Example:

    Rails.version #=> "4.1.2"
    Rails.gem_version #=> #<Gem::Version "4.1.2">

    Rails.version > "4.1.10" #=> false
    Rails.gem_version > Gem::Version.new("4.1.10") #=> true
    Gem::Requirement.new("~> 4.1.2") =~ Rails.gem_version #=> true

This was originally introduced as `.version` by @charliesome in #8501
but got reverted in #10002 since it was not backward compatible.

Also, updating template for `rake update_versions`.

Rakefile

@@ -66,7 +66,7 @@ task :update_versions do
   version_file = File.read("version.rb")
 
   PROJECTS.each do |project|
-    Dir["#{project}/lib/*/version.rb"].each do |file|
+    Dir["#{project}/lib/*/gem_version.rb"].each do |file|
       File.open(file, "w") do |f|
         f.write version_file.gsub(/Rails/, constants[project])
       end

actionmailer/lib/action_mailer/gem_version.rb

@@ -0,0 +1,15 @@
+module ActionMailer
+  # Returns the version of the currently loaded ActionMailer as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 4
+    MINOR = 2
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end

actionmailer/lib/action_mailer/version.rb

@@ -1,11 +1,8 @@
-module ActionMailer
-  # Returns the version of the currently loaded ActionMailer as a Gem::Version
-  def self.version
-    Gem::Version.new "4.2.0.alpha"
-  end
+require_relative 'gem_version'
 
-  module VERSION #:nodoc:
-    MAJOR, MINOR, TINY, PRE = ActionMailer.version.segments
-    STRING = ActionMailer.version.to_s
+module ActionMailer
+  # Returns the version of the currently loaded ActionMailer as a <tt>Gem::Version</tt>
+  def self.version
+    gem_version
   end
 end

actionpack/lib/action_pack/gem_version.rb

@@ -0,0 +1,15 @@
+module ActionPack
+  # Returns the version of the currently loaded ActionPack as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 4
+    MINOR = 2
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end

actionpack/lib/action_pack/version.rb

@@ -1,11 +1,8 @@
-module ActionPack
-  # Returns the version of the currently loaded ActionPack as a Gem::Version
-  def self.version
-    Gem::Version.new "4.2.0.alpha"
-  end
+require_relative 'gem_version'
 
-  module VERSION #:nodoc:
-    MAJOR, MINOR, TINY, PRE = ActionPack.version.segments
-    STRING = ActionPack.version.to_s
+module ActionPack
+  # Returns the version of the currently loaded ActionPack as a <tt>Gem::Version</tt>
+  def self.version
+    gem_version
   end
 end

actionview/lib/action_view/gem_version.rb

@@ -0,0 +1,15 @@
+module ActionView
+  # Returns the version of the currently loaded ActionView as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 4
+    MINOR = 2
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end

actionview/lib/action_view/version.rb

@@ -1,11 +1,8 @@
-module ActionView
-  # Returns the version of the currently loaded ActionView as a Gem::Version
-  def self.version
-    Gem::Version.new "4.2.0.alpha"
-  end
+require_relative 'gem_version'
 
-  module VERSION #:nodoc:
-    MAJOR, MINOR, TINY, PRE = ActionView.version.segments
-    STRING = ActionView.version.to_s
+module ActionView
+  # Returns the version of the currently loaded ActionView as a <tt>Gem::Version</tt>
+  def self.version
+    gem_version
   end
 end

activemodel/lib/active_model/gem_version.rb

@@ -0,0 +1,15 @@
+module ActiveModel
+  # Returns the version of the currently loaded ActiveModel as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 4
+    MINOR = 2
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end

activemodel/lib/active_model/version.rb

@@ -1,11 +1,8 @@
-module ActiveModel
-  # Returns the version of the currently loaded ActiveModel as a Gem::Version
-  def self.version
-    Gem::Version.new "4.2.0.alpha"
-  end
+require_relative 'gem_version'
 
-  module VERSION #:nodoc:
-    MAJOR, MINOR, TINY, PRE = ActiveModel.version.segments
-    STRING = ActiveModel.version.to_s
+module ActiveModel
+  # Returns the version of the currently loaded ActiveModel as a <tt>Gem::Version</tt>
+  def self.version
+    gem_version
   end
 end

activerecord/lib/active_record/gem_version.rb

@@ -0,0 +1,15 @@
+module ActiveRecord
+  # Returns the version of the currently loaded ActiveRecord as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 4
+    MINOR = 2
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end

activerecord/lib/active_record/version.rb

@@ -1,11 +1,8 @@
-module ActiveRecord
-  # Returns the version of the currently loaded ActiveRecord as a Gem::Version
-  def self.version
-    Gem::Version.new "4.2.0.alpha"
-  end
+require_relative 'gem_version'
 
-  module VERSION #:nodoc:
-    MAJOR, MINOR, TINY, PRE = ActiveRecord.version.segments
-    STRING = ActiveRecord.version.to_s
+module ActiveRecord
+  # Returns the version of the currently loaded ActiveRecord as a <tt>Gem::Version</tt>
+  def self.version
+    gem_version
   end
 end

activesupport/lib/active_support/gem_version.rb

@@ -0,0 +1,15 @@
+module ActiveSupport
+  # Returns the version of the currently loaded ActiveSupport as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 4
+    MINOR = 2
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end

activesupport/lib/active_support/version.rb

@@ -1,11 +1,8 @@
-module ActiveSupport
-  # Returns the version of the currently loaded ActiveSupport as a Gem::Version
-  def self.version
-    Gem::Version.new "4.2.0.alpha"
-  end
+require_relative 'gem_version'
 
-  module VERSION #:nodoc:
-    MAJOR, MINOR, TINY, PRE = ActiveSupport.version.segments
-    STRING = ActiveSupport.version.to_s
+module ActiveSupport
+  # Returns the version of the currently loaded ActiveSupport as a <tt>Gem::Version</tt>
+  def self.version
+    gem_version
   end
 end

railties/CHANGELOG.md

@@ -1,3 +1,18 @@
+*   Introduce `Rails.gem_version` as a convenience method to return
+    `Gem::Version.new(Rails.version)`, suggesting a more reliable way to perform
+    version comparison.
+
+    Example:
+
+        Rails.version #=> "4.1.2"
+        Rails.gem_version #=> #<Gem::Version "4.1.2">
+
+        Rails.version > "4.1.10" #=> false
+        Rails.gem_version > Gem::Version.new("4.1.10") #=> true
+        Gem::Requirement.new("~> 4.1.2") =~ Rails.gem_version #=> true
+
+    *Prem Sichanugrist*
+
 *   Avoid namespacing routes inside engines.
 
     Mountable engines are namespaced by default so the generated routes

railties/lib/rails.rb

@@ -80,10 +80,6 @@ def groups(*groups)
       groups
     end
 
-    def version
-      VERSION::STRING
-    end
-
     def public_path
       application && Pathname.new(application.paths["public"].first)
     end

railties/lib/rails/gem_version.rb

@@ -0,0 +1,15 @@
+module Rails
+  # Returns the version of the currently loaded Rails as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
+  module VERSION
+    MAJOR = 4
+    MINOR = 2
+    TINY  = 0
+    PRE   = "alpha"
+
+    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+  end
+end

railties/lib/rails/version.rb

@@ -1,10 +1,8 @@
-module Rails
-  module VERSION
-    MAJOR = 4
-    MINOR = 2
-    TINY  = 0
-    PRE   = "alpha"
+require_relative 'gem_version'
 
-    STRING = [MAJOR, MINOR, TINY, PRE].compact.join(".")
+module Rails
+  # Returns the version of the currently loaded Rails as a string.
+  def self.version
+    VERSION::STRING
   end
 end

railties/test/version_test.rb

@@ -0,0 +1,12 @@
+require 'abstract_unit'
+
+class VersionTest < ActiveSupport::TestCase
+  def test_rails_version_returns_a_string
+    assert Rails.version.is_a? String
+  end
+
+  def test_rails_gem_version_returns_a_correct_gem_version_object
+    assert Rails.gem_version.is_a? Gem::Version
+    assert_equal Rails.version, Rails.gem_version.to_s
+  end
+end

version.rb

@@ -1,4 +1,9 @@
 module Rails
+  # Returns the version of the currently loaded Rails as a <tt>Gem::Version</tt>
+  def self.gem_version
+    Gem::Version.new VERSION::STRING
+  end
+
   module VERSION
     MAJOR = 4
     MINOR = 2