Added that gems can now be plugins if they include rails/init.rb (closes #11444) [jbarnette]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@9101 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

3 files changed, 64 insertions, 2 deletions

diff --git a/railties/lib/initializer.rb b/railties/lib/initializer.rb
index 32e6c5251b..c3ebffdf03 100644
--- a/railties/lib/initializer.rb
+++ b/railties/lib/initializer.rb
@@ -72,6 +72,7 @@ module Rails
       Rails.configuration = configuration
 
       check_ruby_version
+      install_gem_spec_stubs
       set_load_path
       
       require_frameworks
@@ -118,6 +119,26 @@ module Rails
       require 'ruby_version_check'
     end
 
+    # If Rails is vendored and RubyGems is available, install stub GemSpecs
+    # for Rails, ActiveSupport, ActiveRecord, ActionPack, ActionMailer, and
+    # ActiveResource. This allows Gem plugins to depend on Rails even when
+    # the Gem version of Rails shouldn't be loaded.
+    def install_gem_spec_stubs
+      if Rails.vendor_rails?
+        begin; require "rubygems"; rescue LoadError; return; end
+
+        stubs = %w(rails activesupport activerecord actionpack actionmailer activeresource)
+        stubs.reject! { |s| Gem.loaded_specs.key?(s) }
+
+        stubs.each do |stub|
+          Gem.loaded_specs[stub] = Gem::Specification.new do |s|
+            s.name = stub
+            s.version = Rails::VERSION::STRING
+          end
+        end
+      end
+    end
+
     # Set the <tt>$LOAD_PATH</tt> based on the value of
     # Configuration#load_paths. Duplicates are removed.
     def set_load_path
@@ -666,7 +687,9 @@ module Rails
       end
 
       def default_plugin_locators
-        [Plugin::FileSystemLocator]
+        locators = []
+        locators << Plugin::GemLocator if defined? Gem
+        locators << Plugin::FileSystemLocator
       end
 
       def default_plugin_loader
diff --git a/railties/lib/rails/plugin.rb b/railties/lib/rails/plugin.rb
index 03fa309ca3..b45ec7de0e 100644
--- a/railties/lib/rails/plugin.rb
+++ b/railties/lib/rails/plugin.rb
@@ -97,4 +97,24 @@ module Rails
          end
       end               
   end
+
+  # This Plugin subclass represents a Gem plugin. It behaves exactly like a
+  # "traditional" Rails plugin, but doesn't expose any additional load paths,
+  # since RubyGems has already taken care of things.
+  class GemPlugin < Plugin
+
+    # Initialize this plugin from a Gem::Specification.
+    def initialize(spec)
+      super(File.join(spec.full_gem_path, "rails"))
+      @name = spec.name
+    end
+
+    def valid?
+      true
+    end
+
+    def load_paths
+      []
+    end
+  end
 end
\ No newline at end of file
diff --git a/railties/lib/rails/plugin/locator.rb b/railties/lib/rails/plugin/locator.rb
index b27e904b12..0b7923cfb6 100644
--- a/railties/lib/rails/plugin/locator.rb
+++ b/railties/lib/rails/plugin/locator.rb
@@ -72,7 +72,26 @@ module Rails
             plugins
           end
         end
-        
+    end
+
+    # The GemLocator scans all the loaded RubyGems, looking for gems with
+    # a <tt>rails/init.rb</tt> file.
+    class GemLocator < Locator
+      def plugins
+        specs = Gem.loaded_specs.values.select do |spec|
+          spec.loaded_from && # prune stubs
+            File.exist?(File.join(spec.full_gem_path, "rails", "init.rb"))
+        end
+
+        require "rubygems/dependency_list"
+
+        deps = Gem::DependencyList.new
+        deps.add(*specs)
+
+        deps.dependency_order.collect do |spec|
+          Rails::GemPlugin.new(spec)
+        end
+      end
     end
   end
 end
\ No newline at end of file