1 files changed, 17 insertions, 4 deletions
diff --git a/railties/lib/rails/gem_dependency.rb b/railties/lib/rails/gem_dependency.rb
index 3062a77104..ee3d0d81ba 100644
--- a/railties/lib/rails/gem_dependency.rb
+++ b/railties/lib/rails/gem_dependency.rb
@@ -29,6 +29,15 @@ module Rails
       end
     end
 
+    def self.from_directory_name(directory_name)
+      directory_name_parts = File.basename(directory_name).split('-')
+      name    = directory_name_parts[0..-2].join('-')
+      version = directory_name_parts.last
+      self.new(name, :version => version)
+    rescue ArgumentError => e
+      raise "Unable to determine gem name and version from '#{directory_name}'"
+    end
+
     def initialize(name, options = {})
       require 'rubygems' unless Object.const_defined?(:Gem)
 
@@ -101,8 +110,12 @@ module Rails
     end
 
     def built?
-      # TODO: If Rubygems ever gives us a way to detect this, we should use it
-      false
+      return false unless frozen?
+      specification.extensions.each do |ext|
+        makefile = File.join(unpacked_gem_directory, File.dirname(ext), 'Makefile')
+        return false unless File.exists?(makefile)
+      end
+      true
     end
 
     def framework_gem?
@@ -155,9 +168,9 @@ module Rails
       specification && File.exists?(unpacked_gem_directory)
     end
 
-    def build
+    def build(options={})
       require 'rails/gem_builder'
-      unless built?
+      if options[:force] || !built?
         return unless File.exists?(unpacked_specification_filename)
         spec = YAML::load_file(unpacked_specification_filename)
         Rails::GemBuilder.new(spec, unpacked_gem_directory).build_extensions