Added class collision checks.

4 files changed, 49 insertions, 8 deletions

diff --git a/railties/lib/generators/base.rb b/railties/lib/generators/base.rb
index e7d0ac80eb..d4bce83161 100644
--- a/railties/lib/generators/base.rb
+++ b/railties/lib/generators/base.rb
@@ -29,6 +29,39 @@ module Rails
 
       protected
 
+        # Check whether the given class names are already taken by Ruby or Rails.
+        # In the future, expand to check other namespaces such as the rest of
+        # the user's app.
+        #
+        def class_collisions(*class_names)
+          return unless behavior == :invoke
+
+          class_names.flatten.each do |class_name|
+            class_name = class_name.to_s
+            next if class_name.strip.empty?
+
+            # Split the class from its module nesting
+            nesting = class_name.split('::')
+            last_name = nesting.pop
+
+            # Hack to limit const_defined? to non-inherited on 1.9
+            extra = []
+            extra << false unless Object.method(:const_defined?).arity == 1
+
+            # Extract the last Module in the nesting
+            last = nesting.inject(Object) do |last, nest|
+              break unless last.const_defined?(nest, *extra)
+              last.const_get(nest)
+            end
+
+            if last && last.const_defined?(last_name.camelize, *extra)
+              raise Error, "The name '#{class_name}' is either already used in your application " <<
+                           "or reserved by Ruby on Rails. Please choose an alternative and run "  <<
+                           "this generator again."
+            end
+          end
+        end
+
         # Use Rails default banner.
         #
         def self.banner
diff --git a/railties/lib/generators/rails/metal/metal_generator.rb b/railties/lib/generators/rails/metal/metal_generator.rb
index ba062b30be..f8833ecec3 100644
--- a/railties/lib/generators/rails/metal/metal_generator.rb
+++ b/railties/lib/generators/rails/metal/metal_generator.rb
@@ -1,7 +1,13 @@
-module Rails::Generators
-  class MetalGenerator < NamedBase
-    def create_file
-      template "metal.rb", "app/metal/#{file_name}.rb"
+module Rails
+  module Generators
+    class MetalGenerator < NamedBase
+      def check_class_collision
+        class_collisions class_name
+      end
+
+      def create_file
+        template "metal.rb", "app/metal/#{file_name}.rb"
+      end
     end
   end
 end
diff --git a/railties/lib/generators/rails/observer/observer_generator.rb b/railties/lib/generators/rails/observer/observer_generator.rb
index 9a5253a0ad..e5e1be39dc 100644
--- a/railties/lib/generators/rails/observer/observer_generator.rb
+++ b/railties/lib/generators/rails/observer/observer_generator.rb
@@ -1,8 +1,9 @@
 module Rails
   module Generators
     class ObserverGenerator < NamedBase
-      # TODO Check class collisions
-      # class_collisions "#{class_name}Observer", "#{class_name}ObserverTest"
+      def check_class_collision
+        class_collisions "#{class_name}Observer"
+      end
 
       def create_observer_file
         template 'observer.rb', File.join('app/models', class_path, "#{file_name}_observer.rb")
diff --git a/railties/lib/generators/rails/plugin/plugin_generator.rb b/railties/lib/generators/rails/plugin/plugin_generator.rb
index eb36cea0f1..4dbb3bfc0d 100644
--- a/railties/lib/generators/rails/plugin/plugin_generator.rb
+++ b/railties/lib/generators/rails/plugin/plugin_generator.rb
@@ -7,8 +7,9 @@ module Rails
       class_option :with_generator, :type => :boolean, :aliases => "-g", :default => false,
                                     :desc => "When supplied creates generator base files."
 
-      # TODO Check class collision
-      # class_collision class_name
+      def check_class_collision
+        class_collisions class_name
+      end
 
       def create_root
         self.root = File.expand_path("vendor/plugins/#{file_name}", root)