Prevent conflict between mime types and Object methods

Assuming the type ":touch", Collector.new was calling
send(:touch), which instead of triggering method_missing
and generating a new collector method, actually
invoked the private method `touch` inherited from
Object.

By generating the method for each mime type as it
is registered, the private methods on Object can
never be reached by `send`, because the `Collector`
will have them before `send` is called on it.

To do this, a callback mechanism was added to Mime::Type

This allows someone to add a callback for whenever
a new mime type is registered. The callback then
gets called with the new mime as a parameter.

This is then used in AbstractController::Collector
to generate new collector methods after each mime
is registered.

actionpack/lib/abstract_controller/collector.rb

@@ -16,6 +16,10 @@ def #{sym}(*args, &block)                # def html(*args, &block)
       generate_method_for_mime(mime)
     end
 
+    Mime::Type.register_callback do |mime|
+      generate_method_for_mime(mime) unless self.instance_methods.include?(mime.to_sym)
+    end
+
   protected
 
     def method_missing(symbol, &block)

actionpack/lib/action_dispatch/http/mime_type.rb

@@ -58,6 +58,8 @@ class Type
     cattr_reader :browser_generated_types
     attr_reader :symbol
 
+    @register_callbacks = []
+
     # A simple helper class used in parsing the accept header
     class AcceptItem #:nodoc:
       attr_accessor :order, :name, :q
@@ -89,6 +91,10 @@ class << self
       TRAILING_STAR_REGEXP = /(text|application)\/\*/
       PARAMETER_SEPARATOR_REGEXP = /;\s*\w+="?\w+"?/
 
+      def register_callback(&block)
+        @register_callbacks << block
+      end
+
       def lookup(string)
         LOOKUP[string]
       end
@@ -106,10 +112,15 @@ def register_alias(string, symbol, extension_synonyms = [])
       def register(string, symbol, mime_type_synonyms = [], extension_synonyms = [], skip_lookup = false)
         Mime.const_set(symbol.upcase, Type.new(string, symbol, mime_type_synonyms))
 
-        SET << Mime.const_get(symbol.upcase)
+        new_mime = Mime.const_get(symbol.upcase)
+        SET << new_mime
 
         ([string] + mime_type_synonyms).each { |str| LOOKUP[str] = SET.last } unless skip_lookup
         ([symbol] + extension_synonyms).each { |ext| EXTENSION_LOOKUP[ext.to_s] = SET.last }
+
+        @register_callbacks.each do |callback|
+          callback.call(new_mime)
+        end
       end
 
       def parse(accept_header)

actionpack/test/controller/mime_responds_test.rb

@@ -505,7 +505,7 @@ def test_invalid_format
 end
 
 class RespondWithController < ActionController::Base
-  respond_to :html, :json
+  respond_to :html, :json, :touch
   respond_to :xml, :except => :using_resource_with_block
   respond_to :js,  :only => [ :using_resource_with_block, :using_resource, 'using_hash_resource' ]
 
@@ -623,12 +623,14 @@ def setup
     super
     @request.host = "www.example.com"
     Mime::Type.register_alias('text/html', :iphone)
+    Mime::Type.register_alias('text/html', :touch)
     Mime::Type.register('text/x-mobile', :mobile)
   end
 
   def teardown
     super
     Mime::Type.unregister(:iphone)
+    Mime::Type.unregister(:touch)
     Mime::Type.unregister(:mobile)
   end
 

actionpack/test/dispatch/mime_type_test.rb

@@ -118,6 +118,20 @@ class MimeTypeTest < ActiveSupport::TestCase
     end
   end
 
+  test "register callbacks" do
+    begin
+      registered_mimes = []
+      Mime::Type.register_callback do |mime|
+        registered_mimes << mime
+      end
+
+      Mime::Type.register("text/foo", :foo)
+      assert_equal registered_mimes, [Mime::FOO]
+    ensure
+      Mime::Type.unregister(:FOO)
+    end
+  end
+
   test "custom type with extension aliases" do
     begin
       Mime::Type.register "text/foobar", :foobar, [], [:foo, "bar"]