url_for does not modify polymorphic options

The `url_for` methods in `actionpack` and `actionview`
now make a copy of the provided options
before generating polymorphic paths or URLs.

The bug in the previous behavior
is most noticeable in a case like:

    url_options = [:new, :post, param: 'value']

    if current_page?(url_options)
      css_class = "active"
    end

    link_to "New Post", url_options, class: css_class

actionpack/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   `url_for` does not modify its arguments when generating polymorphic URLs.
+
+    *Bernerd Schaefer*
+
 *   Update `ActionController::TestSession#fetch` to behave more like
     `ActionDispatch::Request::Session#fetch` when using non-string keys.
 

actionpack/lib/action_dispatch/routing/url_for.rb

@@ -180,7 +180,8 @@ module ActionDispatch
         when Symbol
           HelperMethodBuilder.url.handle_string_call self, options
         when Array
-          polymorphic_url(options, options.extract_options!)
+          components = options.dup
+          polymorphic_url(components, components.extract_options!)
         when Class
           HelperMethodBuilder.url.handle_class_call self, options
         else

actionpack/test/controller/url_for_test.rb

@@ -451,6 +451,26 @@ module AbstractController
         end
       end
 
+      def test_url_for_with_array_is_unmodified
+        with_routing do |set|
+          set.draw do
+            namespace :admin do
+              resources :posts
+            end
+          end
+
+          kls = Class.new { include set.url_helpers }
+          kls.default_url_options[:host] = 'www.basecamphq.com'
+
+          original_components = [:new, :admin, :post, { param: 'value' }]
+          components = original_components.dup
+
+          kls.new.url_for(components)
+
+          assert_equal(original_components, components)
+        end
+      end
+
       private
         def extract_params(url)
           url.split('?', 2).last.split('&').sort

actionview/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   `url_for` does not modify its arguments when generating polymorphic URLs.
+
+    *Bernerd Schaefer*
+
 *   `number_to_currency` and `number_with_delimiter` now accept custom `delimiter_pattern` option 
      to handle placement of delimiter, to support currency formats like INR 
      

actionview/lib/action_view/routing_url_for.rb

@@ -105,10 +105,11 @@ module ActionView
       when :back
         _back_url
       when Array
+        components = options.dup
         if _generate_paths_by_default
-          polymorphic_path(options, options.extract_options!)
+          polymorphic_path(components, components.extract_options!)
         else
-          polymorphic_url(options, options.extract_options!)
+          polymorphic_url(components, components.extract_options!)
         end
       else
         method = _generate_paths_by_default ? :path : :url

actionview/test/template/url_helper_test.rb

@@ -785,6 +785,13 @@ class SessionsController < ActionController::Base
     @session = Session.new(params[:id])
     render inline: "<%= url_for([@workshop, @session]) %>\n<%= link_to('Session', [@workshop, @session]) %>"
   end
+
+  def edit
+    @workshop = Workshop.new(params[:workshop_id])
+    @session = Session.new(params[:id])
+    @url = [@workshop, @session, format: params[:format]]
+    render inline: "<%= url_for(@url) %>\n<%= link_to('Session', @url) %>"
+  end
 end
 
 class PolymorphicControllerTest < ActionController::TestCase
@@ -815,4 +822,11 @@ class PolymorphicControllerTest < ActionController::TestCase
     get :show, params: { workshop_id: 1, id: 1 }
     assert_equal %{/workshops/1/sessions/1\n<a href="/workshops/1/sessions/1">Session</a>}, @response.body
   end
+
+  def test_existing_nested_resource_with_params
+    @controller = SessionsController.new
+
+    get :edit, params: { workshop_id: 1, id: 1, format: "json"  }
+    assert_equal %{/workshops/1/sessions/1.json\n<a href="/workshops/1/sessions/1.json">Session</a>}, @response.body
+  end
 end