Add link_to :back which uses your referrer with a fallback to a javascript link. #7366 [eventualbuddha, tarmo]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7791 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Add link_to :back which uses your referrer with a fallback to a javascript link. #7366 [eventualbuddha, tarmo]
+
 * error_messages_for and friends also work with local variables.  #9699 [Frederick Cheung]
 
 * Fix url_for, redirect_to, etc. with :controller => :symbol instead of 'string'.  #8562, #9525 [Justin Lynn, Tarmo Tänav, shoe]

actionpack/lib/action_view/helpers/url_helper.rb

@@ -86,8 +86,9 @@ module ActionView
       # of +options+. See the valid options in the documentation for
       # url_for. It's also possible to pass a string instead
       # of an options hash to get a link tag that uses the value of the string as the
-      # href for the link. If nil is passed as a name, the link itself will become
+      # href for the link, or use +:back+ to link to the referrer - a JavaScript back
-      # the name.
+      # link will be used in place of a referrer if none exists. If nil is passed as
+      # a name, the link itself will become the name.
       #
       # ==== Options
       # * <tt>:confirm => 'question?'</tt> -- This will add a JavaScript confirm
@@ -134,7 +135,14 @@ module ActionView
       #        var m = document.createElement('input'); m.setAttribute('type', 'hidden'); m.setAttribute('name', '_method'); 
       #        m.setAttribute('value', 'delete'); f.appendChild(m);f.submit(); };return false;">Delete Image</a>
       def link_to(name, options = {}, html_options = nil)
-        url = options.is_a?(String) ? options : self.url_for(options)
+        url = case options
+          when String
+            options
+          when :back
+            @controller.request.env["HTTP_REFERER"] || 'javascript:history.back()'
+          else
+            self.url_for(options)
+          end
 
         if html_options
           html_options = html_options.stringify_keys

actionpack/test/template/url_helper_test.rb

@@ -1,6 +1,6 @@
 require "#{File.dirname(__FILE__)}/../abstract_unit"
 
-RequestMock = Struct.new("Request", :request_uri, :protocol, :host_with_port)
+RequestMock = Struct.new("Request", :request_uri, :protocol, :host_with_port, :env)
 
 class UrlHelperTest < Test::Unit::TestCase
   include ActionView::Helpers::AssetTagHelper
@@ -109,6 +109,16 @@ class UrlHelperTest < Test::Unit::TestCase
     assert_dom_equal "<a href=\"http://www.example.com?q1=v1&amp;q2=v2\">http://www.example.com?q1=v1&amp;q2=v2</a>", link_to(nil, "http://www.example.com?q1=v1&amp;q2=v2")
   end
 
+  def test_link_tag_with_back
+    @controller.request = RequestMock.new("http://www.example.com/weblog/show", nil, nil, {'HTTP_REFERER' => 'http://www.example.com/referer'})
+    assert_dom_equal "<a href=\"http://www.example.com/referer\">go back</a>", link_to('go back', :back)
+  end
+  
+  def test_link_tag_with_back_and_no_referer
+    @controller.request = RequestMock.new("http://www.example.com/weblog/show", nil, nil, {})
+    assert_dom_equal "<a href=\"javascript:history.back()\">go back</a>", link_to('go back', :back)
+  end
+
   def test_link_tag_with_img
     assert_dom_equal "<a href=\"http://www.example.com\"><img src='/favicon.jpg' /></a>", link_to("<img src='/favicon.jpg' />", "http://www.example.com")
   end