Fix image_tag behavior on windows. [#1085 state:resolved]

Signed-off-by: NPratik Naik <pratiknaik@gmail.com>

actionpack/lib/action_view/helpers/asset_tag_helper.rb

@@ -596,7 +596,7 @@ def compute_public_path(source)
             end
 
             def missing_extension?(source)
-              extension && File.extname(source).blank? || File.exist?(File.join(ASSETS_DIR, directory, "#{source}.#{extension}"))
+              extension && (File.extname(source).blank? || File.exist?(File.join(ASSETS_DIR, directory, "#{source}.#{extension}")))
             end
 
             def prepend_relative_url_root(source)

actionpack/test/template/asset_tag_helper_test.rb

@@ -230,6 +230,19 @@ def test_image_tag
     ImageLinkToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
 
+  uses_mocha 'test image tag with windows behaviour' do
+    def test_image_tag_windows_behaviour
+      old_asset_id, ENV["RAILS_ASSET_ID"] = ENV["RAILS_ASSET_ID"], "1"
+      # This simulates the behaviour of File#exist? on windows when testing a file ending in "."
+      # If the file "rails.png" exists, windows will return true when asked if "rails.png." exists (notice trailing ".")
+      # OS X, linux etc will return false in this case.
+      File.stubs(:exist?).with('template/../fixtures/public/images/rails.png.').returns(true)
+      assert_equal '<img alt="Rails" src="/images/rails.png?1" />', image_tag('rails.png')
+    ensure
+      ENV["RAILS_ASSET_ID"] = old_asset_id
+    end
+  end
+
   def test_timebased_asset_id
     expected_time = File.stat(File.expand_path(File.dirname(__FILE__) + "/../fixtures/public/images/rails.png")).mtime.to_i.to_s
     assert_equal %(<img alt="Rails" src="/images/rails.png?#{expected_time}" />), image_tag("rails.png")