Add a hidden_field on the file_field

This will avoid a error be raised when the only input on the form is the
`file_field`.

1 files changed, 13 insertions, 0 deletions

diff --git a/actionview/lib/action_view/helpers/tags/file_field.rb b/actionview/lib/action_view/helpers/tags/file_field.rb
index 476b820d84..02585fa0ae 100644
--- a/actionview/lib/action_view/helpers/tags/file_field.rb
+++ b/actionview/lib/action_view/helpers/tags/file_field.rb
@@ -2,6 +2,19 @@ module ActionView
   module Helpers
     module Tags # :nodoc:
       class FileField < TextField # :nodoc:
+
+        def render
+          options = @options.stringify_keys
+          if options.fetch("include_hidden", true)
+            add_default_name_and_id(options)
+            options[:type] = "file"
+            tag("input", :name => options["name"], :type => "hidden", :value => "") + tag("input", options)
+          else
+            options.delete("include_hidden")
+            @options = options
+            super
+          end
+        end
       end
     end
   end