field_error_proc and Rails Configurations

I came across something in Rails that’s fixed an issue that has seriously irked me.

Given a form in Rails:

…

Name <%= f.text_field :name %>

…

if a validation error would occur, the generated code becomes:

<p>
  <label for="user_name">Name</label>
  <div class="fieldWithErrors"><input id="user_name" name="user[name]" size="30" type="text" value="" /></div>
</p>

Which is invalid markup. I’ve constantly resorted to editing rails source in order to change the divs to spans.

Today I came across something really neat: field_proc_error. By setting this in your configuration like environment.rb, you can drastically change the output of the generated error

config.action_view.field_error_proc = Proc.new{ |html_tag, instance| "<span class=\"field_with_errors\">#{html_tag}</span>" }

Going through Trac, I see it’s been in there forever, but as usual, I’m the last one to catch it.

Awesomely useful. Thanks Rails Core.