class ActionView::LookupContext

def with_layout_format

A method which only uses the first format in the formats array for layout lookup. 
def with_layout_format
  if formats.size == 1
    yield
  else
    old_formats = formats
    _set_detail(:formats, formats[0,1])
    begin
      yield
    ensure
      _set_detail(:formats, old_formats)
    end
  end
end