class SimpleForm::Inputs::NumericInput

def add_size!

Rails adds the size attr by default, if the :size key does not exist. 
def add_size!
  input_html_options[:size] ||= nil
end

def input 

def input
  add_size!
  input_html_classes.unshift("numeric")
  if html5?
    input_html_options[:type] ||= "number"
    input_html_options[:step] ||= integer? ? 1 : "any"
  end
  @builder.text_field(attribute_name, input_html_options)
end