class Faraday::Request::Json

def body?(env)
  body = env[:body]
  case body
  when true, false
    true
  when nil
    # NOTE: nil can be converted to `"null"`, but this middleware doesn't process `nil` for the compatibility.
    false
  else
    !(body.respond_to?(:to_str) && body.empty?)
  end
end