Allow to force custom headers for responses that shouldn't include them

[jodosha]

According to RFC 2616, when a response MUST have an empty body, it only allows Entity Headers.

For instance, a 204 doesn't allow Content-Type or any other custom header.

This restriction is enforced by Lotus::Action::Head#finish.

However, there are cases that demand to bypass this rule to set meta
informations via headers.

An example is a DELETE request for a JSON API application. It returns a 204 but still wants to specify the rate limit quota via X-Rate-Limit.

require 'lotus/controller'

module Books
  class Destroy
    include Lotus::Action

    def call(params)
      # ...
      self.headers.merge!(
        'Last-Modified' => 'Fri, 27 Nov 2015 13:32:36 GMT',
        'X-Rate-Limit'  => '4000',
        'Content-Type'  => 'application/json',
        'X-No-Pass'     => 'true'
      )

      self.status = 204
    end

    private

    def keep_response_header?(header)
      super || header == 'X-Rate-Limit'
    end
  end
end

Only the following headers will be sent:

• Last-Modified - because we used `super' in the method that respects the HTTP RFC
• X-Rate-Limit - because we explicitely allow it

Both Content-Type and X-No-Pass are removed because they're not allowed

If there are no objections, I would release v0.4.6 with only this change, because needed by a project I'm working on.

/cc @lotus/core-team

[AlfonsoUceda]

space between { and |

[AlfonsoUceda]

👍

[runlevel5]

@jodosha 👍