Rack middleware for pretty printing json responses and sample Rails usage

pretty_print.rb

require 'rack'

module Rack
    class PrettyPrint
        def initialize(app, options = {})
            @app, @options = app, options
        end

        def call(env)
            status, headers, response = @app.call(env)
            if headers['Content-Type'] =~ /^application\/[\w+.-]*json/ && (@options[:force_pretty] || env['QUERY_STRING'].include?("pretty=true"))
                response = [].tap do |pretty_response|
                    response.each do |chunk|
                        obj = JSON.parse chunk
                        pretty_response << JSON.pretty_unparse(obj)
                    end
                end

                headers['Content-Length'] = Rack::Utils.bytesize(response.first).to_s unless response.empty?
            end
            [status, headers, response]
        end
    end
end

rack_middleware.rb

require 'pretty_print'

Rails.configuration.middleware.insert_before ActionDispatch::ShowExceptions, Rack::PrettyPrint, force_pretty: Rails.env.development?