Sinatra + Heroku Session Bug

Readme.md

When using Sinatra on Heroku, you can set your app up in such a way as to have a bug where your sessions will work locally but not on Heroku. The bug arises when you have the lines enable :sessions and use Rack::Session::Cookie both in your app. The solution I found was to remove the line enable :sessions.

config.ru

require "bundler/setup"
require 'sinatra'

get '/a' do
  to_display = session[:to_remember]
  session[:to_remember] = "a"
  to_display
end

get '/b' do
  to_display = session[:to_remember]
  session[:to_remember] = "b"
  to_display
end

enable :sessions # <-- this line will cause it to work locally but not on Heroku, just delete it.
use Rack::Session::Cookie
run Sinatra::Application

Gemfile

source "http://rubygems.org"
gem "sinatra"

Gemfile.lock

GEM
  remote: http://rubygems.org/
  specs:
    rack (1.3.0)
    sinatra (1.2.6)
      rack (~> 1.1)
      tilt (< 2.0, >= 1.2.2)
    tilt (1.3.2)

PLATFORMS
  ruby

DEPENDENCIES
  sinatra

This was a life saver for me. Seems like use Rack::Session::Cookie and enable :sessions don't play well together in general.

enable :sessions turns on a bunch more options, but by default also does Rack::Session::Cookie. It's mostly authentication options (which you should look into).