When split cookie is a valid, json encoded String, a NoMethodError is raised

[knarewski]

Describe the bug
When split cookie is a valid, json encoded String, a NoMethodError is raised.

To Reproduce
Steps to reproduce the behavior:

1. Save the following script as test.rb

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'split'
  gem 'sinatra'
  gem 'sinatra-contrib'
  gem 'redis', '~> 4.8'
end

Split.configure do |config|
  config.persistence = :cookie
  config.experiments = { foo: { alternatives: ['a', 'b'] } }
end

class MySinatraApp < Sinatra::Base
  helpers Sinatra::Cookies
  helpers Split::Helper

  get '/' do
    ab_test(:foo)
  end
end

MySinatraApp.run!

2. Run: ruby test.rb
3. On a separate terminal window, invoke curl -H "User-Agent: not-a-bot" -H 'Cookie: split="valid-json-string"' localhost:4567
4. See the app crashing with NoMethodError - undefined method `keys' for "valid-json-string":String

Expected behavior
The invalid content is ignored, similarly to how unparseable JSON is ignored

Additional context
The trivial check in cookie_adapter.rb works for me:

              parsed = JSON.parse(cookies)
              parsed.is_a?(String) ? {} : parsed

I'm happy to submit a PR if desired

[andrehjr]

Hi @knarewski! Thanks for the issue and the repro!

Please send a PR 🎉 We should also protect it against other types. if JSON.parse returns anything other than a Hash, split wouldn't know how to handle it.

An integer would also break:

curl -H "User-Agent: not-a-bot" -H 'Cookie: split=1' localhost:4567

If I remember correctly, this issue should happens with json >= 2.0. Because the behavior of JSON.parse changed.

[knarewski]

Hi @andrehjr ! Thank you for such a swift response 🚀 ! I prepared a fix, but it's blocked by an unrelated CI failure. I'm happy to submit a PR once the CI fix is merged: #696