Setting rack.session to hash by default when using to_rack

[garytaylor]

In rails 7, if there is no session in the request, it now defaults to an object that responds to enabled?

However, because rack.session is set to {} in webmock (WebMock::RackResponse#session), when webmock us used in a way that mounts this rails app (using to_rack), this causes a failure in the following line in the rails app

ActionDispatch::Flash::RequestMethods#commit_flash

return unless session.enabled?

where 'session' is defined as

      def session
        fetch_header(RACK_SESSION) do |k|
          set_header RACK_SESSION, default_session
        end
      end

and fetch_header will return the session if already defined in env['rack.session'] therefore 'default_session' is not being called. The return value is therefore an empty hash which does not respond to enabled?

I am not sure if this is really a webmock issue or if rails are being a bit naughty setting rack.session to anything but a hash

[bblimke]

perhaps WebMock::RackResponse#session should return that default_session instead of returning {} ?

[jgraichen]

I have a single file test case here:

# frozen_string_literal: true

require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'

  gem 'json'
  gem 'rails', '~> 7.0'
  gem 'rspec'
  gem 'webmock'
end

ENV['RAILS_ENV'] ||= 'test'

require 'action_controller/railtie'

class Application < Rails::Application
  config.logger = Logger.new($stdout)
  Rails.logger  = config.logger

  config.action_dispatch.show_exceptions = :none

  routes.draw do
    get '/' => 'test#index'
  end
end

class TestController < ActionController::Base
  include Rails.application.routes.url_helpers

  def index
    render plain: 'Hello World'
  end
end

require 'net/http'
require 'rspec/autorun'
require 'webmock/rspec'

WebMock.enable!

RSpec.configure do |config|
  config.full_backtrace = true
end

RSpec.describe do
  it do
    stub_request(:any, /example\.org/)
      .to_rack(Rails.application)

    response = Net::HTTP.get('example.org', '/')
    expect(response).to eq 'Hello World'
  end
end

Currently, this fails:

Failures:

  1) 
     Failure/Error: response = Net::HTTP.get('example.org', '/')
     
     NoMethodError:
       undefined method `enabled?' for an instance of Hash
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/flash.rb:72:in `commit_flash'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_controller/metal.rb:253:in `dispatch'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_controller/metal.rb:335:in `dispatch'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/routing/route_set.rb:67:in `dispatch'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/routing/route_set.rb:50:in `serve'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/journey/router.rb:53:in `block in serve'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/journey/router.rb:133:in `block in find_routes'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/journey/router.rb:126:in `each'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/journey/router.rb:126:in `find_routes'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/journey/router.rb:34:in `serve'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/routing/route_set.rb:896:in `call'
     # ruby/gems/3.3.0/gems/rack-3.1.8/lib/rack/tempfile_reaper.rb:20:in `call'
     # ruby/gems/3.3.0/gems/rack-3.1.8/lib/rack/etag.rb:29:in `call'
     # ruby/gems/3.3.0/gems/rack-3.1.8/lib/rack/conditional_get.rb:31:in `call'
     # ruby/gems/3.3.0/gems/rack-3.1.8/lib/rack/head.rb:15:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/http/permissions_policy.rb:38:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/http/content_security_policy.rb:36:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/cookies.rb:704:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/callbacks.rb:31:in `block in call'
     # ruby/gems/3.3.0/gems/activesupport-7.2.1.1/lib/active_support/callbacks.rb:101:in `run_callbacks'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/callbacks.rb:30:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/executor.rb:16:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/debug_exceptions.rb:31:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/show_exceptions.rb:32:in `call'
     # ruby/gems/3.3.0/gems/railties-7.2.1.1/lib/rails/rack/logger.rb:41:in `call_app'
     # ruby/gems/3.3.0/gems/railties-7.2.1.1/lib/rails/rack/logger.rb:29:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/remote_ip.rb:96:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/request_id.rb:33:in `call'
     # ruby/gems/3.3.0/gems/rack-3.1.8/lib/rack/method_override.rb:28:in `call'
     # ruby/gems/3.3.0/gems/rack-3.1.8/lib/rack/runtime.rb:24:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/executor.rb:16:in `call'
     # ruby/gems/3.3.0/gems/actionpack-7.2.1.1/lib/action_dispatch/middleware/static.rb:27:in `call'
     # ruby/gems/3.3.0/gems/rack-3.1.8/lib/rack/sendfile.rb:114:in `call'
     # ruby/gems/3.3.0/gems/railties-7.2.1.1/lib/rails/engine.rb:535:in `call'
     # ruby/gems/3.3.0/gems/webmock-3.24.0/lib/webmock/rack_response.rb:12:in `evaluate'
     # ruby/gems/3.3.0/gems/webmock-3.24.0/lib/webmock/stub_registry.rb:80:in `evaluate_response_for_request'
     # ruby/gems/3.3.0/gems/webmock-3.24.0/lib/webmock/stub_registry.rb:67:in `response_for_request'
     # ruby/gems/3.3.0/gems/webmock-3.24.0/lib/webmock/http_lib_adapters/net_http.rb:76:in `request'
     # ruby/3.3.0/net/http.rb:2177:in `request_get'
     # ruby/3.3.0/net/http.rb:817:in `block in get_response'
     # ruby/gems/3.3.0/gems/webmock-3.24.0/lib/webmock/http_lib_adapters/net_http.rb:116:in `start_without_connect'
     # ruby/gems/3.3.0/gems/webmock-3.24.0/lib/webmock/http_lib_adapters/net_http.rb:143:in `start'
     # ruby/3.3.0/net/http.rb:816:in `get_response'
     # ruby/3.3.0/net/http.rb:803:in `get'
     # test.rb:52:in `block (2 levels) in <main>'

[jgraichen]

perhaps WebMock::RackResponse#session should return that default_session instead of returning {} ?

Does WebMock has to set a "rack.session" at all?

[bblimke]

@jgraichen possibly not. I guess the intention was to have a complete Rack app with session, in case session is not set by the app like Rails does.

[jgraichen]

@bblimke Thanks! I wasn't sure if that was intentional, e.g. to inspect the session later on.

Would it be possible not to set 'rack.session' at all? As far as I know, a rack server (such as puma) wouldn't set that either. So, if no middleware defines it (such as rails or rack-session) it should not be present.

That would help with another error I got on a Rails API-only app. It doesn't really have any sessions, but tests fail completely because any present 'rack.session' break some code, or the test instrumentation does not initialize a stub session.

I had to change the patch from above to completely strip 'rack.session' to get specs on the app passing again:

module WebmockSessionPatch
  def build_rack_env(request)
    super.tap do |env|
      env.delete('rack.session')
      env.delete('rack.session.options')
    end
  end

  WebMock::RackResponse.prepend(WebmockSessionPatch)
end

[kwstannard]

I agree with not setting session. If anyone is looking to do things as complex as sessions in their mocking, surely they can use a rack app that sets session. In the meanwhile, this is preventing utilization of Rails engines in to_rack