Add a 'report only' feature where activerecord models will not blow up when firewalled but will just log

[JackMc]

Currently, the gem will always blow up when a firewalled constraint is violated. This isn’t great for when you’re trying to implement this new safeguard in a production application.

This adds an option to firewalled_belongs_to called report_only that instead of raising the exception will print out the error message to the log at the INFO level.

I also added an “image” model & association to each user which uses the report only type of belongs to.

[JackMc]

These two helpers are copied & modified from an internal helper in ActionView: https://github.com/rails/rails/blob/309bb6c4d068b0d480681cf4ef1b90158527dfe5/actionview/test/template/digestor_test.rb#L304-L317

[JackMc]

This is good for review now (no longer WIP)

[rafaelfranca]

We don't need to depend on rails. This gem seems to depend only on activerecord and activesupport.

[JackMc]

Hey, I tried to switch to just these as dependencies and I get this error from running bin/test:

bin/test:5:in `require': cannot load such file -- rails/plugin/test (LoadError)
	from bin/test:5:in `<main>'

I figure this is from not having railties, which if I add that then gives me this error:

/Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/railtie/configuration.rb:95:in `method_missing': undefined method `action_mailer' for #<Rails::Application::Configuration:0x00007f91c6190258> (NoMethodError)
	from /Users/jackmc/src/github.com/Shopify/activerecord-firewall/test/dummy/config/environments/test.rb:30:in `block in <top (required)>'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/railtie.rb:211:in `instance_eval'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/railtie.rb:211:in `configure'
	from /Users/jackmc/src/github.com/Shopify/activerecord-firewall/test/dummy/config/environments/test.rb:1:in `<top (required)>'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:292:in `require'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:292:in `block in require'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:258:in `load_dependency'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/activesupport-5.1.7/lib/active_support/dependencies.rb:292:in `require'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/engine.rb:600:in `block (2 levels) in <class:Engine>'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/engine.rb:599:in `each'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/engine.rb:599:in `block in <class:Engine>'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/initializable.rb:30:in `instance_exec'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/initializable.rb:30:in `run'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/initializable.rb:59:in `block in run_initializers'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:228:in `block in tsort_each'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:422:in `block (2 levels) in each_strongly_connected_component_from'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:431:in `each_strongly_connected_component_from'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:421:in `block in each_strongly_connected_component_from'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/initializable.rb:48:in `each'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/initializable.rb:48:in `tsort_each_child'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:415:in `call'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:415:in `each_strongly_connected_component_from'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:349:in `block in each_strongly_connected_component'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:347:in `each'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:347:in `call'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:347:in `each_strongly_connected_component'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:226:in `tsort_each'
	from /opt/rubies/2.4.2/lib/ruby/2.4.0/tsort.rb:205:in `tsort_each'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/initializable.rb:58:in `run_initializers'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/application.rb:353:in `initialize!'
	from /Users/jackmc/src/github.com/Shopify/activerecord-firewall/test/dummy/config/environment.rb:5:in `<top (required)>'
	from /Users/jackmc/src/github.com/Shopify/activerecord-firewall/test/test_helper.rb:3:in `require'
	from /Users/jackmc/src/github.com/Shopify/activerecord-firewall/test/test_helper.rb:3:in `<top (required)>'
	from /Users/jackmc/src/github.com/Shopify/activerecord-firewall/test/activerecord/firewall_test.rb:1:in `require'
	from /Users/jackmc/src/github.com/Shopify/activerecord-firewall/test/activerecord/firewall_test.rb:1:in `<top (required)>'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/test_unit/runner.rb:50:in `require'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/test_unit/runner.rb:50:in `block in load_tests'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/test_unit/runner.rb:50:in `each'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/test_unit/runner.rb:50:in `load_tests'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/test_unit/runner.rb:39:in `run'
	from /Users/jackmc/.gem/ruby/2.4.2/gems/railties-5.1.7/lib/rails/plugin/test.rb:7:in `<top (required)>'
	from bin/test:5:in `require'
	from bin/test:5:in `<main>'

[rafaelfranca]

That second error is because your dummy app is using action mailer in the configs. You can remove it .

[JackMc]

I pulled the commit that had rubocop & style changes. I'll add this in a separate PR to keep the diff clear