Question

When querying for an non-existing post in my controller via

@post = Post.find_by_id(params[:id])

I get ActiveRecord::RecordNotFound. But when I do the same in the rails console I get nil returned.

I also tried find_by_id! (note the exclamation point) that is supposed to trigger a 404, but it still just gives me ActiveRecord::RecordNotFound.

I found out that a gem could cause this kind of problem (see question: Rails Find_by_id raises exception), so my question is how do I figure out which gem that I use could cause the same problem?

This is my Gemfile

source 'https://rubygems.org'

gem 'rails', '3.2.7'
gem 'pg'
gem 'jquery-rails'
gem 'fancybox-rails', :git => 'https://github.com/sverigemeny/fancybox-rails'
gem 'bcrypt-ruby', '~> 3.0.0'
gem 'omniauth-twitter'
gem 'omniauth-facebook'
gem 'omniauth-google-oauth2'
gem 'validates_email_format_of', :git => 'git://github.com/alexdunae/validates_email_format_of.git'
gem 'cancan'
gem 'thin'
gem 'chronic'
gem 'simple_form'
gem 'twitter'
gem 'kaminari'

group :assets do
  gem 'sass-rails'
  gem 'compass-rails'
  gem 'coffee-rails'
  gem 'uglifier', '>= 1.0.3'
end

group :development do
  gem 'quiet_assets'
  gem 'faker'
end

I don’t see how I can just disable one by one until I find the Gem that might causes this problem because I will most likely trigger many other errors due to Gem dependencies in the process.

Anyone have any idea of how I should go about this?

Update
Here is the full stacktrace:

ActiveRecord::RecordNotFound in PostsController#edit

Couldn't find Post with id=123202

activerecord (3.2.7) lib/active_record/relation/finder_methods.rb:341:in `find_one'
activerecord (3.2.7) lib/active_record/relation/finder_methods.rb:312:in `find_with_ids'
activerecord (3.2.7) lib/active_record/relation/finder_methods.rb:107:in `find'
activerecord (3.2.7) lib/active_record/querying.rb:5:in `find'
cancan (1.6.8) lib/cancan/model_adapters/abstract_adapter.rb:20:in `find'
cancan (1.6.8) lib/cancan/controller_resource.rb:114:in `find_resource'
cancan (1.6.8) lib/cancan/controller_resource.rb:68:in `load_resource_instance'
cancan (1.6.8) lib/cancan/controller_resource.rb:32:in `load_resource'
cancan (1.6.8) lib/cancan/controller_resource.rb:25:in `load_and_authorize_resource'
cancan (1.6.8) lib/cancan/controller_resource.rb:10:in `block in add_before_filter'
activesupport (3.2.7) lib/active_support/callbacks.rb:418:in `_run__4208450199150212965__process_action__1027836660135587880__callbacks'
activesupport (3.2.7) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.7) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
activesupport (3.2.7) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.7) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.2.7) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (3.2.7) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.2.7) lib/active_support/notifications.rb:123:in `block in instrument'
activesupport (3.2.7) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (3.2.7) lib/active_support/notifications.rb:123:in `instrument'
actionpack (3.2.7) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.2.7) lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
activerecord (3.2.7) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.7) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.7) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.7) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.7) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.7) lib/action_controller/metal.rb:246:in `block in action'
actionpack (3.2.7) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.7) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.7) lib/action_dispatch/routing/route_set.rb:36:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.7) lib/action_dispatch/routing/route_set.rb:600:in `call'
omniauth (1.1.1) lib/omniauth/strategy.rb:177:in `call!'
omniauth (1.1.1) lib/omniauth/strategy.rb:157:in `call'
omniauth (1.1.1) lib/omniauth/strategy.rb:177:in `call!'
omniauth (1.1.1) lib/omniauth/strategy.rb:157:in `call'
omniauth (1.1.1) lib/omniauth/strategy.rb:177:in `call!'
omniauth (1.1.1) lib/omniauth/strategy.rb:157:in `call'
omniauth (1.1.1) lib/omniauth/builder.rb:48:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.3) lib/rack/etag.rb:23:in `call'
rack (1.4.3) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.3) lib/rack/session/abstract/id.rb:210:in `context'
rack (1.4.3) lib/rack/session/abstract/id.rb:205:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/cookies.rb:338:in `call'
activerecord (3.2.7) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.7) lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
activesupport (3.2.7) lib/active_support/callbacks.rb:405:in `_run__503554315877740465__call__403817388267166975__callbacks'
activesupport (3.2.7) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.7) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.7) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.7) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/reloader.rb:65:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.7) lib/rails/rack/logger.rb:26:in `call_app'
railties (3.2.7) lib/rails/rack/logger.rb:16:in `call'
quiet_assets (1.0.1) lib/quiet_assets.rb:20:in `call_with_quiet_assets'
actionpack (3.2.7) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.3) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.3) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.7) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.3) lib/rack/lock.rb:15:in `call'
actionpack (3.2.7) lib/action_dispatch/middleware/static.rb:62:in `call'
railties (3.2.7) lib/rails/engine.rb:479:in `call'
railties (3.2.7) lib/rails/application.rb:220:in `call'
rack (1.4.3) lib/rack/content_length.rb:14:in `call'
railties (3.2.7) lib/rails/rack/log_tailer.rb:17:in `call'
thin (1.5.0) lib/thin/connection.rb:81:in `block in pre_process'
thin (1.5.0) lib/thin/connection.rb:79:in `catch'
thin (1.5.0) lib/thin/connection.rb:79:in `pre_process'
thin (1.5.0) lib/thin/connection.rb:54:in `process'
thin (1.5.0) lib/thin/connection.rb:39:in `receive_data'
eventmachine (1.0.0) lib/eventmachine.rb:187:in `run_machine'
eventmachine (1.0.0) lib/eventmachine.rb:187:in `run'
thin (1.5.0) lib/thin/backends/base.rb:63:in `start'
thin (1.5.0) lib/thin/server.rb:159:in `start'
rack (1.4.3) lib/rack/handler/thin.rb:13:in `run'
rack (1.4.3) lib/rack/server.rb:268:in `start'
railties (3.2.7) lib/rails/commands/server.rb:70:in `start'
railties (3.2.7) lib/rails/commands.rb:55:in `block in <top (required)>'
railties (3.2.7) lib/rails/commands.rb:50:in `tap'
railties (3.2.7) lib/rails/commands.rb:50:in `<top (required)>'
script/rails:6:in `require'
script/rails:6:in `<main>'

Answer 1

As drewinglis pointed out, this is caused by cancan.

Cancan loads the post to determine whether the user has authorisation to perform whatever action on it. If the post is not found, it will respond with a 404, ActiveRecord::RecordNotFound.

Here, Ryan goes into the reasoning behind this a little: https://github.com/ryanb/cancan/issues/43 he also suggests rescuing from the 404 if that’s not the behaviour you require.