nil error in extends() method using Rails 4

[frayzhe]

I was getting an error in nestive while upgrading a Rails 3.2 app to 4.0, so I created a very simple blog app to test:

rails new Blog ; cd Blog
rails generate scaffold post title:string body:text
rake db:migrate

I updated the application.html.erb layout to match the nestive example, added the blog layout, updated app/views/posts/index.html.erb to follow the example, and updated the PostsController to use the new blog layout. When I try to visit the posts#index page, I get the following error:

nestive (0.4.0) app/helpers/nestive/layout_helper.rb:92:in `extends'
app/views/layouts/blog.html.erb:1:in `_app_views_layouts_blog_html_erb__2118491034999130098_70363411807260'
actionpack (4.0.0) lib/action_view/template.rb:143:in `block in render'
...

This is the same error I was getting with my app. It looks like the call to content_for(:layout) is returning nil. Not sure what's going on or how to debug further, but the original code I was testing worked fine with nestive and Rails 3.2.

[frayzhe]

FYI, I tested this with Ruby 2.0.0 (p247) and 1.9.3 (p448) and ran into the same problem with both.

[rwz]

It'd be nice if you actually include a traceback of the error or steps to reproduce. Or even share you example app with instructions of how to trigger the error. That'd be the best.

[frayzhe]

I've included the full trace below. When you say "share your example app", I'm assuming you mean publicly somewhere. I don't really have an easy way to do that, other than going through the hoops to host the test app on something like Heroku. I literally did the three steps above plus copying the steps in the nestive example, so I'm hoping that's enough to let you reproduce it (or let me know that it works for you so I can figure out why it fails for me).

nestive (0.4.0) app/helpers/nestive/layout_helper.rb:92:in `extends'
app/views/layouts/blog.html.erb:1:in `_app_views_layouts_blog_html_erb__3284810478285402737_70143336896800'
actionpack (4.0.0) lib/action_view/template.rb:143:in `block in render'
activesupport (4.0.0) lib/active_support/notifications.rb:161:in `instrument'
actionpack (4.0.0) lib/action_view/template.rb:141:in `render'
actionpack (4.0.0) lib/action_view/renderer/template_renderer.rb:61:in `render_with_layout'
actionpack (4.0.0) lib/action_view/renderer/template_renderer.rb:47:in `render_template'
actionpack (4.0.0) lib/action_view/renderer/template_renderer.rb:17:in `render'
actionpack (4.0.0) lib/action_view/renderer/renderer.rb:42:in `render_template'
actionpack (4.0.0) lib/action_view/renderer/renderer.rb:23:in `render'
actionpack (4.0.0) lib/abstract_controller/rendering.rb:127:in `_render_template'
actionpack (4.0.0) lib/action_controller/metal/streaming.rb:219:in `_render_template'
actionpack (4.0.0) lib/abstract_controller/rendering.rb:120:in `render_to_body'
actionpack (4.0.0) lib/action_controller/metal/rendering.rb:33:in `render_to_body'
actionpack (4.0.0) lib/action_controller/metal/renderers.rb:26:in `render_to_body'
actionpack (4.0.0) lib/abstract_controller/rendering.rb:97:in `render'
actionpack (4.0.0) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
activesupport (4.0.0) lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
/Users/dustin/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/benchmark.rb:296:in `realtime'
activesupport (4.0.0) lib/active_support/core_ext/benchmark.rb:12:in `ms'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:41:in `block in render'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
activerecord (4.0.0) lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:40:in `render'
actionpack (4.0.0) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (4.0.0) lib/action_controller/metal/implicit_render.rb:5:in `send_action'
actionpack (4.0.0) lib/abstract_controller/base.rb:189:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (4.0.0) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (4.0.0) lib/active_support/callbacks.rb:393:in `_run__1190728803820931505__process_action__callbacks'
activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.0) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.0.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
activerecord (4.0.0) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (4.0.0) lib/abstract_controller/base.rb:136:in `process'
actionpack (4.0.0) lib/abstract_controller/rendering.rb:44:in `process'
actionpack (4.0.0) lib/action_controller/metal.rb:195:in `dispatch'
actionpack (4.0.0) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.0.0) lib/action_controller/metal.rb:231:in `block in action'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `call'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:48:in `call'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:71:in `block in call'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:655:in `call'
rack (1.5.2) lib/rack/etag.rb:23:in `call'
rack (1.5.2) lib/rack/conditionalget.rb:25:in `call'
rack (1.5.2) lib/rack/head.rb:11:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/flash.rb:241:in `call'
rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/cookies.rb:486:in `call'
activerecord (4.0.0) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
activerecord (4.0.0) lib/active_record/migration.rb:369:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.0) lib/active_support/callbacks.rb:373:in `_run__1091337090597437586__call__callbacks'
activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `block in call'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.0.0) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/static.rb:64:in `call'
railties (4.0.0) lib/rails/engine.rb:511:in `call'
railties (4.0.0) lib/rails/application.rb:97:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
/Users/dustin/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
/Users/dustin/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
/Users/dustin/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'

[rwz]

When you say "share your example app", I'm assuming you mean publicly somewhere. I don't really have an easy way to do that, other than going through the hoops to host the test app on something like Heroku.

Well, why can't you just put it on github?

[frayzhe]

Certainly! It's here: https://github.com/frayzhe/nestive-test

[rwz]

Ok, I got the bug. This is pretty strange though that I've never seen anything like that before.

[rwz]

Fixed and released version 0.5. Thanks for reporting the bug!

[frayzhe]

Thanks for the fix!