Ryan Bigg

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Code doesn't protect against stupid

06 Mar 2011

Herein lies a tale of woe, heartache and eventual triumph over stupidity.

I've been developing forum engine for the past week or so as part of my research for the engines chapter on Rails 3 in Action. It's been an interesting experience.

This afternoon, I was contacted by Adam McDonald who's working with me on it as part of a learning exercise for him and free labour for myself. He asked questions about how to get the engine running so that he could see it and I told him to run bundle exec rails s and go to http://localhost:3000/forem. Only one of those two things worked. So I told him to instead just run the tests and I'd take a look at the issue later on, as I was completing Chapter 13 of the book.

So now (actually, just previous to this post) I remembered the issue and tried it myself. It was still broken! This was simply because we didn't have a root route defined in the routes file, like this commit adds. So I added one.

Then I saw uninitialized constant Forem::ForumsController.

WHAT?! How dare code be broken on my watch! The tests passed, so this code had absolutely no reason to be broken. I thought it may have been because the engine wasn't loading the controllers in that special mode of bundle exec rails s. It turns out I was almost right.

So I got hacky and ended up doing a require ENGINE_ROOT + "app/controllers/forem/forums_controller" which just didn't work. I checked that ENGINE_ROOT + "app/controllers/forem" was indeed the right path by using File.expand_path and then copy+pasting it to the command line and cd'ing into the directory. That god damned file was there.

A moment of swearing took place where I ranted in IRC and to Adam about the lack of documentation on engines making things impossible.

Then when I calmed down, I went back into the console and saw this.

Only one l

The well-trained eye (not mine) would see quite immediately that forums_controler.rb is missing an l.

So why did this work in the first place?

Oh my God. I was stunned. How could I be so stupid? I corrected it and sure enough the route worked. Major "oh durr" moment was had.

This has worked all this time because I've been running only the tests (bundle exec rspec spec, for the curious), which run in the test environment. This environment dutifully duplicates the production environment habit of loading all the files in app/**/*, regardless of the names. That way when requests are made to the application, it doesn't need to go looking for the files containing the right classes; everything should (and is) loaded by that point.

When I run bundle exec rails s, Rails starts up in development mode instead! When we make a request to a route, Rails will go looking for the proper controller (in this case, app/controllers/forem/forums_controller.rb, with TWO l's) and if it can't find it then it will scream at you, claiming that you treated it wrong.

Well, that was a fun experience. I don't think I'll ever do that again and I'll be checking the dark corners of my applications for this little furry beast.

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