I Updated Rails. Now Everything's on Fire.

Nate Vick - June 03, 2019

Following up on my best practices post, I have a prime example of one common issue that surfaces when upgrading a Rails app.

I decided to spike on upgrading a small internal app to Rails 6.0.0.rc1. The test suite is green on Rails 5.2.3 and Ruby 2.6.2, so I bumped the Rails version in the Gemfile.

source '<https://rubygems.org>'
git_source(:github) { |repo| "<https://github.com/#{repo}.git>" }

ruby '2.6.2'

gem 'rails', '6.0.0.rc1'

In the terminal, I ran bundle update rails and it updated without issue (I mentioned this is a small app, right?). Even on small apps, this should make you raise an eyebrow.

Skeptically, I ran the test suite.

Errors all the way down.

An error occurred while loading ./spec/services/step_processor_spec.rb.
Failure/Error: require File.expand_path('../../config/environment', __FILE__)

TypeError:
  Rails::SourceAnnotationExtractor is not a class/module
# /gems/gems/haml-rails-1.0.0/lib/haml-rails.rb:49:in `block in <class:Railtie>'
# ...more output...

Finished in 0.00027 seconds (files took 1.41 seconds to load)
0 examples, 0 failures, 17 errors occurred outside of examples

Based on the error, let's take a look at haml-rails and SourceAnnotationExtractor in Rails to see what changed and if there is a newer version of haml-rails.

But wait. You may ask: "Why not try upgrading the gem and move on?". Taking the time to understand the root cause of a problem provides confidence in the solution and clear direction to resolve broader symptoms throughout the codebase.

Taking the time to understand the root cause of a problem provides confidence in the solution and clear direction to resolve broader symptoms throughout the codebase.

Here is line 49 in lib/haml-rails.rb:

SourceAnnotationExtractor::Annotation.register_extensions('haml') do |tag|

Sure enough, there is a change in Rails 6 that moves SourceAnnotationExtractor to Rails::SourceAnnotationExtractor (PR #32065). The top-level class has been deprecated, but the deprecation warning does not apply to the sub-classes which raise the TypeError.

Knowing the source of the error, we can check if there is a newer version of haml-rails compatible with Rails 6. Again, you will find value by not just upgrading the gem, but understanding the changes in the newer versions. With haml-rails, there is a newer version that has a fix for the issue. By bumping up to that version, I'm able to run the test suite without errors and get back to the upgrade at hand.

Schedule a quick call with me to see how our expertise can keep your team delivering features during your Rails upgrade.

Nate Vick

Nate is our COO and keeps the wheels turning, so to speak. In his free time he enjoys spending time with his wife and kids, hiking, and exploring new technology.

  
  

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