“...I've been working since 2008 with Ruby / Ruby on Rails, love a bit of Elixir / Phoenix and learning Rust. I also poke through other people's code and make PRs for OpenSource Ruby projects that sometimes make it. Currently working for InPay...”

Rob Lacey
Senior Software Engineer, UK

Assignment still proceeds even with undefined local variable or method

This week I had a really horrible bug. One spec in our suite in our CI knocked out every subsequent spec after skipping. The spec works in isolation. just not on CI and not in a full suite run.

RSpec.shared_contexts 'with some feature' do
  skip('This is not available on CI') if ENV['CI']
  original_driver = Capybara.javascript_driver

  Capybara.javascript_driver = :something_else
ensure
  Capybara.javascript_driver  = original_driver
end

RSpec.describe 'something' do
  include_context 'with some feature'
  it do
    visit '/'
  end
end

Turns out our Capybara.javascript_driver ended up being nil, and our test suite fell over because CI doesn’t support non-headless Chrome. And the reason…

I would appear that variable assignment in Ruby still assigns nil if we attempt to assign a variable from another variable or method that is undefined.

irb(main):001> a = some_method_or_var_that_is_not_defined
(irb):1:in `<main>': undefined local variable or method `some_method_or_var_that_is_not_defined' for main (NameError)

a = some_method_or_var_that_is_not_defined
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	from <internal:kernel>:187:in `loop'
	from /Users/rl/.asdf/installs/ruby/3.3.0/lib/ruby/gems/3.3.0/gems/irb-1.14.0/exe/irb:9:in `<top (required)>'
	from /Users/rl/.asdf/installs/ruby/3.3.0/bin/irb:25:in `load'
	from /Users/rl/.asdf/installs/ruby/3.3.0/bin/irb:25:in `<main>'
irb(main):002> a
=> nil

Who knew? I didn’t.

GPK of the Day Slain WAYNE