Deface caught in endless loop when processing a certain constellation

[scan]

We've just had a lot of trouble solving a problem with the Rails Server and Rails Console caught in a loop, not even reacting to SigTerm. After quite a while of trying out different combinations of Gems and Ruby versions, I was able to finally find the solution to lie in Deface.

During development, we added out own stylesheet to the spree head, in /app/overrides/spree/shared/_head/add_stylesheet.html.haml.deface. In the meantime, to do a comparison, the new stylesheet was commented out, which then led to the dev server not reacting and the process taking up 100% of CPU time. It looked like this:

//
    replace 'erb[loud]:contains("stylesheet_link_tag")'
    original '558b22855bf0d0e777aeaa1a8cbb51e628870834'

//= stylesheet_link_tag 'application', media: :screen

Trying to find out why, I was able to get Ruby to react to SigTerm at one point, and that led me to the process hanging in line L108 of lib/deface/dsl/loader.rb. It looks like deface has a problem removing the commented line and is caught in the loop.

Using deface 1.0.2, rubygems release.