Incompatibility with latest autoprefixer-rails

[jefmathiot]

Versions >= 9.1.4 of the autoprefixer-rails gem have deprecated therubyracer as the runtime. See https://github.com/ai/autoprefixer-rails/blob/master/lib/autoprefixer-rails/processor.rb#L149

Unfortunately, the less.rb does not seem to support the mini_racer runtime.

The workaround is to explicitely lock the autoprefixer-rails to 6.3.7. I'd be glad to submit a PR, but as the dependency has to be manually added to the Gemfiles and is not present in the gemspec, I'm not sure how I could efficiently fix the issue.

[brendon]

I think you'd have to just lock that in your own Gemfile because, as you say, it's not one of our dependencies.

[ctilley83]

Yes it is one of your dependencies.

[brendon]

autoprefixer-rails isn't one of our dependencies, but therubyracer is a development dependency in the gemspec. The only fix we could do would be to mention that specific version of autoprefixer-rails in the readme.

This gem is becoming unviable for other reasons: #53.

I think perhaps moving away from less.rb would be the proper cure. I no longer use this gem, not have the time for a fix that big, but if you want to work on a PR that moves it away from less.rb, please do :) I'm certainly happy to help review things etc...