…esh development environment :)
The problem with depending on ParseTree is that it's not supported on all platforms. dm-sweatshop for example depends on randexp and since randexp depended on ParseTree there was no way to override the platforms to use ParseTree with, in dm-sweatshop's Gemfile. dm-sweatshop indeed requires ParseTree to provide specific functionality. Depending on ParseTree explicitly in dm-sweatshop's Gemfile, means that we can limit the platforms ParseTree will be installed on by using bundler's :platform => :mri_18 option. Code in dm-sweatshop can then rescue from a LoadError from ParseTree, and will disable some features, but will still be usable.
… contributors list.