Active Record Arel DepthFirst Visitor

This gem re-introduces Arel code that was removed from Rails 6.1: rails/rails#36492 . The code existed in the arel gem from 4.0.0 to 9.0.0, and the rails gem from 4.0.0 to 6.0.0.

It provides a DepthFirst visitor for Arel that allows you to traverse the Arel AST, e.g. for visualizations.

Include this gem into your Gemfile:

gem 'activerecord-arel_depth_first'

This visitor makes the Arel AST enumerable, so you can do a depth-first iteration over it:

User.some_arbitrary_scope.arel.ast.each do |node|
  case node
  when Arel::Table
    # do something for table nodes
  when Arel::Nodes::Equality
    # do something for equality nodes
  else 
    # and so on ...
  end
end

activerecord-arel_depth_first is released under the MIT License.