Print the Rails controller inheritance tree

print_controller_tree.rb

#!/usr/bin/env ruby

require File.expand_path('../../config/environment', __FILE__)

Rails.application.eager_load!

def build_tree(branch, ancestors)
  return if ancestors.empty?

  first, *tail = *ancestors

  branch[first] ||= {}

  build_tree(branch[first], tail)
end

def print_tree_indented(branch, depth=0)
  return if branch.empty?

  indent = '    ' * depth

  branch.sort_by { |(k,v)| k.name }.each_with_index do |(name, sub_branch), index|
    puts "#{indent}#{name}"
    print_tree_indented(sub_branch, depth+1)
  end
end

def print_tree(branch, indent = '', top_level: true)
  return if branch.empty?

  branch.sort_by { |(k,v)| k.name }.each_with_index do |(name, sub_branch), index|
    last_item = (index == branch.size-1)
    stopper = (last_item ? '  └ ' : '  ├ ') unless top_level

    puts "#{indent}#{stopper}#{name}"

    new_indent = (last_item ? '    ' : '  │ ') unless top_level
    print_tree(sub_branch, "#{indent}#{new_indent}", top_level: false)
  end
end

def skip_controller?(controller)
  # Customise which controllers get added to the tree.
  false
end

all_controllers = ObjectSpace.each_object(Class).select do |klass|
  klass.respond_to?(:name) && klass.name&.end_with?('Controller')
end

tree = all_controllers.each_with_object({}) do |controller, memo|
  ancestors = (controller.ancestors & all_controllers).reverse
  ancestors.unshift(ancestors.first.superclass)

  next if skip_controller?(controller)

  build_tree(memo, ancestors)
end

print_tree(tree)