module ActiveSupport::DescendantsTracker

def clear(classes) # :nodoc:
  raise "DescendantsTracker.clear was disabled because config.enable_reloading is false" if @clear_disabled
  classes.each do |klass|
    @excluded_descendants << klass
    klass.descendants.each do |descendant|
      @excluded_descendants << descendant
    end
  end
end

def descendants(klass)
  klass.descendants
end

def descendants
  subclasses = DescendantsTracker.reject!(self.subclasses)
  subclasses.concat(subclasses.flat_map(&:descendants))
end

def disable_clear! # :nodoc:
  unless @clear_disabled
    @clear_disabled = true
    ReloadedClassesFiltering.remove_method(:subclasses)
    ReloadedClassesFiltering.remove_method(:descendants)
    @excluded_descendants = nil
  end
end

def reject!(classes) # :nodoc:
  if @excluded_descendants
    classes.reject! { |d| @excluded_descendants.include?(d) }
  end
  classes
end

def subclasses(klass)
  klass.subclasses
end