openproject/app/models/report/inherited_namespace.rb

module Report::InheritedNamespace
  NESTED_NAMESPACES = %w[Validation Filter GroupBy Result Operator QueryUtils]

  module Hook
    def const_missing(name, *)
      super
    rescue NameError => error
      load_constant name, error
    end
  end

  def self.activate
    Report.extend self
    NESTED_NAMESPACES.each { |n| n.extend self }
  end

  def inherited(klass)
    super
    propagate klass
  end

  def included(klass)
    super
    propagate klass
  end

  def propagate(klass)
    klass.extend Report::InheritedNamespace
    klass.extend Hook
    return unless klass < Report
    NESTED_NAMESPACES.each do |name|
      if file = ActiveSupport::Dependencies.search_for_file("#{klass.name}::#{name}".underscore)
        require_or_load file
        propagate klass.const_get(name)
      else
        const_missing name
      end
    end
  end

  def load_constant(name, error = NameError)
    zuper = (Class === self ? superclass : ancestors.second).const_get(name)
    klass = case zuper
    when Class  then const_set name, Class.new(zuper)
    when Module then const_set name, Module.new { include zuper }
    else const_set name, zuper
    end
    propagate klass
    klass
  rescue NameError, ArgumentError => new_error
    if file = ActiveSupport::Dependencies.search_for_file("#{self.name}::#{name}".underscore)
      require_or_load file
      const_get name
    else
      error.message << "\n\tWas #{new_error.class}: #{new_error.message}"
      new_error.backtrace[0..9].each { |l| error.message << "\n\t\t#{l}" }
      error.message << "\n\t\t..." if new_error.backtrace.size > 10
      raise error
    end
  end
end