require "active_support/inflector/methods" module ActiveSupport class Deprecation # DeprecatedConstantAccessor transforms a constant into a deprecated one by # hooking +const_missing+. # # It takes the names of an old (deprecated) constant and of a new constant # (both in string form) and optionally a deprecator. The deprecator defaults # to +ActiveSupport::Deprecator+ if none is specified. # # The deprecated constant now returns the same object as the new one rather # than a proxy object, so it can be used transparently in +rescue+ blocks # etc. # # PLANETS = %w(mercury venus earth mars jupiter saturn uranus neptune pluto) # # (In a later update, the original implementation of `PLANETS` has been removed.) # # PLANETS_POST_2006 = %w(mercury venus earth mars jupiter saturn uranus neptune) # include ActiveSupport::Deprecation::DeprecatedConstantAccessor # deprecate_constant 'PLANETS', 'PLANETS_POST_2006' # # PLANETS.map { |planet| planet.capitalize } # # => DEPRECATION WARNING: PLANETS is deprecated! Use PLANETS_POST_2006 instead. # (Backtrace information…) # ["Mercury", "Venus", "Earth", "Mars", "Jupiter", "Saturn", "Uranus", "Neptune"] module DeprecatedConstantAccessor def self.included(base) extension = Module.new do def const_missing(missing_const_name) if class_variable_defined?(:@@_deprecated_constants) if (replacement = class_variable_get(:@@_deprecated_constants)[missing_const_name.to_s]) replacement[:deprecator].warn(replacement[:message] || "#{name}::#{missing_const_name} is deprecated! Use #{replacement[:new]} instead.", caller_locations) return ActiveSupport::Inflector.constantize(replacement[:new].to_s) end end super end def deprecate_constant(const_name, new_constant, message: nil, deprecator: ActiveSupport::Deprecation.instance) class_variable_set(:@@_deprecated_constants, {}) unless class_variable_defined?(:@@_deprecated_constants) class_variable_get(:@@_deprecated_constants)[const_name.to_s] = { new: new_constant, message: message, deprecator: deprecator } end end base.singleton_class.prepend extension end end end end