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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
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