module ActiveSupport::Deprecation::DeprecatedConstantAccessor

constant with the same name. This is an unsupported edge case.
for example, if an ancestor of the enclosing namespace has a
called and the deprecation won't work as intended. This may happen,
namespace and Ruby constant lookup finds it, the hook won't be
Caveat: If the deprecated constant name is reachable in a different

message and constantizes the replacement.
code references the deprecated constant, the callback prints the
For this to work, a +const_missing+ hook is installed. When client

argument.
The message can be customized with the optional +message+ keyword

(called from ...)
DEPRECATION WARNING: A::B is deprecated! Use C::D instead.

evaluate to C::D now, and trigger a deprecation warning:
With that in place, references to A::B still work, they

deprecation message, an instance of ActiveSupport::Deprecation.
The +deprecator+ keyword argument is the object that will print the

In both cases, strings and symbols are supported.

namespace as the deprecated one was.
has to be a full path even if the replacement is defined in the same
The second argument is the constant path of the replacement. That

the constant you want to deprecate in the enclosing class or module.
The first argument is a constant name (no colons). It is the name of

end
deprecate_constant "B", "C::D", deprecator: ActiveSupport::Deprecation.new

include ActiveSupport::Deprecation::DeprecatedConstantAccessor
module A

require "active_support/deprecation"

definition of A::B and declare the deprecation in +A+:
In order to rename A::B to C::D, you need to delete the

deprecation message.
both the old and new names work, but using the old one prints a
Provides a way to rename constants with a deprecation cycle in which

def deprecate_constant(old_constant_name, new_constant_path, deprecator:, message: nil)
  class_variable_set(:@@_deprecated_constants, {}) unless class_variable_defined?(:@@_deprecated_constants)
  class_variable_get(:@@_deprecated_constants)[old_constant_name.to_s] = { new: new_constant_path, message: message, deprecator: deprecator }
end