Issue #8297 has been updated by nobu (Nobuyoshi Nakada).

Description updated


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Bug #8297: extend & inherited class variable issue
https://bugs.ruby-lang.org/issues/8297#change-38757

Author: dunric (David Unric)
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 
ruby -v: 2.0.0p0
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


=begin
By the current documentation, (({Object#extend})) method has to (only) add instance methods of a module given as a parameter.
In the following example, the class ((|C|)) is extended with module ((|M|)).
By (({class_variables})) method sent to singleton class of C also did inherit class variable ((|@@xyz|)).
However when inherited ((|@@xyz|)) is accessed, (({NameError})) exception is raised as it is was not initialized.

  module M
    @@xyz = 123
  end
  M.class_variables    # [:@@xyz]
  M.class_variable_get :@@xyz    # 123 , so far so good

  class C
    extend M
  end
  p C.singleton_class.class_variables    # [:@@xyz]
  p C.singleton_class.class_variable_get :@@xyz # NameError exception

Either (({class_variables})) returns invalid array - ie. ((|@@xyz|)) was not inherited at all or (({class_variable_get})) ignores class variables inherited from module (when sent to a singleton).
=end
Prior Ruby versions like 1.9.3p392 does not suffer this issue as return with Module#class_variables returns an empty array.



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