Issue #7844 has been updated by matz (Yukihiro Matsumoto).


I believe the behavior is undefined (or implementation defined) when module dependency has contradiction.
And preferably error should be raised when contradiction detected.

Matz.

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Bug #7844: include/prepend satisfiable module dependencies are not satisfied
https://bugs.ruby-lang.org/issues/7844#change-36235

Author: mame (Yusuke Endoh)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: 
Target version: next minor
ruby -v: ruby 2.0.0dev (2013-02-13 trunk 39225) [x86_64-linux]


Hello,

  module P
    def m; puts "P"; super; end
  end
  module Q
    def m; puts "Q"; super; end
    include P
  end
  module R
    def m; puts "R"; super; end
    prepend Q
  end
  module S
    def m; puts "S"; super; end
    include R
  end
  class A
    def m; puts "A"; super; end
    prepend P
    include S
  end
  A.new.m #=> P, R, A, S, Q

This code has five module dependencies, but only two are satisfied.

- Q includes P, which is not satisfied: P#m precedes Q#m.
- R prepends Q, which is not satisfied: R#m precedes Q#m.
- S includes R, which is not satisfied: R#m precedes S#m.
- A prepends P, which is satisfied: P#m precedes A#m.
- A includes S, which is satisfied: A#m precedes S#m.

Note that all the dependencies can be satisfied at all:

  A.new.m #=> Q, P, A, S, R

-- 
Yusuke Endoh <mame / tsg.ne.jp>


-- 
http://bugs.ruby-lang.org/