[ruby-core:83975] [Ruby trunk Feature#1586] Including a module already present in ancestors should not be ignored

Issue #1586 has been updated by marcandre (Marc-Andre Lafortune).


Thank you for the consideration.

May I add two observations?

1) `prepend` had similar behavior (ignoring already prepended modules) in 2.0 and 2.1. It was changed in 2.2 and I don't remember incompatibility problems.

2) If incompatibility is actually an issue, could we detect cases where we ignore wrongly an include and issue a warning, and make the changes in the next version?

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Feature #1586: Including a module already present in ancestors should not be ignored
https://bugs.ruby-lang.org/issues/1586#change-68055

* Author: bitsweat (Jeremy Daer)
* Status: Rejected
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: Next Major
----------------------------------------
=begin
 The scenario:
 * I include Foo in Numeric to provide #bar
 * Some other library includes a module in Float to provide #bar
 * So I include Foo in Float to use my #bar
 * But including Foo in Float is ignored since it's already in the ancestor chain
 
 I think it should be added to the ancestor chain, even if it's already present, since I may want to override some other method earlier in the ancestor chain.
 
 # Including a module already included in a superclass is ignored
 >> module Foo; end
 => nil
 >> class Numeric; include Foo; end
 => Numeric
 >> Float.ancestors
 => [Float, Precision, Numeric, Foo, Comparable, Object, Kernel]
 >> class Float; include Foo; end
 => Float
 >> Float.ancestors
 => [Float, Precision, Numeric, Foo, Comparable, Object, Kernel]
  
 # Reversing the order of inclusion works as expected
 >> module Foo; end
 => nil
 >> class Float; include Foo; end
 => Float
 >> Float.ancestors
 => [Float, Foo, Precision, Numeric, Comparable, Object, Kernel]
 >> class Numeric; include Foo; end
 => Numeric
 >> Float.ancestors
 => [Float, Foo, Precision, Numeric, Foo, Comparable, Object, Kernel]
  
 # And so does including a dupe of the existing module in the subclass
 >> module Foo; end
 => nil
 >> class Numeric; include Foo; end
 => Numeric
 >> Float.ancestors
 => [Float, Precision, Numeric, Foo, Comparable, Object, Kernel]
 >> class Float; include Foo.dup; end
 => Float
 >> Float.ancestors
 => [Float, #<Module:0x19bcd40>, Precision, Numeric, Foo, Comparable, Object, Kernel]
=end


---Files--------------------------------
inclusion.pdf (56.4 KB)


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