[ruby-core:96158] [Ruby master Bug#15758] Object.const_defined?(name) falsely returns true on classes that are not defined

Issue #15758 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 2.4: DONTNEED, 2.5: DONTNEED, 2.6: REQUIRED to 2.4: DONTNEED, 2.5: DONTNEED, 2.6: DONE

ruby_2_6 r67830 merged revision(s) e1b592b508c72a56ae012869d97fe1580ff87246,d10451f3fd51f577e704db770de48d05044eb45c.

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Bug #15758: Object.const_defined?(name) falsely returns true on classes that are not defined
https://bugs.ruby-lang.org/issues/15758#change-83036

* Author: dux (Dino Reic)
* Status: Closed
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.6.2, 2.7.0-dev
* Backport: 2.4: DONTNEED, 2.5: DONTNEED, 2.6: DONE
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in short https://i.imgur.com/qvIIBuu.png

Object.const_defined?('Baz::Bar') -> true

yet Baz::Bar -> class not found!

test to run, all ok on ruby 2.6.0, bug in 2.6.2

~~~ruby
class Foo
end

class Bar
end

class Baz
  class Foo
  end
end

###

def report klass
  name     = "Object.const_defined?('%s')" % klass
  exists   = Object.const_defined?(klass)
  instance = eval klass rescue nil
  check    = (exists && instance) || (!exists && !instance)? 'ok' : 'ERROR!'

  puts [
    name.ljust(35),
    exists.to_s.ljust(5),
    (instance ? instance.to_s : 'nil').ljust(8),
    check
  ].join(' -> ')
end

report 'Foo'
report 'Bar'
report 'Baz'
report 'Naat'
report 'Baz::Foo'
report 'Baz::Bar'
report 'Baz::Naat'
puts   '---'
report 'Baz::Foo::Bar::Baz::Foo' # true in 2.6.2 :)
~~~

running produces output

~~~
Object.const_defined?('Foo')        -> true  -> Foo      -> ok
Object.const_defined?('Bar')        -> true  -> Bar      -> ok
Object.const_defined?('Baz')        -> true  -> Baz      -> ok
Object.const_defined?('Naat')       -> false -> nil      -> ok
Object.const_defined?('Baz::Foo')   -> true  -> Baz::Foo -> ok
Object.const_defined?('Baz::Bar')   -> true  -> nil      -> ERROR!
Object.const_defined?('Baz::Naat')  -> false -> nil      -> ok
---
Object.const_defined?('Baz::Foo::Bar::Baz::Foo') -> true  -> nil      -> ERROR!
~~~


---Files--------------------------------
bug.rb (581 Bytes)


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