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Prepending a module to a module extended by a class gives NPE when calling super #4678

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donv opened this issue Jun 19, 2017 · 5 comments
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Prepending a module to a module extended by a class gives NPE when calling super #4678

donv opened this issue Jun 19, 2017 · 5 comments
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JRuby 9.3.0.0

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@donv
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donv commented Jun 19, 2017

jruby 9.1.12.0 (2.3.3) 2017-06-15 33c6439 Java HotSpot(TM) 64-Bit Server VM 25.112-b16 on 1.8.0_112-b16 +jit [darwin-x86_64]
Darwin Gratass.local 16.6.0 Darwin Kernel Version 16.6.0: Fri Apr 14 16:21:16 PDT 2017; root:xnu-3789.60.24~6/RELEASE_X86_64 x86_64

Given the following code:

module A
  def self.included(clazz)
    clazz.extend ClassMethods
  end

  module ClassMethods
    def foo
      puts 'super'
    end
  end
end

class B
  include A
end

module C
  def foo
    super
  end
end
A::ClassMethods.prepend C

B.foo

JRuby 9.1.12.0 gives the following stack trace:

Unhandled Java exception: java.lang.NullPointerException
java.lang.NullPointerException: null
                      unresolvedSuper at org/jruby/ir/runtime/IRRuntimeHelpers.java:1014
  invokeSuper6:-unknown-super-target- at jruby_example.rb:19
                                  foo at jruby_example.rb:19
                                 call at org/jruby/internal/runtime/methods/CompiledIRMethod.java:155
                         cacheAndCall at org/jruby/runtime/callsite/CachingCallSite.java:318
                                 call at org/jruby/runtime/callsite/CachingCallSite.java:131
                    invokeOther10:foo at jruby_example.rb:24
                               <main> at jruby_example.rb:24
                  invokeWithArguments at java/lang/invoke/MethodHandle.java:627
                                 load at org/jruby/ir/Compiler.java:95
                            runScript at org/jruby/Ruby.java:827
                          runNormally at org/jruby/Ruby.java:746
                          runNormally at org/jruby/Ruby.java:764
                          runFromMain at org/jruby/Ruby.java:577
                        doRunFromMain at org/jruby/Main.java:417
                          internalRun at org/jruby/Main.java:305
                                  run at org/jruby/Main.java:232
                                 main at org/jruby/Main.java:204

With MRI 2.4.1 it prints "super".
@donv donv changed the title Prepending a module to a module extended by a class gives NPE Prepending a module to a module extended by a class gives NPE when calling super Jun 19, 2017
@donv
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donv commented Jun 19, 2017

Workaround is to postpone the include call to after the prependcall.

Possible duplicate of #4531.

@deivid-rodriguez deivid-rodriguez mentioned this issue Oct 17, 2018
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@headius headius mentioned this issue Jan 31, 2019
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@headius
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headius commented Mar 13, 2019

This no longer NPEs but still fails:

$ jruby blah.rb
NoMethodError: super: no superclass method `foo' for B:Class
Did you mean?  fork
  method_missing at org/jruby/RubyBasicObject.java:1708
             foo at blah.rb:19
          <main> at blah.rb:24

@headius headius added this to the JRuby 9.2.8.0 milestone Apr 9, 2019
@headius headius removed this from the JRuby 9.2.8.0 milestone Aug 1, 2019
@headius headius mentioned this issue Oct 29, 2019
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@headius headius added this to the JRuby 9.2.10.0 milestone Oct 29, 2019
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headius commented Feb 16, 2020

Slightly simpler example:

module X
  def foo
    puts "super"
  end
end

class B
  class << self
    include X
  end
end

module C
  def foo
    super
  end
end

X.prepend C

B.foo

@headius headius modified the milestones: JRuby 9.2.10.0, JRuby 9.3.0.0 Feb 18, 2020
@olleolleolle olleolleolle mentioned this issue Mar 26, 2020
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headius commented Mar 26, 2020

doudou/flexmock#16 is another case of this; FlexMock prepends a proxy module onto the target class, which in that case is a class's class.

@ahorek ahorek mentioned this issue Jul 29, 2020
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@enebo
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enebo commented Aug 20, 2021

Fixed in PR #6777

@enebo enebo closed this as completed Aug 20, 2021
@headius headius mentioned this issue Sep 22, 2021
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