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Crash involving the use of DelegateClass in Ruby 2.7 #1273

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backus opened this issue Nov 7, 2021 · 7 comments
Closed

Crash involving the use of DelegateClass in Ruby 2.7 #1273

backus opened this issue Nov 7, 2021 · 7 comments
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@backus
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backus commented Nov 7, 2021 •
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I'm working on upgrading an app to Ruby 2.7 from Ruby 2.6.8 and ran into a crash that only happens under 2.7.

Consider the following code:

require 'delegate'

module MutantCrash
  class Foo
  end

  class Thing < DelegateClass(Foo)
    def bar; end
  end
end

Running under 2.6 works fine:

$ ruby -v
ruby 2.6.6p146 (2020-03-31 revision 67876) [x86_64-darwin19]

$ cat Gemfile.lock | grep mutant
  remote: https://com:xxx@gem.mutant.dev/
    mutant (0.10.35)
    mutant-license (0.1.1.1.3319570810364303218730943090542303819067.3)
    mutant-rspec (0.10.35)
      mutant (= 0.10.35)
  mutant (~> 0.10.35)
  mutant-license!
  mutant-rspec (~> 0.10.35)

$ bundle exec mutant run --include lib --require example --use rspec 'MutantCrash*' > /dev/null
warning: parser/current is loading parser/ruby26, which recognizes
warning: 2.6.8-compliant syntax, but you are running 2.6.6.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
Uncovered mutations detected, exiting nonzero!

2.7 produces a crash

$ ruby -v
ruby 2.7.4p191 (2021-07-07 revision a21a3b7d23) [x86_64-darwin20]

$ cat Gemfile.lock | grep mutant
  remote: https://com:xxx@gem.mutant.dev/
    mutant (0.10.35)
    mutant-license (0.1.1.1.3319570810364303218730943090542303819067.3)
    mutant-rspec (0.10.35)
      mutant (= 0.10.35)
  mutant (~> 0.10.35)
  mutant-license!
  mutant-rspec (~> 0.10.35)

$ bundle exec mutant run --include lib --require example --use rspec 'MutantCrash*' > /dev/null
Traceback (most recent call last):
	45: from /dev/gems/ruby-2.7.4/bin/ruby_executable_hooks:22:in `<main>'
	44: from /dev/gems/ruby-2.7.4/bin/ruby_executable_hooks:22:in `eval'
	43: from /dev/gems/ruby-2.7.4/bin/mutant:23:in `<main>'
	42: from /dev/gems/ruby-2.7.4/bin/mutant:23:in `load'
	41: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/bin/mutant:47:in `<top (required)>'
	40: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/cli/command.rb:55:in `call'
	39: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/cli/command.rb:81:in `execute'
	38: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/cli/command/environment/run.rb:44:in `action'
	37: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/either.rb:115:in `bind'
	36: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/cli/command/environment/run.rb:44:in `block in action'
	35: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/cli/command/environment.rb:28:in `bootstrap'
	34: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/either.rb:115:in `bind'
	33: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/cli/command/environment.rb:28:in `block in bootstrap'
	32: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/bootstrap.rb:38:in `call'
	31: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/filter.rb:16:in `call'
	30: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `call'
	29: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `flat_map'
	28: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `each'
	27: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:16:in `block in call'
	26: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/namespace.rb:17:in `call'
	25: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `call'
	24: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `flat_map'
	23: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `each'
	22: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:16:in `block in call'
	21: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/scope.rb:28:in `call'
	20: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `call'
	19: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `flat_map'
	18: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:15:in `each'
	17: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/chain.rb:16:in `block in call'
	16: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/methods.rb:24:in `call'
	15: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium/method_builder.rb:90:in `block (2 levels) in create_memoized_method'
	14: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium.rb:59:in `fetch'
	13: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium.rb:59:in `fetch'
	12: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium.rb:60:in `block in fetch'
	11: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium.rb:60:in `synchronize'
	10: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium.rb:61:in `block (2 levels) in fetch'
	 9: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium.rb:61:in `fetch'
	 8: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium.rb:62:in `block (3 levels) in fetch'
	 7: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium/method_builder.rb:91:in `block (3 levels) in create_memoized_method'
	 6: from /dev/gems/ruby-2.7.4/gems/unparser-0.6.0/lib/unparser/adamantium/method_builder.rb:91:in `call'
	 5: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/methods.rb:35:in `methods'
	 4: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/methods.rb:35:in `each_with_object'
	 3: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/methods.rb:35:in `each'
	 2: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/methods.rb:36:in `block in methods'
	 1: from /dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/methods.rb:90:in `access'
/dev/gems/ruby-2.7.4/gems/mutant-0.10.35/lib/mutant/matcher/methods.rb:90:in `instance_method': undefined method `!~' for class `MutantCrash::Thing' (NameError)
Did you mean?  !

I believe this is caused by a regression / bug in Ruby 2.7 (or maybe they intentionally did this? No clue). I noticed that the result of {public,protected,private}_instance_methods returns more values in 2.7 than it does in 2.6:

$ ruby -v
ruby 2.6.8p205 (2021-07-07 revision 67951) [x86_64-darwin20]

$ ruby -I lib -r example -e 'puts MutantCrash::Thing.public_instance_methods.size'
59

$ rvm use 2.7.4
$ ruby -I lib -r example -e 'puts MutantCrash::Thing.public_instance_methods.size'
64

Not sure if ruby core just changed DelegateClass a lot in 2.7, but this issue from @pocke 1 year ago seems related: https://bugs.ruby-lang.org/issues/16982
@mbj
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mbj commented Nov 7, 2021

Having an interesting time reproducing this within mutants test suite. Outside its fine. Still on it.

@mbj
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mbj commented Nov 7, 2021

reproduced within nice.

@mbj
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mbj commented Nov 7, 2021 •
edited
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@backus This is a bug in 2.7. 2.6 had an imperfect delegate, 2.7 a buggy and 3.0 fixed the issue.

require 'delegate'

puts("Ruby-Version: #{RUBY_VERSION}")

class Foo < DelegateClass(String)
  def foo
  end
end

if Foo.public_instance_methods.any? { |name| name.equal?(:!~) }
  puts ":!~ does exist!"
  p Foo.instance_method(:!~) # crashes only in 2.7
else
  puts ":!~ does NOT exist!"
end

@mbj
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mbj commented Nov 7, 2021 

Ruby-Version: 3.0.2
:!~ does exist!
#<UnboundMethod: String(Kernel)#!~(_)>
Ruby-Version: 2.6.6
:!~ does NOT exist!
Ruby-Version: 2.7.4
:!~ does exist!
Traceback (most recent call last):
	1: from x.rb:12:in `<main>'
x.rb:12:in `instance_method': undefined method `!~' for class `Foo' (NameError)
Did you mean?  !

@mbj mbj added the bug label Nov 7, 2021
@mbj mbj self-assigned this Nov 7, 2021
mbj added a commit that referenced this issue Nov 7, 2021
@mbj
Fix method matching on degenerate objects
e828cee 
[Fix #1273]
@mbj
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mbj commented Nov 7, 2021

@backus Can you check out #1275 (might be merged once you see this). It should make mutant skip over degenerate object interfaces like this case.

@mbj mbj closed this as completed in b642990 Nov 7, 2021
@backus
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backus commented Nov 7, 2021

@mbj just tried it out and it seems to work perfectly! Once you cut 0.11.1 I will upgrade our app accordingly. Thanks for getting to this so fast! Helped unblock our upgrade process 😃

@mbj
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mbj commented Nov 8, 2021

@backus 0.11.1 was released last night.

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