Ruby

Bug #11326

Updated by nobu (Nobuyoshi Nakada) almost 10 years ago

Hi, 

 yesterday I've stumbled on weird behavior defining writers as Struct members. 

 While this code works on MRI it breaks on JRuby and Rubinius: 

 ```ruby 
 Struct.new(:x=).new(nil).x = 23 
 ``` 

 On JRuby it fails with: 

 ``` 
 ArgumentError: wrong number of arguments calling `x=` (1 for 0) 
     from (irb):1:in `evaluate' 
     from org/jruby/RubyKernel.java:1111:in `eval' 
     from org/jruby/RubyKernel.java:1511:in `loop' 
     from org/jruby/RubyKernel.java:1274:in `catch' 
     from org/jruby/RubyKernel.java:1274:in `catch' 
     from /home/ps/.rvm/rubies/jruby-1.7.20/bin/irb:13:in `(root)' 
 ```  

 On Rubinius it gives: 

 ``` 
 ArgumentError: given 1, expected 0 
     from (irb):1 
     from kernel/common/block_environment.rb:53:in `call_on_instance' 
     from kernel/common/eval.rb:176:in `eval' 
     from kernel/common/kernel.rb:510:in `loop' 
     from kernel/bootstrap/proc.rb:20:in `call' 
     from kernel/common/throw_catch.rb:30:in `catch' 
     from kernel/common/throw_catch.rb:8:in `register' 
     from kernel/common/throw_catch.rb:29:in `catch' 
     from kernel/bootstrap/proc.rb:20:in `call' 
     from kernel/common/throw_catch.rb:30:in `catch' 
     from kernel/common/throw_catch.rb:8:in `register' 
     from kernel/common/throw_catch.rb:29:in `catch' 
     from /home/ps/.rvm/gems/rbx-2.5.2@global/gems/rubysl-irb-2.1.1/bin/irb:12:in `__script__' 
     from kernel/common/kernel.rb:497:in `load' 
     from /home/ps/.rvm/gems/rbx-2.5.2@global/bin/irb:23:in `__script__' 
     from kernel/delta/code_loader.rb:66:in `load_script' 
     from kernel/delta/code_loader.rb:152:in `load_script' 
     from kernel/loader.rb:655:in `script' 
     from kernel/loader.rb:809:in `main' 
 ``` 

 I've reported this as a bug to the JRuby team at https://github.com/jruby/jruby/issues/3097 

 Charles rejected it and said: 

 > ``` 
 I think I'm going to call this a bug in MRI and ask you to re-file it with them. I believe the `:x=` :x= should be kicked out as an invalid attribute name rather than defined as a write-only attribute. I believe the latter behavior is happening only accidentally because of how MRI detects that you're defining an `=` = method. 
 ``` 

 So here I am. 

 I don't have a strong opinion whether defining a writer member should be possible or not. 

 It would be nice to have one single behavior across the 3 major Ruby implementations :) 

 What do you think? 

 Kind regards, 
   Peter

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