Bug #11493: IRB/Ruby completely exits when attempting to use NoMethodError exception in BasicObject

• Status: Rejected
• Assignee: aycabta (aycabta .)
• Target version: -
• ruby -v: 2.2.0
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN

[iMIchael (Michael Martinez)]

Summary

Was playing around with BasicObject to implement my own undefined method message and found this issue in IRB

$ ruby --version
ruby 2.2.0p0 (2014-12-25 revision 49005) [x86_64-darwin14]
$ irb
2.2.0 :002 > class BasicObject
2.2.0 :003?>   def method_missing(name, *args, &block)
2.2.0 :004?>     raise(NoMethodError, " '#{name}' is an undefined method, dude!")
2.2.0 :005?>     end
2.2.0 :006?>   end
 => :method_missing 
2.2.0 :008 > 234234.asdasdasd
NameError: uninitialized constant BasicObject::NoMethodError
(irb):4:in `method_missing': uninitialized constant BasicObject::NoMethodError (NameError)
	from /Users/home/.rvm/scripts/irbrc.rb:32:in `initialize'
	from /Users/home/.rvm/scripts/irbrc.rb:32:in `open'
	from /Users/home/.rvm/scripts/irbrc.rb:32:in `block in <top (required)>'
(irb):4:in `method_missing': uninitialized constant BasicObject::NoMethodError (NameError)
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/workspace.rb:106:in `sub'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/workspace.rb:106:in `filter_backtrace'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:511:in `block (3 levels) in eval_input'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:510:in `each'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:510:in `block (2 levels) in eval_input'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:623:in `signal_status'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:486:in `block in eval_input'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:245:in `block (2 levels) in each_top_level_statement'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:231:in `loop'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:231:in `block in each_top_level_statement'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:230:in `catch'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb/ruby-lex.rb:230:in `each_top_level_statement'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:485:in `eval_input'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:395:in `block in start'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:394:in `catch'
	from /Users/home/.rvm/rubies/ruby-2.2.0/lib/ruby/2.2.0/irb.rb:394:in `start'
	from /Users/home/.rvm/rubies/ruby-2.2.0/bin/irb:11:in `<main>'
$ echo $?
1

Expected Results

I expect IRB to handle Ruby errors without exiting completely. The same way "foo".asdfasdf() raises a NoMethodError, but doesn't actually completely die.

Actual Results

Fatal error resulting in the Ruby process exiting.

[jeremyevans0 (Jeremy Evans)]

This error still occurs in master. However, I'm not sure it is fixable with the example you gave. Your example does not raise NoMethodError, it raises NameError, because you used NoMethodError instead of ::NoMethodError. Even if you fix that, defining BasicObject#method_missing overrides the existing version, which breaks ton of internal code, not just irb. Even a simple thing like using backticks is broken if you do that (and irb ends up using backticks), because Ruby will attempt to call such a method_missing method (in rb_check_funcall_default) in many cases.

If you do want to wrap NoMethodErrors with a different exception message, you could try:

module BasicObjectMM
  def method_missing(name, *args, &block)
    super
  rescue => e
    e.message.replace("'#{name}' is an undefined method, dude!")
    ::Kernel.raise(e)
  end
end
BasicObject.prepend(BasicObjectMM)

[ko1 (Koichi Sasada)]

• Assignee set to aycabta (aycabta .)

[ko1 (Koichi Sasada)]

• Status changed from Open to Rejected

could you make an issue and continue to discuss on https://github.com/ruby/irb ?

Thanks,
Koichi