Bug #17726: `respond_to_missing?` doesn't raise when called from `defined?`

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 3.1.0dev (2021-03-16T19:10:11Z master 58660e9434) [x86_64-darwin20]
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN

[tenderlovemaking (Aaron Patterson)]

I'm not sure whether or not this is expected behavior, but if respond_to_missing? is called from defined?, it won't raise an exception.

For example:

class Foo
  def respond_to_missing?(*args)
    puts "hi"
    raise
  end
end
foo = Foo.new
p defined?(foo.bar)

If you run this program, the output is this:

$ ruby -v test.rb
ruby 3.1.0dev (2021-03-16T19:10:11Z master 58660e9434) [x86_64-darwin20]
hi
nil

But I would expect this to raise an exception. Is the current behavior the desired behavior?

Thanks!

[jeremyevans0 (Jeremy Evans)]

I believe this is expected. defined? swallows exceptions in other cases, such as when a method raises an exception:

class Foo
  def bar(*args)
    puts "hi"
    raise
  end
end
foo = Foo.new
p defined?(foo.bar.to_s)

[jeremyevans0 (Jeremy Evans)]

• Status changed from Open to Closed