Bug #10985: Ruby 2.2 respond_to_missing?/method_missing/Object#method is not detecting properly

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: 2.2.1p85
• Backport: 2.0.0: DONTNEED, 2.1: DONTNEED, 2.2: DONE

[michaelherold (Michael Herold)]

I'm one of the maintainers of the hashie gem. We had some reports that one of our specs started failing with Ruby 2.2 (and it was failing in ruby-head before then, but no one noticed), where Object#method was not picking up a respond_to_missing?/method_missing combo for our dynamic setters. This only occurs when we are dynamically constructing the method name from a string.

I have isolated the issue out into a tiny sample project that shows the issue. You can see that sample on Github. That repository is set up to have Travis run on Ruby 2.1.5, 2.2.0, 2.2.1, and ruby-head to show that the issue is introduced in the 2.2 line.

I'm having trouble isolating the issue down at the C level, but from a Ruby level, it seems that dynamically constructed symbols aren't the same as explicitly constructed (i.e. fully typed out) symbols. Using the syntax from my little test repository:

widget = Widget.new

widget.method(:abc=)  #=> This is found
widget.method("abc=") #=> This is found because it has previously been accessed via a symbol

widget.method("xyz=") #=> This is NOT found
widget.method(:xyz=)  #=> This is found
widget.method("xyz=") #=> Now this is found because it was previously accessed via a symbol

Because of that behavior, it makes me think that something is happening with the conversion of the argument to a symbol, but that could be way off.

Please let me know if the explanation is vague. I'm happy to provide any more information that you would find helpful.

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r50038.

---

proc.c: respond_to_missing? at Method

• proc.c (respond_to_missing_p): check if the receiver responds to
  the given method by respond_to_missing?.
• proc.c (mnew_missing): create Method object for method_missing.
  [ruby-core:68564] [Bug #10985]

[nobu (Nobuyoshi Nakada)]

• Status changed from Closed to Open
• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN to 2.0.0: DONTNEED, 2.1: DONTNEED, 2.2: REQUIRED

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

[michaelherold (Michael Herold)]

Thank you for the fix and the swift turnaround, Nakada-san! I'm looking forward to the backport.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: DONTNEED, 2.1: DONTNEED, 2.2: REQUIRED to 2.0.0: DONTNEED, 2.1: DONTNEED, 2.2: DONE

Backported into ruby_2_2 branch at r50546.