Bug #17509: Custom respond_to? methods in modules break defined?(super)

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-darwin19]
• Backport: 2.5: DONTNEED, 2.6: DONTNEED, 2.7: DONTNEED, 3.0: DONE

[benediktdeicke (Benedikt Deicke)]

When using defined?(super) to check that a superclass method exists before calling super, including modules with a custom respond_to? method seems to break the check so it wrongfully returns a truthy value, even though the superclass method doesn't exist.

This only happens on Ruby 3.0.0 and works fine on previous Ruby versions. This is possibly related to this change: https://github.com/ruby/ruby/pull/3777

Example

module SomeModule
  def a_method
    defined?(super) ? super : :no_super_method
  end
end

module RespondModule
  def respond_to?(*)
    super
  end
end

class PlainClass
  include SomeModule
end

class ModuleClass
  include RespondModule
  include SomeModule
end

puts "PlainClass: #{PlainClass.new.a_method}"
puts "ModuleClass: #{ModuleClass.new.a_method}"

Actual Result on Ruby 3.0.0p0

PlainClass: no_super_method
test.rb:3:in `a_method': super: no superclass method `a_method' for #<ModuleClass:0x00007fd77383f908> (NoMethodError)
Did you mean?  method
	from test.rb:24:in `<main>'

Expected Result (like on older versions)

PlainClass: no_super_method
ModuleClass: no_super_method

Thanks to Rafael França for helping me unravel this.

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

[nobu (Nobuyoshi Nakada)]

• Related to Bug #11213: defined?(super) ignores respond_to_missing? added

[nobu (Nobuyoshi Nakada)]

• Backport changed from 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN to 2.5: DONTNEED, 2.6: DONTNEED, 2.7: DONTNEED, 3.0: REQUIRED

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

Applied in changeset git|85b5d4c8bf4cdcba4f1af65f2bc0c8ac716cb795.

---

Revert "[Bug #11213] let defined?(super) call respond_to_missing?"

This reverts commit fac2498e0299f13dffe4f09a7dd7657fb49bf643 for
now, due to [Bug #17509], the breakage in the case super is
called in respond_to?.

[naruse (Yui NARUSE)]

• Backport changed from 2.5: DONTNEED, 2.6: DONTNEED, 2.7: DONTNEED, 3.0: REQUIRED to 2.5: DONTNEED, 2.6: DONTNEED, 2.7: DONTNEED, 3.0: DONE

ruby_3_0 147453ad1e85bc94506c269e363e736675946908 merged revision(s) 85b5d4c8bf4cdcba4f1af65f2bc0c8ac716cb795.