Feature #14944: Support optional inherit argument for Module#method_defined?

• Status: Closed
• Assignee: -
• Target version: -

[jeremyevans0 (Jeremy Evans)]

Module has many introspection methods for methods and constants that
either return an array or return true or false for whether the method
or constant is defined. Most of these methods support an optional
argument that controls whether to consider inheritance. Currently,
the following Module methods support such a argument:

• const_defined?
• constants
• instance_methods
• private_instance_methods
• protected_instance_methods
• public_instance_methods

and the following methods do not:

• method_defined?
• private_method_defined?
• protected_method_defined?
• public_method_defined?

This patch supports such an argument for the *method_defined?
methods.

While you can currently work around the lack of support via:

mod.instance_methods(false).include?(:method_name)

This patch allows the simpler and more efficient:

mod.method_defined?(:method_name, false)

One case where you want to exclude inheritance when checking
for a method definition is when you want to replace a method
that may already exist. To avoid a verbose warning, you want
to remove the method only if it is already defined:

remove_method(:foo) if method_defined?(:foo, false)
define_method(:foo){}

You can't call remove_method without checking for the method
definition, as that can raise a NameError, and you don't want
to include inheritance because remove_method will still raise
a NameError if the method is defined by an ancestor and not
by the module itself.

[znz (Kazuhiro NISHIYAMA)]

If you want to suppress warnings, you can use undef_method instead of remove_method for the time being.

module M
  def foo; end
end
class C
  include M
  undef_method(:foo) if method_defined?(:foo)
  define_method(:foo){}
end

[matz (Yukihiro Matsumoto)]

I think this is a good idea. Accepted.

Matz.

[usa (Usaku NAKAMURA)]

• Status changed from Open to Closed

Applied in changeset trunk|r64337.

---

Support optional inherit argument for Module#method_defined?

Module has many introspection methods for methods and constants that
either return an array or return true or false for whether the method
or constant is defined. Most of these methods support an optional
argument that controls whether to consider inheritance. Currently,
the following Module methods support such a argument:

• const_defined?
• constants
• instance_methods
• private_instance_methods
• protected_instance_methods
• public_instance_methods

and the following methods do not:

• method_defined?
• private_method_defined?
• protected_method_defined?
• public_method_defined?

This patch supports such an argument for the *method_defined?
methods.

While you can currently work around the lack of support via:

mod.instance_methods(false).include?(:method_name)

This patch allows the simpler and more efficient:

mod.method_defined?(:method_name, false)

One case where you want to exclude inheritance when checking
for a method definition is when you want to replace a method
that may already exist. To avoid a verbose warning, you want
to remove the method only if it is already defined:

remove_method(:foo) if method_defined?(:foo, false)
define_method(:foo){}

You can't call remove_method without checking for the method
definition, as that can raise a NameError, and you don't want
to include inheritance because remove_method will still raise
a NameError if the method is defined by an ancestor and not
by the module itself.

[ruby-core:88140] [Feature #14944]

From: Jeremy Evans [e-mail]

[nobu (Nobuyoshi Nakada)]

• Related to Bug #15597: syscall not returning true from private_method_defined? added

[sawa (Tsuyoshi Sawada)]

Actually, this proposal is a duplicate of #10797

[Eregon (Benoit Daloze)]

• Has duplicate Feature #10797: `inherit` parameter for `..._defined?` methods in Module added

[jeremyevans0 (Jeremy Evans)]

• Is duplicate of Feature #9322: method_defined? family of of methods should support the exclusion of ancestors added