Feature #6539: public and private for core methods

• Status: Closed
• Assignee: nobu (Nobuyoshi Nakada)
• Target version: -

[marcandre (Marc-Andre Lafortune)]

I feel there are inconsistencies in which methods are public and which are private.

For example:

  obj = []
  prev = obj.instance_variable_get(:@foo) # allowed
  obj.instance_variable_set(:@foo, nil)    # allowed
  # But these are almost equivalent to:
  prev = obj.remove_instance_variable(:@foo)
    # => NoMethodError: private method `remove_instance_variable' called for []:Array

Another example:

  module M
    def foo
      42
    end
  end

  M.module_function :foo # private method `module_function' called for M:Module
  M.extend M             # allowed
  M.foo # => 42

Reverse example:

  {}.method_missing :foo    # => private method `method_missing' called
  {}.respond_to_missing? :foo, false   # => allowed, why?

Which methods should be private is a different question for Ruby than for apps and libraries; the "real" private methods of Ruby are in C!
For Ruby, I feel that a method should be private if it is not meant to be called except by Ruby itself (callbacks, etc...), or if it's a "global" methods of Kernel that is meant to be called directly (i.e. puts instead of 42.puts)

Otherwise, it should be public. This includes methods like Module#include.

I don't know what the rationale was to make include and the like private.

I feel it is now quite common to use metaprogramming, e.g. to include modules from outside a class. It's part of a Class' API that it can be extended and modified, so these methods should be public.

Concrete proposal:

Should be made private:

  Object and descendants
    #initialize_clone
    #initialize_dup
    #respond_to_missing?
  Rational & Complex
    #marshal_dump
    #marshal_load
  Time
    #_dump
    ._load

Note that Delegate#initialize_{clone|dup} are already private

Should be made public:

  Object
    #remove_instance_variable
  Module
    #attr
    #attr_reader
    #attr_writer
    #attr_accessor
    #remove_const
    #include
    #remove_method
    #undef_method
    #alias_method
    #public
    #protected
    #private
    #module_function
    #define_method

[marcandre (Marc-Andre Lafortune)]

• Assignee set to matz (Yukihiro Matsumoto)

No comments, so I'm assigning to Matz.

There are more than 150 older issues assigned to Matz already.

[mame (Yusuke Endoh)]

• Status changed from Open to Assigned

[matz (Yukihiro Matsumoto)]

• Assignee changed from matz (Yukihiro Matsumoto) to nobu (Nobuyoshi Nakada)

Concrete counter proposal:

Should be made private:
Object and descendants
#initialize_clone
#initialize_dup
#respond_to_missing?
Rational & Complex
#marshal_dump
#marshal_load
Time
#_dump
._load

Note that Delegate#initialize_{clone|dup} are already private

Should be made public:

Object
#remove_instance_variable

I think class/module operations should be done in the scope.

Matz.

[mame (Yusuke Endoh)]

• Target version changed from 2.0.0 to 2.6

[nobu (Nobuyoshi Nakada)]

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

This issue was solved with changeset r38113.
Marc-Andre, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.

---

vm_method.c: make initialize methods private

• id.c (Init_id), template/id.h.tmpl: add initialize_{copy,clone,dup}
  and respond_to_missing?.
• vm_method.c (rb_method_entry_make): make above methods private.
  [Feature #6539]

[ko1 (Koichi Sasada)]

• Description updated (diff)

[shyouhei (Shyouhei Urabe)]

• Related to Feature #12697: Why shouldn't Module meta programming methods be public? added

[marcandre (Marc-Andre Lafortune)]

• Related to Feature #14132: Module#attr{|_reader|_writer} should be public added

[marcandre (Marc-Andre Lafortune)]

• Related to Feature #14133: Module#{define|alias|undef}_method should be made public added