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Feature #16123

Allow calling a private method with `self.`

Added by dylants (Dylan Thacker-Smith) 23 days ago. Updated 23 days ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:94511]

Description

Problem

There is an inconsistency between calling a private attribute writer being allowed with self.value = syntax and self.value not being allowed on a private attribute writer.

Calling a private method in this way can be useful when trying to assign the return value of this private method to a local variable with the same name.

Solution

The attached patch handles this by compiling the calling into a function call by using the VM_CALL_FCALL flag, so it is as if the call were made without the self. prefix, except it won't be confused with local variables at the VM instruction level. It is also compiled like an assignment call, except I didn't use the COMPILE_RECV macro, since that would remove the CHECK macro usage around the COMPILE line.


Files

0001-Allow-calling-a-private-method-with-self.diff.txt (3.28 KB) 0001-Allow-calling-a-private-method-with-self.diff.txt Allow calling a private method with `self.` dylants (Dylan Thacker-Smith), 08/23/2019 08:44 PM

History

Updated by shevegen (Robert A. Heiler) 23 days ago

I may not completely understand the issue description. What is the inconsistency? (That is a honest
question, by the way; I am not fully understanding the issue domain.)

I am not even entirely sure what a private attribute writer is either; can we use these terms when
we can use e. g. send() at all times? I may not understand this, but I assume you can get the value
of any method via .send() and assign it to the local variable?

Updated by dylants (Dylan Thacker-Smith) 23 days ago

Here is a script to help demonstrate the inconsistency, where self.bar = 123 is allowed by self.bar is not.

class Foo
  def foo
    self.bar = 123 # allowed
    self.bar # raises
  end

  private

  attr_accessor :bar
end

Foo.new.foo

By attribute writer, I was just referring to an assignment method like the one defined by attr_writer, although the same applies to any assignment method like def bar=(value); value; end. The inconsistency is just more obvious when dealing with the pair of methods defined by attr_accessor if they are private because self. works with one of them but not the other as shown above.

shevegen (Robert A. Heiler) wrote:

I may not understand this, but I assume you can get the value of any method via .send() and assign it to the local variable?

Yes, it can be easily worked around, it just doesn't seem like it should be necessary to workaround this limitation. The point of private is to keep things from being accessible from other objects, which we know isn't the case when a call is made on self. directly.

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