bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Xu Chunyang]

(info "(eieio) Predicates") mentions

 -- Function: eieio-class-name class
     Return a string of the form ‘#<class myclassname>’ which should
     look similar to other Lisp objects like buffers and processes.
     Printing a class results only in a symbol.

but it is not right, the value is not string at all, it's a symbol

  (defclass my-class () ())
  ;; => my-class

  (eieio-class-name 'my-class)
  ;; => my-class

  (type-of (eieio-class-name 'my-class))
  ;; => symbol

The git master produced the same result as Emacs 26.3. I notice Emacs
24.3's class-name produces the expected result and the function is
replaced by eieio-class-name since 24.4

   (define-obsolete-function-alias 'class-name #'eieio-class-name "24.4")

however, these two functions are different. It seems eieio-class-name
contains a bug, the name suggests its value is a string, but it
returns a symbol.

bug#38374: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Xu Chunyang]

I sent this report two days ago, but it seems it is not received
because debbugs.gnu.org was down.

---------- Forwarded message ---------
From: Xu Chunyang <xuchunyang56@gmail.com>
Date: Sun, Nov 24, 2019 at 11:11 PM
Subject: 26.3; The info doc of eieio-class-name is outdated and its
value looks incorrect
To: <bug-gnu-emacs@gnu.org>


(info "(eieio) Predicates") mentions

 -- Function: eieio-class-name class
     Return a string of the form ‘#<class myclassname>’ which should
     look similar to other Lisp objects like buffers and processes.
     Printing a class results only in a symbol.

but it is not right, the value is not string at all, it's a symbol

  (defclass my-class () ())
  ;; => my-class

  (eieio-class-name 'my-class)
  ;; => my-class

  (type-of (eieio-class-name 'my-class))
  ;; => symbol

The git master produced the same result as Emacs 26.3. I notice Emacs
24.3's class-name produces the expected result and the function is
replaced by eieio-class-name since 24.4

   (define-obsolete-function-alias 'class-name #'eieio-class-name "24.4")

however, these two functions are different. It seems eieio-class-name
contains a bug, the name suggests its value is a string, but it
returns a symbol.

bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Lars Ingebrigtsen]

Xu Chunyang <xuchunyang56@gmail.com> writes:

> (info "(eieio) Predicates") mentions
>
>  -- Function: eieio-class-name class
>      Return a string of the form ‘#<class myclassname>’ which should
>      look similar to other Lisp objects like buffers and processes.
>      Printing a class results only in a symbol.
>
> but it is not right, the value is not string at all, it's a symbol
>
>   (defclass my-class () ())
>   ;; => my-class
>
>   (eieio-class-name 'my-class)
>   ;; => my-class
>
>   (type-of (eieio-class-name 'my-class))
>   ;; => symbol
>
> The git master produced the same result as Emacs 26.3. I notice Emacs
> 24.3's class-name produces the expected result and the function is
> replaced by eieio-class-name since 24.4
>
>    (define-obsolete-function-alias 'class-name #'eieio-class-name "24.4")
>
> however, these two functions are different. It seems eieio-class-name
> contains a bug, the name suggests its value is a string, but it
> returns a symbol.

My guess is that the documentation in the manual just wasn't updated
when this stuff was rewritten back in 2014, and that the return value is
correct.  Stefan?

Currently we have

(defun eieio--class-print-name (class)
  "Return a printed representation of CLASS."
  (format "#<class %s>" (eieio-class-name class)))

(defun eieio-class-name (class)
  "Return a Lisp like symbol name for CLASS."
  (setq class (eieio--class-object class))
  (cl-check-type class eieio--class)
  (eieio--class-name class))
(define-obsolete-function-alias 'class-name #'eieio-class-name "24.4")

but eieio--class-print-name is only used as a fallback in one of the
prin1 cases.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Stefan Monnier]

>> however, these two functions are different. It seems eieio-class-name
>> contains a bug, the name suggests its value is a string, but it
>> returns a symbol.

FWIW, here a class's name is indeed a symbol: the "not a name" version
would be the class object itself (a struct).


        Stefan

bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Lars Ingebrigtsen]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>>> however, these two functions are different. It seems eieio-class-name
>>> contains a bug, the name suggests its value is a string, but it
>>> returns a symbol.
>
> FWIW, here a class's name is indeed a symbol: the "not a name" version
> would be the class object itself (a struct).

I've now updated the manual to say what it really returns now, but it's
not a very useful function.  :-)  (I mean, it just returns its argument.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Stefan Monnier]

> I've now updated the manual to say what it really returns now, but it's
> not a very useful function.  :-)  (I mean, it just returns its argument.)

It returns its argument only if its argument was a class name.
It's more useful when its argument is a class object (or when you don't
know which of the two it will be).


        Stefan

bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Lars Ingebrigtsen]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> I've now updated the manual to say what it really returns now, but it's
>> not a very useful function.  :-)  (I mean, it just returns its argument.)
>
> It returns its argument only if its argument was a class name.
> It's more useful when its argument is a class object (or when you don't
> know which of the two it will be).

(eieio-class-name (make-instance 'my-class))
=>
Debugger entered--Lisp error: (wrong-type-argument eieio--class #<my-class my-class-158f4e54cbbc> class)
  signal(wrong-type-argument (eieio--class #<my-class my-class-158f4e54cbbc> class))
  eieio-class-name(#<my-class my-class-158f4e54cbbc>)
  eval((eieio-class-name (make-instance 'my-class)) t)

On the other hand:

(eieio-object-class-name (make-instance 'my-class))
=> my-class

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

bug#38365: 26.3; The info doc of eieio-class-name is outdated and its value looks incorrect

[Lars Ingebrigtsen]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> It returns its argument only if its argument was a class name.
> It's more useful when its argument is a class object (or when you don't
> know which of the two it will be).

Oh, class object, not object.  Never mind.  :-)

(eieio-class-name (eieio--class-object 'my-class))
=> my-class

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no