bug#18494: 24.4.50; defclass creates undocumented *-list-p function

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Tom Tromey]

Try:

(defclass zzz-whatever () ((hi)))

Now notice there is a new function:

(symbol-function 'zzz-whatever-list-p)
(lambda (obj) "Test OBJ to see if it a list of objects which are a child of type zzz-whatever" (when (listp obj) (let ((ans t)) (while (and obj ans) (setq ans (and (eieio-object-p (car obj)) (object-of-class-p (car obj) zzz-whatever))) (setq obj (cdr obj))) ans)))


This new -list-p function is not documented in the EIEIO manual.

It seems to me that it would be a bit better not to define it.
It doesn't seem generally useful enough, to me.

However, if it is kept, it ought to be documented.




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 of 2014-09-15 on bapiya
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Tom

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[David Engster]

[add CC Eric]

Tom Tromey writes:
> Try:
>
> (defclass zzz-whatever () ((hi)))
>
> Now notice there is a new function:
>
> (symbol-function 'zzz-whatever-list-p)
> (lambda (obj) "Test OBJ to see if it a list of objects which are a child of type zzz-whatever" (when (listp obj) (let ((ans t)) (while (and obj ans) (setq ans (and (eieio-object-p (car obj)) (object-of-class-p (car obj) zzz-whatever))) (setq obj (cdr obj))) ans)))
>
>
> This new -list-p function is not documented in the EIEIO manual.
>
> It seems to me that it would be a bit better not to define it.
> It doesn't seem generally useful enough, to me.

I agree it's not generally useful. It was added as a helper function to
validate a slot which should hold a list of objects (as part of the
EIEIO/EDE security fix for Emacs 23.4).

At least that's what I remember. I was under the impression that
eieio-persistent-validate/fix-slot-value would use this, but I cannot
see it; maybe it's just hidden very well. If it is not used, I'd agree
that it should better be removed or at least renamed to X--list-p.

Eric, WDYT?

-David

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Eric Ludlam]

  On 09/20/2014 06:41 AM, David Engster wrote:
> [add CC Eric]
>
> Tom Tromey writes:
>> Try:
>>
>> (defclass zzz-whatever () ((hi)))
>>
>> Now notice there is a new function:
>>
>> (symbol-function 'zzz-whatever-list-p)
>> (lambda (obj) "Test OBJ to see if it a list of objects which are a child of type zzz-whatever" (when (listp obj) (let ((ans t)) (while (and obj ans) (setq ans (and (eieio-object-p (car obj)) (object-of-class-p (car obj) zzz-whatever))) (setq obj (cdr obj))) ans)))
>>
>>
>> This new -list-p function is not documented in the EIEIO manual.
>>
>> It seems to me that it would be a bit better not to define it.
>> It doesn't seem generally useful enough, to me.
> I agree it's not generally useful. It was added as a helper function to
> validate a slot which should hold a list of objects (as part of the
> EIEIO/EDE security fix for Emacs 23.4).
>
> At least that's what I remember. I was under the impression that
> eieio-persistent-validate/fix-slot-value would use this, but I cannot
> see it; maybe it's just hidden very well. If it is not used, I'd agree
> that it should better be removed or at least renamed to X--list-p.

Hi,

I found that many of my programs that use EIEIO have slots that are of 
:type that is an object of some class, which is why there are base 
predicates.  Thus, if I have some object class foo, I can set to the 
:type of some other class to foo, instead of some other more complex 
type.  Having another predicate that also handles the list of objects 
that include subclasses is just handy.

David is right about the time when it was introduced, where only slots 
with a constrained :type for an object were allowed to be loaded in, 
allowing the loader to never 'eval anything, only read.

Technically, I could hand write a few of those predicates for the EDE 
loader, but I thought it would be generally useful, especially if other 
folk want to save their objects.  I'm not sure how widely used it is 
outside of EDE, semanticdb, and cogre which all have save files.  I 
certainly think it should be documented if consensus is that it stays.  
Perhaps an extra option for the defclass to add extra predicates along 
with :method-invocation-order.

Eric

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Stefan Monnier]

> Technically, I could hand write a few of those predicates for the EDE
> loader, but I thought it would be generally useful, especially if other folk
> want to save their objects.  I'm not sure how widely used it is outside of
> EDE, semanticdb, and cogre which all have save files.  I certainly think it
> should be documented if consensus is that it stays.  Perhaps an extra option
> for the defclass to add extra predicates along
> with :method-invocation-order.

My natural reaction is to say that those *-list-p predicates shouldn't
be automatically created, but could someone explain to me in detail
how/where they're used?
E.g. I hear it's used for types, but can't we use a type like (list foo)
instead of foo-list (or maybe (cl-every foo-p) instead of foo-list-p)?


        Stefan

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Eric Ludlam]

  On 09/20/2014 07:08 PM, Stefan Monnier wrote:
>> Technically, I could hand write a few of those predicates for the EDE
>> loader, but I thought it would be generally useful, especially if other folk
>> want to save their objects.  I'm not sure how widely used it is outside of
>> EDE, semanticdb, and cogre which all have save files.  I certainly think it
>> should be documented if consensus is that it stays.  Perhaps an extra option
>> for the defclass to add extra predicates along
>> with :method-invocation-order.
> My natural reaction is to say that those *-list-p predicates shouldn't
> be automatically created, but could someone explain to me in detail
> how/where they're used?
> E.g. I hear it's used for types, but can't we use a type like (list foo)
> instead of foo-list (or maybe (cl-every foo-p) instead of foo-list-p)?
>

I recall back in the day trying something like (list foo) and not 
getting it right so I just wrote a predicate.  I'm not that familiar 
with the nuances of typep, but if there is now a typep built into Emacs, 
EIEIO will need to remove it's local copy of an old typep, and I could 
certainly convert over to using something list (list foo).  I use those 
predicates mostly with typep.

In that case, the eieio-persistent baseclass will need to be updated to 
extract desired classes from the predicates correctly.  The other 
occurrences would be easier to swap in new values.

Eric

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Stefan Monnier]

> I recall back in the day trying something like (list foo) and not getting it
> right so I just wrote a predicate.  I'm not that familiar with the nuances
> of typep, but if there is now a typep built into Emacs,

Not any more than before: there was CL's `typep' and now it's been
renamed to `cl-typep'.

> EIEIO will need to remove it's local copy of an old typep, and I could
> certainly convert over to using something list (list foo).  I use
> those predicates mostly with typep.

Could someone explain (and show) to me in detail how/where these
foo-list-p are used in relation to EIEIO?


        Stefan

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Eric Ludlam]

[-- Attachment #1: Type: text/plain, Size: 1175 bytes --]

On Sun, Sep 21, 2014 at 12:20 PM, Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

>
> > EIEIO will need to remove it's local copy of an old typep, and I could
> > certainly convert over to using something list (list foo).  I use
> > those predicates mostly with typep.
>
> Could someone explain (and show) to me in detail how/where these
> foo-list-p are used in relation to EIEIO?
>
>
>
Sure, in ede/base.el, you will find these lines:

(defclass ede-project (ede-project-placeholder)
  ((subproj :initform nil
    :type list
    :documentation "Sub projects controlled by this project.
For Automake based projects, each directory is treated as a project.")
   (targets :initarg :targets
    :type ede-target-list
    :custom (repeat (object :objectcreatefcn ede-new-target-custom))
    :label "Local Targets"
    :group (targets)
    :documentation "List of top level targets in this project.")


for "targets: you will see:

:type ede-target-list

which will expand to ede-target-list-p, which is a test for a list of type
ede-target.

This also occurs semantic/db.e which tracks a list of tables, and in
cogre.el, where the graph tracks a list of graph elements.

Eric

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bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Stefan Monnier]

> I recall back in the day trying something like (list foo) and not getting it
> right so I just wrote a predicate.

It think that

(cl-deftype list-of (elem-type)
  `(and list
        (satisfies (lambda (list)
                     (cl-every (lambda (elem) (cl-typep elem ',elem-type))
                               list)))))

should work.  I added this definition to eieio-core.el in Emacs's trunk.

> I'm not that familiar with the nuances of typep, but if there is now
> a typep built into Emacs, EIEIO will need to remove it's local copy of
> an old typep,

I removed eieio--typep and used cl-typep instead (one of the benefits
of cl-lib is that it's OK to load it at run time).

> and I could certainly convert over to using something list (list foo).

Please try it.


        Stefan

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Lars Ingebrigtsen]

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

>> I'm not that familiar with the nuances of typep, but if there is now
>> a typep built into Emacs, EIEIO will need to remove it's local copy of
>> an old typep,
>
> I removed eieio--typep and used cl-typep instead (one of the benefits
> of cl-lib is that it's OK to load it at run time).
>
>> and I could certainly convert over to using something list (list foo).
>
> Please try it.

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

This was seven years ago, and apparently defclass still creates the
undocumented -list-p functions.  Is the consensus that they should be
removed?  Perhaps we should generate them as obsolete functions, to
allow third-party usages of them to be notified?

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

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> This was seven years ago, and apparently defclass still creates the
> undocumented -list-p functions.  Is the consensus that they should be
> removed?  Perhaps we should generate them as obsolete functions, to
> allow third-party usages of them to be notified?

AFAIK that's already what we do:

    (when eieio-backward-compatibility
      (let ((csym (intern (concat (symbol-name cname) "-list-p"))))
        (defalias csym
        [...]
        (make-obsolete csym (format
                             "use (cl-typep ... \\='(list-of %s)) instead"
                             cname)
                       "25.1")))

-- Stefan

bug#18494: 24.4.50; defclass creates undocumented *-list-p function

[Lars Ingebrigtsen]

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

> AFAIK that's already what we do:
>
>     (when eieio-backward-compatibility
>       (let ((csym (intern (concat (symbol-name cname) "-list-p"))))
>         (defalias csym
>         [...]
>         (make-obsolete csym (format
>                              "use (cl-typep ... \\='(list-of %s)) instead"
>                              cname)
>                        "25.1")))

Sorry; should have checked first.

Eric Ludlam <eric@siege-engine.com> writes:

>  Could someone explain (and show) to me in detail how/where these
>  foo-list-p are used in relation to EIEIO?
>
> Sure, in ede/base.el, you will find these lines:

[...]

> for "targets: you will see:
>
> :type ede-target-list
>
> which will expand to ede-target-list-p, which is a test for a list of type ede-target.

And this has been fixed, so I guess there's nothing to do here (beyond
removing the -list-p predicates when we start removing things obsoleted
in 25.1 in a couple of years), and I'm therefore closing this bug report.

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