bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

[Lars Ingebrigtsen]

`file-attributes' returns a list of data, and you very often see code
like

(let ((atts (file-attributes file)))
  (when (> (elt atts 7) 4000)
    ...))

and you have no idea what that means.  So I think there should be 12
attribute accessor functions (well, defsubsts) that people can use
instead.  The names could be something like `file-attribute-size',
`file-attribute-access-time', etc.



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

bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> `file-attributes' returns a list of data, and you very often see code
> like
>
> (let ((atts (file-attributes file)))
>   (when (> (elt atts 7) 4000)
>     ...))
>
> and you have no idea what that means.  So I think there should be 12
> attribute accessor functions (well, defsubsts) that people can use
> instead.  The names could be something like `file-attribute-size',
> `file-attribute-access-time', etc.

I've now implemented this on the trunk.

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

bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

[Andy Moreton]

On Fri 04 Mar 2016, Lars Ingebrigtsen wrote:

> Lars Ingebrigtsen <larsi@gnus.org> writes:
>
>> `file-attributes' returns a list of data, and you very often see code
>> like
>>
>> (let ((atts (file-attributes file)))
>>   (when (> (elt atts 7) 4000)
>>     ...))
>>
>> and you have no idea what that means.  So I think there should be 12
>> attribute accessor functions (well, defsubsts) that people can use
>> instead.  The names could be something like `file-attribute-size',
>> `file-attribute-access-time', etc.
>
> I've now implemented this on the trunk.

A useful addition. Please fix the defsubst typos (ntf -> nth) and
possibly add some tests.

Consider also fixing file-attributes callers to use the new accessors.

    AndyM

bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

[Lars Magne Ingebrigtsen]

Andy Moreton <andrewjmoreton@gmail.com> writes:

> Consider also fixing file-attributes callers to use the new accessors.

Is there a way to get the byte compiler to output warnings about using
`nth' on output from `file-attributes'?  That would be awesome.  But I
would guess not.  But grepping for "nth.*file-attributes" gives us 180
matches, so somebody who wants to start fixing could...  start...  :-)

Anyway, we probably shouldn't do anything wholesale until 25.1 has been
released (to make merging easier).

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

bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

[Drew Adams]

> Is there a way to get the byte compiler to output warnings about
> using `nth' on output from `file-attributes'?  That would be awesome.  

It would not be awesome.  It would be annoying.
There is nothing to WARN about here.

If you want to control usage for internal Emacs Dev
code then do just that.  But for Emacs-Lisp users
in general this would be completely inappropriate.

bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

[John Wiegley]

>>>>> Drew Adams <drew.adams@oracle.com> writes:

>> Is there a way to get the byte compiler to output warnings about using
>> `nth' on output from `file-attributes'? That would be awesome.

> It would not be awesome. It would be annoying. There is nothing to WARN
> about here.

You could add something of that effect to elint, for example.  I'm not sure if
elint supports "level", or disabling certain warnings, but if it's bad style,
it would be nice to have an indication of it in a non-intrusive way.

-- 
John Wiegley                  GPG fingerprint = 4710 CF98 AF9B 327B B80F
http://newartisans.com                          60E1 46C4 BD1A 7AC1 4BA2

bug#22890: 25.1.50; Wishlist: There should be file-attribute accessors

[Drew Adams]

> >> Is there a way to get the byte compiler to output warnings about
> >> using `nth' on output from `file-attributes'? That would be awesome.
> 
> > It would not be awesome. It would be annoying. There is nothing to
> > WARN about here.
> 
> You could add something of that effect to elint, for example.  I'm
> not sure if elint supports "level", or disabling certain warnings,
> but if it's bad style, it would be nice to have an indication of it
> in a non-intrusive way.

Yes.  Provide it as an (opt-in) option or a command or some other
way for users to get such information on demand.  It's good to be
able to _ask_ for lint-like checks.