GNU bug report logs - #17403
24.4.50; package-alist doc-string error

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Message #11 received at 17403 <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> gmail.com>
To: Stefan Kangas <stefan <at> marxist.se>
Cc: 17403 <at> debbugs.gnu.org, Richard Kim <emacs18 <at> gmail.com>
Subject: Re: bug#17403: 24.4.50; package-alist doc-string error
Date: Sun, 14 Jul 2019 10:26:36 -0400

Stefan Kangas <stefan <at> marxist.se> writes:

> Richard Kim <emacs18 <at> gmail.com> writes:
>
>> I believe the doc-string for package-alist is incorrect.
>> Each element is (PKG DESCS) rather than (PKG . DESCS), i.e.,
>> each item is (list PKG DESCS) rather than (cons PKG DESCS).
>> To fix this, the patch shown below can be applied.
>
> You are correct.  There is indeed a difference between what the
> documentation says and what the code does.  According to the code,
> package-alist is *not* an alist, but a list of lists. (This goes back
> to at least 2013 AFAICT.)
>
> Yet it has the suffix "-alist".

The only structural requirement for "alist"ness is to be a list of
conses.  As long as none of the lists are empty, a list of lists is (or
can be viewed as) an alist.  I don't think there is a bug here, just a
misunderstanding of dot notation.

>> My assertion is confirmed by the following code from package.el:
>> 
>>     (defun package-process-define-package (exp origin)
>>        ...
>>             ;; If there's no old package, just add this to `package-alist'.
>>             (push (list name new-pkg-desc) package-alist)

Note that this is equivalent to this:

    (push (cons name (list new-pkg-desc)) package-alist)

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