bug#63757: 29.0.91 order of package paths changed: random old versions of packages in load-path

[Philip Kaludercic <philipk@posteo.net>]

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Eli Zaretskii <eliz@gnu.org> writes:

>> From: Stefan Monnier <monnier@iro.umontreal.ca>
>> Cc: Eli Zaretskii <eliz@gnu.org>,  artscan@list.ru,  63757@debbugs.gnu.org
>> Date: Mon, 05 Jun 2023 10:55:50 -0400
>> 
>> > But in this case, if a regular package is upgraded, and a VC package
>> > weren't (even though the user might have written some patch they are
>> > relying on), it would be suddenly switch when starting up Emacs at some
>> > point.
>> 
>> Yup.  AFAIK both behaviors (staying with the VC package, and
>> switching to the non-VC package) can be "incorrect", depending on
>> the circumstances.  So I don't see this as "a bug".
>> 
>> Note also that in the session where we perform the install of the
>> upgraded package, the upgraded package will take precedence over the VC
>> package, so it's mildly more consistent to do the same at startup.
>> 
>> If the user wants to keep using the older VC package, there's always to
>> option to use `package-pinned-packages` or to remove the non-VC package.
>> 
>> If we want to do better, rather than forcing VC packages to the top we
>> should detect when the ordering between VC and non-VC packages changes
>> and emit a warning or prompt the user.
>
> So what's the bottom line here?  Do we have an agreed-upon patch that
> should be installed on the emacs-29 branch?  If so, can it be
> installed soon, please?  Because I'd like to put out another Emacs 29
> pretest in a couple of days.

I think that Stefan's suggestion is the best way to go forward for now:


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From f47c9cdfa4f55a168246bd4fc19ad6c897e8906b Mon Sep 17 00:00:00 2001
From: Philip Kaludercic <philipk@posteo.net>
Date: Wed, 7 Jun 2023 20:37:13 +0200
Subject: [PATCH] ; Restore old behaviour of 'package--get-activatable-pkg'

* lisp/emacs-lisp/package.el (package--get-activatable-pkg): Do not
sort 'package-alist' to prefer VC packages.  (Bug#63757)
---
 lisp/emacs-lisp/package.el | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index 43368b59522..3e6acd9b388 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -924,22 +924,14 @@ package-activate-1
 
 (defun package--get-activatable-pkg (pkg-name)
   ;; Is "activatable" a word?
-  (let ((pkg-descs (sort (cdr (assq pkg-name package-alist))
-                         (lambda (p1 p2)
-                           (let ((v1 (package-desc-version p1))
-                                 (v2 (package-desc-version p2)))
-                             (or
-                              ;; Prefer VC packages.
-                              (package-vc-p p1)
-                              (package-vc-p p2)
-                              ;; Prefer builtin packages.
-                              (package-disabled-p p1 v1)
-                              (not (package-disabled-p p2 v2))))))))
+  (let ((pkg-descs (cdr (assq pkg-name package-alist))))
     ;; Check if PACKAGE is available in `package-alist'.
     (while
         (when pkg-descs
           (let ((available-version (package-desc-version (car pkg-descs))))
-            (package-disabled-p pkg-name available-version)))
+            (or (package-disabled-p pkg-name available-version)
+                ;; Prefer a builtin package.
+                (package-built-in-p pkg-name available-version))))
       (setq pkg-descs (cdr pkg-descs)))
     (car pkg-descs)))
 
-- 
2.39.2


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> If there's no agreement yet, can someone please spell out what is yet
> to be done here?
>
> Thanks.