bug#63338: 29.0.90; package-vc-install'ing the same package multiple times results in duplication in package-selected-packages

[Philip Kaludercic <philipk@posteo.net>]

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Jimmy Wong <wyuenho@gmail.com> writes:

> I don’t think you should dedup the variable that could have been
> modified by something else such as package-install. This may make
> debugging harder should package.el itself introduce a bug that
> duplicates pacakages in the variable. How about just using good old
> add-to-list?

The issue is that we want to go through package--save-selected-packages,
that is given a new value to assign to `package-selected-packages'.
An otherwise, I my understanding is that add-to-list is not conventional
in executed code.

The alternative is to check for duplicates before invoking the function:


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diff --git a/lisp/emacs-lisp/package-vc.el b/lisp/emacs-lisp/package-vc.el
index e9794eac783..b967aaa3d4d 100644
--- a/lisp/emacs-lisp/package-vc.el
+++ b/lisp/emacs-lisp/package-vc.el
@@ -507,9 +507,10 @@ package-vc--unpack-1
         (package--reload-previously-loaded new-desc)))
 
     ;; Mark package as selected
-    (package--save-selected-packages
-     (cons (package-desc-name pkg-desc)
-           package-selected-packages))
+    (let ((name (package-desc-name pkg-desc)))
+      (unless (memq name package-selected-packages)
+        (package--save-selected-packages
+         (cons name package-selected-packages))))
     (package--quickstart-maybe-refresh)
 
     ;; Confirm that the installation was successful

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> On 8 May 2023 at 1:03 PM +0100, Eli Zaretskii <eliz@gnu.org>, wrote:
>> > Cc: 63338@debbugs.gnu.org
>> > From: Philip Kaludercic <philipk@posteo.net>
>> > Date: Mon, 08 May 2023 10:36:55 +0000
>> >
>> > Jimmy Yuen Ho Wong <wyuenho@gmail.com> writes:
>> >
>> > > Reproduction:
>> > >
>> > > 0. (setq custom-file (const user-emacs-directory "custom.el"))
>> > > 1. M-x package-vc-install company
>> > > 2. M-x package-vc-install company RET y
>> > > 3. C-x C-f ~/.emacs/custom.el
>> > > 4. Observe that `company` has been listed twice under
>> > > `package-selected-packages`.
>> > >
>> > > Expectation:
>> > >
>> > > Installing the same package twice should not result in its duplication
>> > > in `package-selected-packages`.
>> >
>> > An easy fix would be just to ensure that package-selected-packages is
>> > always deduplicated before assigning the value:
>>
>> This is OK for the emacs-29 branch, thanks.