bug#61539: 29.0.60; When nnselect-always-regenerate, group info gets out-of-date

[Sean Whitton <spwhitton@spwhitton.name>]

control: tag -1 + patch

Hello,

On Wed 15 Feb 2023 at 12:47PM -07, Sean Whitton wrote:

> 1. Same setup described in #56592, but additionally set
>    nnselect-always-regenerate to t for the groups.
> 2. Enter group.  Mark an unread article as read.
>
>    (length gnus-newsgroup-selection) => 935
>    (car (last (gnus-info-read (gnus-get-info gnus-newsgroup-name))))
>        => (930 . 935)
>
> 3. Exit group.  Enter group again.
>
>    (length gnus-newsgroup-selection) => 934
>    (car (last (gnus-info-read (gnus-get-info gnus-newsgroup-name))))
>        => (930 . 935)
>
> 4. Attempt to exit group again.  Then, while binding select-reads at the
>    beginning of nnselect-push-info, nnselect-categorize signals
>    args-out-of-range, because one of the inline functions it calls
>    attempts to read the 935th element of gnus-newsgroup-selection.

Andrew Cohen sent me the following fix.  I've asked him whether he
thinks this is safe enough for emacs-29.

-- >8 --
From: Andrew Cohen <cohen@bu.edu>

diff --git a/lisp/gnus/nnselect.el b/lisp/gnus/nnselect.el
index 87cb1275313..516433aba93 100644
--- a/lisp/gnus/nnselect.el
+++ b/lisp/gnus/nnselect.el
@@ -350,9 +350,9 @@ nnselect-request-group
     ;; the result.
     (unless nnselect-artlist
       (nnselect-store-artlist group
-       (setq nnselect-artlist (nnselect-generate-artlist group)))
+       (setq nnselect-artlist (nnselect-generate-artlist group))))
       (nnselect-request-update-info
-       group (or info (gnus-get-info group))))
+       group (or info (gnus-get-info group)))
     (if (zerop (setq length (nnselect-artlist-length nnselect-artlist)))
 	(progn
 	  (nnheader-report 'nnselect "Selection produced empty results.")
@@ -880,11 +880,13 @@ nnselect-search-thread
 
 
 
-(defun nnselect-push-info (group)
+(defun nnselect-push-info (_group)
   "Copy mark-lists from GROUP to the originating groups."
   (let ((select-unreads (numbers-by-group gnus-newsgroup-unreads))
 	(select-reads (numbers-by-group
-		       (gnus-info-read (gnus-get-info group)) 'range))
+                       (gnus-sorted-difference gnus-newsgroup-articles
+					       gnus-newsgroup-unreads)
+                       'range))
 	(select-unseen (numbers-by-group gnus-newsgroup-unseen))
 	(gnus-newsgroup-active nil) mark-list)
     ;; collect the set of marked article lists categorized by

-- 
Sean Whitton