From 634cedfea17a8caa7d93627b233a2eef19fc43fb Mon Sep 17 00:00:00 2001
From: Andrew G Cohen <cohen@andy.bu.edu>
Date: Fri, 4 Feb 2022 08:30:32 +0800
Subject: [PATCH] Improve compression of article lists in gnus/nnselect

* lisp/gnus/nnselect.el (nnselect-compress-artlist): Allow compressed list.
nnselect-uncompress-artlist): Properly loop over rsv values.
---
 lisp/gnus/nnselect.el | 39 +++++++++++++++++++++------------------
 1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/lisp/gnus/nnselect.el b/lisp/gnus/nnselect.el
index 205456a57df..85df0284ef1 100644
--- a/lisp/gnus/nnselect.el
+++ b/lisp/gnus/nnselect.el
@@ -79,30 +79,33 @@
 ;;; Helper routines.
 (defun nnselect-compress-artlist (artlist)
   "Compress ARTLIST."
-  (let (selection)
-    (pcase-dolist (`(,artgroup . ,arts)
-                   (nnselect-categorize artlist #'nnselect-artitem-group))
-      (let (list)
-        (pcase-dolist (`(,rsv . ,articles)
-                       (nnselect-categorize
-                        arts #'nnselect-artitem-rsv #'nnselect-artitem-number))
-          (push (cons rsv (gnus-compress-sequence (sort articles #'<)))
-                list))
-        (push (cons artgroup list) selection)))
-    selection))
+  (if (consp artlist)
+      artlist
+    (let (selection)
+      (pcase-dolist (`(,artgroup . ,arts)
+                     (nnselect-categorize artlist #'nnselect-artitem-group))
+	(let (list)
+          (pcase-dolist (`(,rsv . ,articles)
+			 (nnselect-categorize
+                          arts #'nnselect-artitem-rsv #'nnselect-artitem-number))
+            (push (cons rsv (gnus-compress-sequence (sort articles #'<)))
+                  list))
+          (push (cons artgroup list) selection)))
+      selection)))
 
 (defun nnselect-uncompress-artlist (artlist)
   "Uncompress ARTLIST."
   (if (vectorp artlist)
       artlist
     (let (selection)
-      (pcase-dolist (`(,artgroup (,artrsv . ,artseq)) artlist)
-	(setq selection
-	      (vconcat
-	       (cl-map 'vector
-                       (lambda (art)
-                         (vector artgroup art artrsv))
-		    (gnus-uncompress-sequence artseq)) selection)))
+      (pcase-dolist (`(,artgroup . ,list) artlist)
+	(pcase-dolist (`(,artrsv . ,artseq) list)
+	  (setq selection
+		(vconcat
+		 (cl-map 'vector
+			 (lambda (art)
+                           (vector artgroup art artrsv))
+			 (gnus-uncompress-sequence artseq)) selection))))
       selection)))
 
 (make-obsolete 'nnselect-group-server 'gnus-group-server "28.1")
-- 
2.39.5