Ensure that nnimap doesn't send too long lines to the server

* lisp/gnus/nnimap.el (nnimap-retrieve-headers): Don't send
too-long lines to the server (bug#56138).

1 files changed, 15 insertions, 6 deletions

diff --git a/lisp/gnus/nnimap.el b/lisp/gnus/nnimap.el
index afd5418912f..c158367b736 100644
--- a/lisp/gnus/nnimap.el
+++ b/lisp/gnus/nnimap.el
@@ -239,12 +239,21 @@ during splitting, which may be slow."
     (when (nnimap-change-group group server)
       (with-current-buffer (nnimap-buffer)
         (erase-buffer)
-        (nnimap-wait-for-response
-         (nnimap-send-command
-          "UID FETCH %s %s"
-          (nnimap-article-ranges (gnus-compress-sequence articles))
-          (nnimap-header-parameters))
-         t)
+        (let ((ranges (gnus-compress-sequence articles))
+              sequence)
+          ;; If we have a lot of ranges, split them up to avoid
+          ;; generating too-long lines.  (The limit is 8192 octects,
+          ;; and this should guarantee that it's (much) shorter than
+          ;; that.)
+          (while ranges
+            (setq sequence
+                  (nnimap-send-command
+                   "UID FETCH %s %s"
+                   (nnimap-article-ranges (seq-take ranges 200))
+                   (nnimap-header-parameters)))
+            (setq ranges (nthcdr 200 ranges)))
+          ;; Wait for the final one.
+          (nnimap-wait-for-response sequence t))
         (unless (process-live-p (get-buffer-process (current-buffer)))
           (error "IMAP server %S closed connection" nnimap-address))
         (nnimap-transform-headers)