Fix streaming problems in nnimap-retrieve-headers

* lisp/gnus/nnimap.el (nnimap-retrieve-headers): Don't stream the
UID FETCH commands, since the server may return the results
out-of-order (bug#56332).

1 files changed, 14 insertions, 16 deletions

diff --git a/lisp/gnus/nnimap.el b/lisp/gnus/nnimap.el
index 22edc3c72cf..c629cb85d96 100644
--- a/lisp/gnus/nnimap.el
+++ b/lisp/gnus/nnimap.el
@@ -241,22 +241,20 @@ during splitting, which may be slow."
     (when (nnimap-change-group group server)
       (with-current-buffer (nnimap-buffer)
         (erase-buffer)
-        (let ((ranges (gnus-compress-sequence articles t))
-              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 nnimap--max-retrieve-headers))
-                   (nnimap-header-parameters)))
-            (setq ranges (nthcdr nnimap--max-retrieve-headers ranges)))
-          ;; Wait for the final one.
-          (nnimap-wait-for-response sequence t))
+        ;; 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.)  We don't stream the requests, since the server
+        ;; may respond to the requests out-of-order:
+        ;; https://datatracker.ietf.org/doc/html/rfc3501#section-5.5
+        (dolist (ranges (seq-split (gnus-compress-sequence articles t)
+                                   nnimap--max-retrieve-headers))
+          (nnimap-wait-for-response
+           (nnimap-send-command
+            "UID FETCH %s %s"
+            (nnimap-article-ranges ranges)
+            (nnimap-header-parameters))
+           t))
         (unless (process-live-p (get-buffer-process (current-buffer)))
           (error "IMAP server %S closed connection" nnimap-address))
         (nnimap-transform-headers)