Preserve point when inserting date stamps in ERC

* lisp/erc/erc-stamp.el (erc-stamp-mode, erc-stamp-disable): Move
remaining local teardown business to `erc-stamp--setup' and use
`erc-buffer-do' instead of `erc-with-all-buffers-of-server' to
emphasize that all ERC buffers are affected.
(erc-stamp--insert-date-stamp-as-phony-message): Move `erc--msg-props'
binding to `erc-stamp--lr-date-on-pre-modify'.
(erc-stamp--lr-date-on-pre-modify): Bind `erc--msg-props' here so that
the related guard condition in `erc-add-timestamp' is satisfied and
`erc-insert-timestamp-function' runs.  This fixes a regression new in
ERC 5.6 and introduced by c68dc778 "Manage some text props for ERC
insertion-hook members".  Also, `save-excursion' when narrowing to
prevent point from being dislodged after submitting input at the
prompt.
(erc-insert-timestamp-left-and-right): Don't initialize date stamps
when `erc-timestamp-format-left' is nil or consists only of newlines,
and enable fallback behavior in such cases on behalf of users without
informing them.  Allow global hook members to run first so that those
owned by `scrolltobottom' and similar can see the unadulterated input.
Fix wrong hook name.
(erc-stamp--setup): Fix wrong hook name.  Kill all local vars here
instead of sharing this duty with the minor-mode toggle.  (Bug#60936)

1 files changed, 24 insertions, 19 deletions

diff --git a/lisp/erc/erc-stamp.el b/lisp/erc/erc-stamp.el
index b3812470a4d..412740ac192 100644
--- a/lisp/erc/erc-stamp.el
+++ b/lisp/erc/erc-stamp.el
@@ -187,12 +187,7 @@ from entering them and instead jump over them."
    (remove-hook 'erc-send-modify-hook #'erc-add-timestamp)
    (remove-hook 'erc-mode-hook #'erc-stamp--recover-on-reconnect)
    (remove-hook 'erc--pre-clear-functions #'erc-stamp--reset-on-clear)
-   (erc-with-all-buffers-of-server nil nil
-     (erc-stamp--setup)
-     (kill-local-variable 'erc-stamp--last-stamp)
-     (kill-local-variable 'erc-timestamp-last-inserted)
-     (kill-local-variable 'erc-timestamp-last-inserted-left)
-     (kill-local-variable 'erc-timestamp-last-inserted-right))))
+   (erc-buffer-do #'erc-stamp--setup)))
 
 (defvar erc-stamp--invisible-property nil
   "Existing `invisible' property value and/or symbol `timestamp'.")
@@ -664,11 +659,7 @@ printed just after each line's text (no alignment)."
 (defun erc-stamp--insert-date-stamp-as-phony-message (string)
   (cl-assert (string-empty-p string))
   (setq string erc-stamp--current-datestamp-left)
-  (cl-assert string)
   (let ((erc-stamp--skip t)
-        (erc--msg-props (map-into `((erc-msg . datestamp)
-                                    (erc-ts . ,(erc-stamp--current-time)))
-                                  'hash-table))
         (erc-insert-modify-hook `(,@erc-insert-modify-hook
                                   erc-stamp--propertize-left-date-stamp))
         ;; Don't run hooks that aren't expecting a narrowed buffer.
@@ -684,11 +675,17 @@ printed just after each line's text (no alignment)."
              (erc-stamp--current-datestamp-left rendered)
              (erc-insert-timestamp-function
               #'erc-stamp--insert-date-stamp-as-phony-message))
-    (save-restriction
-      (narrow-to-region (or erc--insert-marker erc-insert-marker)
-                        (or erc--insert-marker erc-insert-marker))
-      (let (erc-timestamp-format erc-away-timestamp-format)
-        (erc-add-timestamp)))))
+    (save-excursion
+      (save-restriction
+        (narrow-to-region (or erc--insert-marker erc-insert-marker)
+                          (or erc--insert-marker erc-insert-marker))
+        ;; Forget current `erc-cmd', etc.
+        (let ((erc--msg-props
+               (map-into `((erc-msg . datestamp)
+                           (erc-ts . ,(erc-stamp--current-time)))
+                         'hash-table))
+              erc-timestamp-format erc-away-timestamp-format)
+          (erc-add-timestamp))))))
 
 (defvar erc-stamp-prepend-date-stamps-p nil
   "When non-nil, date stamps are not independent messages.
@@ -714,9 +711,13 @@ requirements related to `erc-legacy-invisible-bounds-p'.
 Additionally, ensure every date stamp is identifiable as such so
 that internal modules can easily distinguish between other
 left-sided stamps and date stamps inserted by this function."
-  (unless (or erc-stamp--date-format-end erc-stamp-prepend-date-stamps-p)
-    (add-hook 'erc-insert-pre-hook #'erc-stamp--lr-date-on-pre-modify -95 t)
-    (add-hook 'erc-send-pre-functions #'erc-stamp--lr-date-on-pre-modify -95 t)
+  (unless (or erc-stamp--date-format-end erc-stamp-prepend-date-stamps-p
+              (and (or (null erc-timestamp-format-left)
+                       (string-empty-p ; compat
+                        (string-trim erc-timestamp-format-left "\n")))
+                   (setq erc-stamp-prepend-date-stamps-p t)))
+    (add-hook 'erc-insert-pre-hook #'erc-stamp--lr-date-on-pre-modify 10 t)
+    (add-hook 'erc-pre-send-functions #'erc-stamp--lr-date-on-pre-modify 10 t)
     (let ((erc--insert-marker (point-min-marker))
           (end-marker (point-max-marker)))
       (set-marker-insertion-type erc--insert-marker t)
@@ -817,7 +818,11 @@ Return the empty string if FORMAT is nil."
       (erc-munge-invisibility-spec))
     ;; Undo local mods from `erc-insert-timestamp-left-and-right'.
     (remove-hook 'erc-insert-pre-hook #'erc-stamp--lr-date-on-pre-modify t)
-    (remove-hook 'erc-send-pre-functions #'erc-stamp--lr-date-on-pre-modify t)
+    (remove-hook 'erc-pre-send-functions #'erc-stamp--lr-date-on-pre-modify t)
+    (kill-local-variable 'erc-stamp--last-stamp)
+    (kill-local-variable 'erc-timestamp-last-inserted)
+    (kill-local-variable 'erc-timestamp-last-inserted-left)
+    (kill-local-variable 'erc-timestamp-last-inserted-right)
     (kill-local-variable 'erc-stamp--date-format-end)))
 
 (defun erc-hide-timestamps ()