5 files changed, 77 insertions, 13 deletions

diff --git a/lisp/erc/erc-button.el b/lisp/erc/erc-button.el
index a62dd520860..c290e76843c 100644
--- a/lisp/erc/erc-button.el
+++ b/lisp/erc/erc-button.el
@@ -829,6 +829,7 @@ argument when calling `erc-display-message'.  Otherwise, add it
 to STRINGS.  If STRINGS contains any trailing non-nil
 non-strings, concatenate leading string members before applying
 `format'.  Otherwise, just concatenate everything."
+  (defvar erc-stamp--skip)
   (let* ((buffer (if (bufferp maybe-buffer)
                      maybe-buffer
                    (when (stringp maybe-buffer)
@@ -844,8 +845,10 @@ non-strings, concatenate leading string members before applying
                  (push head strings))
                #'format))
          (string (apply op strings))
-         (erc-insert-modify-hook (remove 'erc-add-timestamp
-                                         erc-insert-modify-hook))
+         ;; Avoid timestamps unless left-sided.
+         (erc-stamp--skip (or (bound-and-true-p erc-stamp--display-margin-mode)
+                              (not (fboundp 'erc-timestamp-offset))
+                              (zerop (erc-timestamp-offset))))
          (erc-insert-post-hook
           (cons (lambda ()
                   (setq string (buffer-substring (point-min)
diff --git a/lisp/erc/erc-log.el b/lisp/erc/erc-log.el
index 79fece5779e..5efde6cad11 100644
--- a/lisp/erc/erc-log.el
+++ b/lisp/erc/erc-log.el
@@ -231,7 +231,7 @@ also be a predicate function.  To only log when you are not set away, use:
    (add-hook 'erc-part-hook #'erc-conditional-save-buffer)
    ;; append, so that 'erc-initialize-log-marker runs first
    (add-hook 'erc-connect-pre-hook #'erc-log-setup-logging 'append)
-   (add-hook 'erc--pre-clear-functions #'erc-save-buffer-in-logs)
+   (add-hook 'erc--pre-clear-functions #'erc-save-buffer-in-logs 50)
    (dolist (buffer (erc-buffer-list))
      (erc-log-setup-logging buffer))
    (erc--modify-local-map t "C-c C-l" #'erc-save-buffer-in-logs))
@@ -430,7 +430,8 @@ You can save every individual message by putting this function on
               (if (and erc-truncate-buffer-on-save
                        (called-interactively-p 'interactive))
                   (let ((erc-log--save-in-progress-p t))
-                    (erc-cmd-CLEAR)
+                    (save-excursion (goto-char erc-insert-marker)
+                                    (erc-cmd-CLEAR))
                     (erc-button--display-error-notice-with-keys
                      (erc-server-buffer) "Option `%s' is deprecated."
                      " Use /CLEAR instead." 'erc-truncate-buffer-on-save))
diff --git a/lisp/erc/erc-stamp.el b/lisp/erc/erc-stamp.el
index 9ca3ea320a0..a65b564ba6c 100644
--- a/lisp/erc/erc-stamp.el
+++ b/lisp/erc/erc-stamp.el
@@ -182,7 +182,7 @@ from entering them and instead jump over them."
    (add-hook 'erc-insert-modify-hook #'erc-add-timestamp 70)
    (add-hook 'erc-send-modify-hook #'erc-add-timestamp 70)
    (add-hook 'erc-mode-hook #'erc-stamp--recover-on-reconnect)
-   (add-hook 'erc--pre-clear-functions #'erc-stamp--reset-on-clear)
+   (add-hook 'erc--pre-clear-functions #'erc-stamp--reset-on-clear 40)
    (unless erc--updating-modules-p (erc-buffer-do #'erc-stamp--setup)))
   ((remove-hook 'erc-mode-hook #'erc-munge-invisibility-spec)
    (remove-hook 'erc-insert-modify-hook #'erc-add-timestamp)
@@ -973,8 +973,9 @@ with the option `erc-echo-timestamps', see the companion option
 (defun erc-stamp--reset-on-clear (pos)
   "Forget last-inserted stamps when POS is at insert marker."
   (when (= pos (1- erc-insert-marker))
-    (add-hook 'erc-stamp--insert-date-hook
-              #'erc-stamp--update-saved-position 0 t)
+    (when erc-stamp--date-mode
+      (add-hook 'erc-stamp--insert-date-hook
+                #'erc-stamp--update-saved-position 0 t))
     (setq erc-timestamp-last-inserted nil
           erc-timestamp-last-inserted-left nil
           erc-timestamp-last-inserted-right nil)))
diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 64629026704..6eee8bcae92 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -4160,12 +4160,16 @@ If no USER argument is specified, list the contents of `erc-ignore-list'."
 Called with position indicating boundary of interval to be excised.")
 
 (defun erc-cmd-CLEAR ()
-  "Clear the window content."
-  (let ((inhibit-read-only t))
-    (run-hook-with-args 'erc--pre-clear-functions (1- erc-insert-marker))
-    ;; Ostensibly, `line-beginning-position' is for use in lisp code.
-    (delete-region (point-min) (min (line-beginning-position)
-                                    (1- erc-insert-marker))))
+  "Clear messages in current buffer after informing active modules.
+Expect modules to perform housekeeping tasks to withstand the
+disruption.  When called from lisp code, only clear messages up
+to but not including the one occupying the current line."
+  (with-silent-modifications
+    (let ((max (if (>= (point) erc-insert-marker)
+                   (1- erc-insert-marker)
+                 (or (erc--get-inserted-msg-bounds 'beg) (pos-bol)))))
+      (run-hook-with-args 'erc--pre-clear-functions max)
+      (delete-region (point-min) max)))
   t)
 (put 'erc-cmd-CLEAR 'process-not-needed t)
 
diff --git a/test/lisp/erc/erc-scenarios-log.el b/test/lisp/erc/erc-scenarios-log.el
index cd28ea54b2e..cff88d59c85 100644
--- a/test/lisp/erc/erc-scenarios-log.el
+++ b/test/lisp/erc/erc-scenarios-log.el
@@ -206,4 +206,59 @@
     (erc-truncate-mode -1)
     (when noninteractive (delete-directory tempdir :recursive))))
 
+(defvar erc-insert-timestamp-function)
+(declare-function erc-insert-timestamp-left "erc-stamp" (string))
+
+(ert-deftest erc-scenarios-log--save-buffer-in-logs/truncate-on-save ()
+  :tags '(:expensive-test)
+  (erc-scenarios-common-with-cleanup
+      ((erc-scenarios-common-dialog "base/assoc/bouncer-history")
+       (dumb-server (erc-d-run "localhost" t 'foonet))
+       (tempdir (make-temp-file "erc-tests-log." t nil nil))
+       (erc-log-channels-directory tempdir)
+       (erc-modules (cons 'log erc-modules))
+       (port (process-contact dumb-server :service))
+       (erc-truncate-buffer-on-save t)
+       (logchan (expand-file-name (format "#chan!tester@127.0.0.1:%d.txt" port)
+                                  tempdir))
+       (erc-server-flood-penalty 0.1)
+       (erc-insert-timestamp-function #'erc-insert-timestamp-left)
+       (expect (erc-d-t-make-expecter)))
+
+    (unless noninteractive
+      (add-hook 'kill-emacs-hook
+                (lambda () (delete-directory tempdir :recursive))))
+
+    (ert-info ("Connect to foonet")
+      (with-current-buffer (erc :server "127.0.0.1"
+                                :port port
+                                :nick "tester"
+                                :password "foonet:changeme"
+                                :full-name "tester")
+        (should (string= (buffer-name) (format "127.0.0.1:%d" port)))))
+
+    (with-current-buffer (erc-d-t-wait-for 5 (get-buffer "#chan"))
+      (funcall expect 10 "<someone> [07:04:10] hi everyone")
+      (should-not (file-exists-p logchan))
+      ;; Simulate an M-x erc-save-buffer-in-logs RET
+      (cl-letf (((symbol-function 'called-interactively-p) #'always))
+        (call-interactively #'erc-save-buffer-in-logs))
+      (should (file-exists-p logchan))
+      (funcall expect 10 "<alice> bob: As't please your lordship")
+      (erc-save-buffer-in-logs)
+      ;; Not truncated when called by lisp code.
+      (should (> (buffer-size) 400)))
+
+    (ert-info ("No double entries")
+      (with-temp-buffer
+        (insert-file-contents logchan)
+        (funcall expect 0.1 "hi everyone")
+        (funcall expect -0.1 "hi everyone")
+        (funcall expect 0.1 "Playback Complete")
+        (funcall expect -0.1 "Playback Complete")
+        (funcall expect 10 "<alice> bob: As't")))
+
+    (erc-log-mode -1)
+    (when noninteractive (delete-directory tempdir :recursive))))
+
 ;;; erc-scenarios-log.el ends here