Ignore date stamps completely in erc-track

* etc/ERC-NEWS: Mention that date stamps no longer optionally affect
the mode line.  Also mention but discourage new variable
'erc-stamp-prepend-date-stamps-p'.
* lisp/erc/erc-stamp.el (erc-stamp-prepend-date-stamps-p): New
variable, an escape hatch to allow date stamps to once again be
prepended to messages.
(erc-insert-timestamp-left-and-right): Don't insert stamps as
independent messages when legacy support flag
`erc-stamp-prepend-date-stamps-p' is non-nil.
* lisp/erc/erc-track.el (erc-track--skipped-msgs): New internal
variable.
(erc-track-modified-channels): In previous versions, a date stamp
attached to a message for an IRC command in `erc-track-exclude-types'
would have no effect on the mode line.  That they were able to
otherwise was probably a bug.  Regardless, this distinction was lost
for the worse after date stamps became independent messages with
c68dc7786f "Manage some text props for ERC insertion-hook members".
To sidestep this regression, the `track' module will ignore date
stamps completely from now on.  Thanks to Corwin Brust for spotting
this.
* test/lisp/erc/erc-scenarios-stamp.el
(erc-scenarios-stamp--left/display-margin-mode): Remove redundant
binding.
(erc-scenarios-stamp--legacy-date-stamps): New test.  (Bug#60936)

etc/ERC-NEWS

@@ -228,6 +228,12 @@ with a legitimate use for this option likely also possesses the
 knowledge to rig up a suitable analog with minimal effort.  That said,
 the road to removal is long.
 
+** The 'track' module always ignores date stamps.
+Users of the stamp module who leave 'erc-insert-timestamp-function'
+set to its default of 'erc-insert-timestamp-left-and-right' will find
+that date stamps no longer affect the mode line, even for IRC commands
+not included in 'erc-track-exclude-types'.
+
 ** Option 'erc-warn-about-blank-lines' is more informative.
 Enabled by default, this option now produces more useful feedback
 whenever ERC rejects prompt input containing whitespace-only lines.
@@ -348,7 +354,9 @@ leading portion of message bodies as well as special casing to act on
 these areas without inflicting collateral damage.  It may also be
 worth noting that as consequence of these changes, the internally
 managed variable 'erc-timestamp-last-inserted-left' no longer records
-the final trailing newline in 'erc-timestamp-format-left'.
+the final trailing newline in 'erc-timestamp-format-left'.  If you
+must, see variable 'erc-stamp-prepend-date-stamps-p' for a temporary
+escape hatch.
 
 *** The role of a module's Custom group is now more clearly defined.
 Associating built-in modules with Custom groups and provided library

lisp/erc/erc-stamp.el

@@ -689,6 +689,16 @@ printed just after each line's text (no alignment)."
       (let (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.
+Users should think twice about enabling this escape hatch.  It
+will likely degraded the user experience by causing post-5.5
+features, like `fill-wrap', dynamic invisibility, etc., to
+malfunction.  Basic support for the default configuration may
+expire earlier than normally expected.")
+(make-obsolete-variable 'erc-stamp-prepend-date-stamps-p
+                        "unsupported legacy behavior" "30.1")
+
 (defun erc-insert-timestamp-left-and-right (string)
   "Insert a stamp on either side when it changes.
 When the deprecated option `erc-timestamp-format-right' is nil,
@@ -703,7 +713,7 @@ 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 erc-stamp--date-format-end
+  (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)
     (let ((erc--insert-marker (point-min-marker))
@@ -719,6 +729,13 @@ left-sided stamps and date stamps inserted by this function."
                      (if erc-timestamp-format-right
                          (erc-format-timestamp ct erc-timestamp-format-right)
                        string))))
+    ;; Maybe insert legacy date stamp.
+    (when-let ((erc-stamp-prepend-date-stamps-p)
+               (ts-left (erc-format-timestamp ct erc-timestamp-format-left))
+               ((not (string= ts-left erc-timestamp-last-inserted-left))))
+      (goto-char (point-min))
+      (erc-put-text-property 0 (length ts-left) 'field 'erc-timestamp ts-left)
+      (insert (setq erc-timestamp-last-inserted-left ts-left)))
     ;; insert right timestamp
     (let ((erc-timestamp-only-if-changed-flag t)
 	  (erc-timestamp-last-inserted erc-timestamp-last-inserted-right))

lisp/erc/erc-track.el

@@ -785,6 +785,9 @@ that face with highest priority in NEW-FACES is also a member of
               choice))
         choice))))
 
+(defvar erc-track--skipped-msgs '(datestamp)
+  "Values of `erc-msg' text prop to ignore.")
+
 (defun erc-track-modified-channels ()
   "Hook function for `erc-insert-post-hook'.
 Check if the current buffer should be added to the mode line as a
@@ -798,10 +801,13 @@ the current buffer is in `erc-mode'."
                        ;; FIXME either use `erc--server-buffer-p' or
                        ;; explain why that's unwise.
                        (erc-server-or-unjoined-channel-buffer-p)))
-	     (not (erc-message-type-member
-		   (or (erc-find-parsed-property)
-		       (point-min))
-		   erc-track-exclude-types)))
+             (not (let ((parsed (erc-find-parsed-property)))
+                    (or (erc-message-type-member (or parsed (point-min))
+                                                 erc-track-exclude-types)
+                        ;; Skip certain non-server-sent messages.
+                        (and (not parsed)
+                             (erc--check-msg-prop 'erc-msg
+                                                  erc-track--skipped-msgs))))))
 	;; If the active buffer is not visible (not shown in a
 	;; window), and not to be excluded, determine the kinds of
 	;; faces used in the current message, and unless the user

test/lisp/erc/erc-scenarios-stamp.el

@@ -50,7 +50,6 @@
        (erc-stamp--current-time 704591940)
        (erc-stamp--tz t)
        (erc-server-flood-penalty 0.1)
-       (erc-timestamp-only-if-changed-flag nil)
        (erc-insert-timestamp-function #'erc-insert-timestamp-left)
        (erc-modules (cons 'fill-wrap erc-modules))
        (erc-timestamp-only-if-changed-flag nil)
@@ -87,4 +86,31 @@
             (should (looking-back "CEIMRUabefhiklmnoqstuv\n"))
             (should (looking-at (rx "[")))))))))
 
+(ert-deftest erc-scenarios-stamp--legacy-date-stamps ()
+  (with-suppressed-warnings ((obsolete erc-stamp-prepend-date-stamps-p))
+    (erc-scenarios-common-with-cleanup
+        ((erc-scenarios-common-dialog "base/reconnect")
+         (erc-stamp-prepend-date-stamps-p t)
+         (dumb-server (erc-d-run "localhost" t 'unexpected-disconnect))
+         (port (process-contact dumb-server :service))
+         (erc-server-flood-penalty 0.1)
+         (expect (erc-d-t-make-expecter)))
+
+      (ert-info ("Connect")
+        (with-current-buffer (erc :server "127.0.0.1"
+                                  :port port
+                                  :full-name "tester"
+                                  :nick "tester")
+          (funcall expect 5 "Opening connection")
+          (goto-char (1- (match-beginning 0)))
+          (should (eq 'erc-timestamp (field-at-pos (point))))
+          (should (eq 'unknown (erc--get-inserted-msg-prop 'erc-msg)))
+          ;; Force redraw of date stamp.
+          (setq erc-timestamp-last-inserted-left nil)
+
+          (funcall expect 5 "This server is in debug mode")
+          (while (and (zerop (forward-line -1))
+                      (not (eq 'erc-timestamp (field-at-pos (point))))))
+          (should (erc--get-inserted-msg-prop 'erc-cmd)))))))
+
 ;;; erc-scenarios-stamp.el ends here