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bug#16377: Undo Tree regression: (error "Unrecognized entry in undo list
bug#16377: Undo Tree regression: (error "Unrecognized entry in undo list undo-tree-canary")
Thu, 06 Jul 2017 01:35:54 -0400
Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux)
> + (window-of-current-buffer (get-buffer-window (current-buffer)))
> + (selected-window (selected-window)))
> + (unless (eq window-of-current-buffer selected-window)
Better check (eq (window-buffer) (current-buffer)), since these two
functions are mere accessors, whereas get-buffer-window is a funny
function which returns *one of* the buffer's windows (or nil) and is
hence both more costly (it has a loop inside) and less reliable.
> - (when (or (> (point-min) beg) (< (point-max) end))
> - (error "Changes to be undone are outside visible portion of
> + (when (or (> (point-min) beg) (< (point-max) end))
> + (let ((debug-on-quit nil)
> + (msg (concat
> + "undo-tree--primitive-undo (1 of 4):"
> + " "
> + "Changes to be undone are outside visible portion
> of buffer.")))
> + (signal 'quit `(,msg))))
Not sure what is the benefit of signaling `quit` rather than `error`.
Can you expand on that?
> - ;; Insert might have invalidated some of the markers
> - ;; via modification hooks. Update only the currently
> - ;; valid ones (bug#25599).
> - (if (marker-buffer (car adj))
> - (set-marker (car adj)
> - (- (car adj) (cdr adj)))))))
> + (set-marker (car adj)
> + (- (car adj) (cdr adj))))))
IIUC, this is an unintended change in your code, right?
> ;; (MARKER . OFFSET) means a marker MARKER was adjusted by OFFSET.
> (`(,(and marker (pred markerp)) . ,(and offset (pred integerp)))
> - (warn "Encountered %S entry in undo list with no matching (TEXT .
> POS) entry"
> - next)
> + (let ((msg
> + (concat
> + "undo-tree--primitive-undo: "
> + (format "Encountered %S entry in undo list with no
> matching (TEXT . POS) entry"
> + next))))
> + (message msg))
What is this change meant to do?
> + (_
> + (if (eq next 'undo-tree-canary)
> + (message "undo-tree--primitive-undo: catch-all found `%s'."
> + (error "Unrecognized entry in undo list %S" next)))))
This might make sense to work around the problem, but is clearly not an
actual fix. IIUC Tony said it looked like a bug in undo-tree.
Has there been any progress on finding/fixing the bug there?
What is this "canary" meant to do? If it shouldn't signal an error
here, maybe rather than the constant `undo-tree-canary`, undo-tree
should use another constant value, i.e. one that is a valid (and
harmless) undo entry.