bug#81531: 30.2; filenotify: moving file out of watched directory delays the "deleted" event until file is later moved back in

Michael Albinus <[email protected]> writes:

Hi,

> This is the problematic action. We get from inotify only a 'moved-from
> "bar"' event. The corresponding 'moved-to' event is not returned,
> because the file path is ouside of the watched directory.
>
> filenotify.el is instructed, to wait for the next backend event after
> 'moved-from'. This is needed to decide what to do. Since no second
> backend event arrives, nothing is sent to the handler. This is what you
> have observed.

FTR, if you have two independent file watchers over directories, and you
move a file between these two directories, filenotify.el detects this as
rename, and reports it twice in both callbacks. See this scenario:

# mkdir foo
# mkdir bar
# ~/src/emacs/src/emacs -l filenotify --eval "(setq file-notify-debug t)" --eval "(file-notify-add-watch \"foo\" '(change) #'ignore)" --eval "(file-notify-add-watch \"bar\" '(change) #'ignore)" &
# touch foo/baz

--8<---------------cut here---------------start------------->8---
file-notify-handle-event (file-notify ((1 . 0) (create) "baz" 0) file-notify--callback-inotify)
file-notify--call-handler (1 . 0) created "/home/albinus/.emacs.d/foo/baz" nil #s(file-notify--watch "/home/albinus/.emacs.d/foo" nil ignore) "/home/albinus/.emacs.d/foo" "/home/albinus/.emacs.d/foo"
--8<---------------cut here---------------end--------------->8---

# mv foo/baz bar/

--8<---------------cut here---------------start------------->8---
file-notify-handle-event (file-notify ((1 . 0) (moved-from) "baz" 1134534) file-notify--callback-inotify)
file-notify-handle-event (file-notify ((2 . 0) (moved-to) "baz" 1134534) file-notify--callback-inotify)
file-notify--call-handler (1 . 0) renamed "/home/albinus/.emacs.d/foo/baz" "/home/albinus/.emacs.d/bar/baz" #s(file-notify--watch "/home/albinus/.emacs.d/foo" nil ignore) "/home/albinus/.emacs.d/foo" "/home/albinus/.emacs.d/foo"
file-notify--call-handler (2 . 0) renamed "/home/albinus/.emacs.d/foo/baz" "/home/albinus/.emacs.d/bar/baz" #s(file-notify--watch "/home/albinus/.emacs.d/bar" nil ignore) "/home/albinus/.emacs.d/bar" "/home/albinus/.emacs.d/bar"
--8<---------------cut here---------------end--------------->8---

# rm -rf foo bar

--8<---------------cut here---------------start------------->8---
file-notify-handle-event (file-notify ((1 . 0) (delete-self) "/home/albinus/.emacs.d/foo" 0) file-notify--callback-inotify)
file-notify--call-handler (1 . 0) deleted "/home/albinus/.emacs.d/foo" nil #s(file-notify--watch "/home/albinus/.emacs.d/foo" nil ignore) "/home/albinus/.emacs.d/foo" "/home/albinus/.emacs.d/foo"
file-notify-handle-event (file-notify ((1 . 0) (ignored) "/home/albinus/.emacs.d/foo" 0) file-notify--callback-inotify)
file-notify-handle-event (file-notify ((1 . 0) stopped "/home/albinus/.emacs.d/foo") ignore)
file-notify-handle-event (file-notify ((2 . 0) (delete) "baz" 0) file-notify--callback-inotify)
file-notify--call-handler (2 . 0) deleted "/home/albinus/.emacs.d/bar/baz" nil #s(file-notify--watch "/home/albinus/.emacs.d/bar" nil ignore) "/home/albinus/.emacs.d/bar" "/home/albinus/.emacs.d/bar"
file-notify-handle-event (file-notify ((2 . 0) (delete-self) "/home/albinus/.emacs.d/bar" 0) file-notify--callback-inotify)
file-notify--call-handler (2 . 0) deleted "/home/albinus/.emacs.d/bar" nil #s(file-notify--watch "/home/albinus/.emacs.d/bar" nil ignore) "/home/albinus/.emacs.d/bar" "/home/albinus/.emacs.d/bar"
file-notify-handle-event (file-notify ((2 . 0) (ignored) "/home/albinus/.emacs.d/bar" 0) file-notify--callback-inotify)
file-notify-handle-event (file-notify ((2 . 0) stopped "/home/albinus/.emacs.d/bar") ignore)
--8<---------------cut here---------------end--------------->8---

See the different watch descriptors (1 . 0)  and (2 . 0)

This works only for the inotify backend.

Best regards, Michael.