bug#57676: 29.0.50; Tramp: Unable to close vterm buffer with remote default-directory

[Michael Albinus <michael.albinus@gmx.de>]

James Ferguson <james@faff.org> writes:

Hi James,

> That's definitely what raises the error, though the comment implies to
> me that it's unexpected/undesirable that it is triggered.

Indeed. Your backtrace from the original report shows

> Debugger entered--Lisp error: (file-error "File ‘.’ must be absolute")
>   signal(file-error ("File ‘.’ must be absolute"))
>   tramp-error((tramp-file-name "sshx" nil nil "4x02" nil "." nil) file-error "File `%s' must be absolute" ".")
>   tramp-file-name-unify((tramp-file-name "sshx" nil nil "4x02" nil "." nil) ".")
>   tramp-get-file-property((tramp-file-name "sshx" nil nil "4x02" nil "." nil) "." "file-truename")
>   tramp-flush-file-properties((tramp-file-name "sshx" nil nil "4x02" nil "." nil) ".")
>   tramp-flush-file-function()
>   kill-buffer(#<buffer Terminal-4x02 volta@4x02 (10.0.154.60) - byobu>)

We see, that `tramp-flush-file-properties' is called with
`default-directory' "." in #<buffer Terminal-4x02 volta@4x02 (10.0.154.60) - byobu>

This is obviously an error, because the docstring of `default-directory'
says

--8<---------------cut here---------------start------------->8---
Name of default directory of current buffer.
It should be an absolute directory name; on GNU and Unix systems,
these names start with ‘/’ or ‘~’ and end with ‘/’.
--8<---------------cut here---------------end--------------->8---

Perhaps you could report this to the maintainer of vterm.

For the time being, I've pushed a fix to Emacs master which expands
`default-directory' inside `tramp-flush-file-properties'. Could you,
pls, check?

Best regards, Michael.