bug#63648: 29.0.90; project.el: with switch-use-entire-map, switch-project errors on non-project commands

[Dmitry Gutov <dmitry@gutov.dev>]

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Sorry for the possible duplicate, but it seems this message didn't reach 
the bug tracker, or other recipients. Resending contents below.

On 23/08/2023 20:54, Juri Linkov wrote:
> There is no code where to bind a dynamic variable, because its value
> should be available for the next command in the command loop.
> If you agree there is no other way to implement this than next-default-directory,
> then I could bring up the discussion on emacs-devel.

Before we dive into all that, why not try advice on 'command-execute'? 
For the PoC code at least. It's in Lisp since 2013.

The comment in its body does say "Called directly from the C code", but 
I'm not sure if that has any direct implications for us.

This attached piece of code implements the project-switch-project as you 
outlined. Does it work well for you/others? Careful when testing or 
modifying: a typo can break the command loop (and thus the session).

To me it seems a little too bare-bones, lacking the instructive hints 
project-switch-project currently has.

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(defvar project--next-dd nil)

(defun project--with-next-dd (fun &rest args)
  (advice-remove 'command-execute #'project--with-next-dd)
  (let ((default-directory project--next-dd))
    (apply fun args)))

(defun project-switch-project (dir)
  (interactive (list (funcall project-prompter)))
  (setq project--next-dd dir)
  (advice-add 'command-execute :around #'project--with-next-dd))