project-find-file completion and navigation

Question

I am learning to use project-find-file. I know there are better alternatives in melpa, but I would like to learn the "out of the box" functionality.

When I do project-find-file, start typing a filename, then TAB, I get a completion buffer. I expected to be able to navigate in that buffer with arrows, and C-n/C-p. Is it possible to set it up like that, or is this just a limitation of the tool?

If it's just not possible, I'd be ok to use ido for this.

Here is my current config for ido:

(ido-mode 'both) ;; for buffers and files
(setq
  ido-save-directory-list-file "~/.emacs.d/cache/ido.last"

  ido-ignore-buffers ;; ignore these guys
  '("\\` " "^\*Mess" "^\*Back" ".*Completion" "^\*Ido" "^\*trace"
     "^\*compilation" "^\*GTAGS" "^session\.*" "\*GNU Emacs\*")
  ido-work-directory-list '("~/" "~/Desktop" "~/Documents" "~/src")
  ido-case-fold  t                 ; be case-insensitiver

  ido-enable-last-directory-history t ; remember last used dirs
  ido-max-work-directory-list 30   ; should be enough
  ido-max-work-file-list      50   ; remember many
  ido-use-filename-at-point nil    ; don't use filename at point (annoying)
  ido-use-url-at-point nil         ; don't use url at point (annoying)

  ido-enable-flex-matching nil     ; don't try to be too smart
  ido-max-prospects 8              ; don't spam my minibuffer
  ido-confirm-unique-completion t) ; wait for RET, even with unique completion

;; when using ido, the confirmation is rather annoying...
(setq confirm-nonexistent-file-or-buffer nil)

Answer 1

You can install a package which replaces the traditional completion interface, such as https://elpa.gnu.org/packages/counsel.html or https://elpa.gnu.org/packages/vertico.html.

Or indeed https://github.com/DarwinAwardWinner/ido-completing-read-plus, if you want to continue using the Ido interface.

When you enable such package, it can affect project-find-file as well.

Answer 2

Here is a way to use ido as completion framework almost everywhere:

(defvar ido-enable-replace-completing-read t
  "If t, use ido-completing-read instead of completing-read if possible.
    
    Set it to nil using let in around-advice for functions where the
    original completing-read is required.  For example, if a function
    foo absolutely must use the original completing-read, define some
    advice like this:
    
    (defadvice foo (around original-completing-read-only activate)
      (let (ido-enable-replace-completing-read) ad-do-it))")

;; Replace completing-read wherever possible, unless directed otherwise
(defadvice completing-read
    (around use-ido-when-possible activate)
  (if (or (not ido-enable-replace-completing-read) ; Manual override disable ido
          (and (boundp 'ido-cur-list)
               ido-cur-list)) ; Avoid infinite loop from ido calling this
      ad-do-it
    (let ((allcomp (all-completions "" collection predicate)))
      (if allcomp
          (setq ad-return-value
                (ido-completing-read prompt
                                     allcomp
                                     nil require-match initial-input hist def))
        ad-do-it))))

It surprises me that this requires so much plumbing. I'd expect ido to replace completion everywhere, as soon as (ido-mode 'both) runs.