Dmitry Gutov <dmitry@gutov.dev> writes:
> I'm pushed the first of your patches, but the second needed some
> adjustments. Chiefly because we need to make sure it works with any
> value of project-read-file-name-function, so the impl can't be
> concentrated in just one of them.
>
> Check out the amended patch below. Any suggestions on how to do it
> more elegantly (without duplicating the add-to-history call) are
> welcome too.
>
> diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
> index e1d14474323..d810d8d9605 100644
> --- a/lisp/progmodes/project.el
> +++ b/lisp/progmodes/project.el
> @@ -1046,6 +1046,13 @@ project-read-file-name-function
>    :group 'project
>    :version "27.1")
>
> +(defun project--expand-file-name (filename project)
> +  (when-let ((old-root (get-text-property 0 'project filename)))
> +    (abbreviate-file-name
> +     (expand-file-name
> +      (file-relative-name filename old-root)
> +      (project-root project)))))
> +
>  (defun project--read-file-cpd-relative (prompt
>                                          all-files &optional predicate
>                                          hist mb-default)
> @@ -1124,9 +1131,18 @@ project-find-file-in
>                 dirs)
>              (project-files project dirs)))
>           (completion-ignore-case read-file-name-completion-ignore-case)
> -         (file (funcall project-read-file-name-function
> -                        "Find file" all-files nil 'file-name-history
> -                        suggested-filename)))
> +         (file
> +          (let ((file-name-history (mapcar
> +                                    (lambda (f)
> +                                      (or (project--expand-file-name
> f project) f))
> +                                    file-name-history)))
> +            (funcall project-read-file-name-function
> +                     "Find file" all-files nil 'file-name-history
> +                     suggested-filename))))
> +    (when history-add-new-input
> +      ;; Have to re-add it here because of the let-binding above.
> +      (add-to-history 'file-name-history
> +                      (propertize file 'project (project-root project))))
>      (if (string= file "")
>          (user-error "You didn't specify the file")
>        (find-file file))))

This seems good, sure.  But doesn't this make the history entries appear
twice?

Maybe we should just pull the history-adding functionality out of
project-read-file-name-function entirely.  I've tried doing that below.

Also, I realized just now that this should probably affect
project-find-dir as well, as should my previous patch adding
project-relative future history.  (I actually coincidentally just now
got a user request for "switch between projects and stay in the same
dir")

So here's a revised version of this history change which also affects
project-find-dir.  In a subsequent mail I'll send a patch for the
"future history" behavior of project-find-dir too.  (yet to be written)