Re: [PATCH] `completing-read`: Add `group-function` support to completion metadata (REVISED PATCH VERSION 4)

[Juri Linkov]

>> I attached the current set of patches. The last patch
>> "0005-group-function-Implement-generalized-action-argument.patch"
>> implements the generalized action argument. The other patches (1-4) do
>> not differ from the previously sent patches. I send them for completeness.

Thanks, I tested it with mule--ucs-names-group, and everything works well.

> Correction to the lastest patch. The `minibuffer--group-by` function
> should actually be written as follows:
>
> (defun minibuffer--group-by (group-fun elems)
>   "Group ELEMS by GROUP-FUN."
>   (let ((groups))
>     (dolist (cand elems)
>       (let* ((key (funcall group-fun 'title cand))
>              (group (assoc key groups)))
>         (if group
>             (setcdr group (cons cand (cdr group)))
>           (push (list key cand) groups))))
>     ;; FIXME: Is thread-last allowed in minibuffer.el?

subr-x is not preloaded, but since thread-last is a macro maybe it's possible
to expand it during compilation: (eval-when-compile (require 'subr-x))

>     (setq groups (nreverse groups)
>           groups (mapc (lambda (x)
>                          (setcdr x (nreverse (cdr x))))
>                        groups)
>           groups (funcall group-fun 'sort groups)
>           groups (mapcar #'cdr groups))
>     (apply #'nconc groups)))

Or maybe simply `mapcan`.