Thanks Michael, I finally use a new variable
helm--minibuffer-completing-file-name which doesn't affect
file-directory-p.

Michael Albinus <michael.albinus@gmx.de> writes:

> Thierry Volpiatto <thievol@posteo.net> writes:
>
>> Hi Michael,
>
> Hi Thierry,
>
>>>> In Emacs-30+:
>>>>
>>>> (let ((minibuffer-completing-file-name t)) (file-directory-p "/ssh"))
>>>> => t
>>>>
>>>> which is wrong obviously.
>>>
>>> No, it isn't. It is intended.
>>
>> Hmm, It is perhaps intended and I believe it fixes some problem, but it is
>> wrong anyway, "/ssh" is NOT a directory.
>
> Nobody says so. Remember, we're in file name completion, and Tramp must
> trigger some action from the completion machinery. A non-nil return of
> file-directory-p is such a trigger.
>
>> Can I use file-attributes instead or it is affected as well?
>
> Should work. Check tramp-completion-file-name-handler-alist. It cares
> only about
>
> --8<---------------cut here---------------start------------->8---
> ((expand-file-name . tramp-completion-handle-expand-file-name)
>  (file-directory-p . tramp-completion-handle-file-directory-p)
>  (file-exists-p . tramp-completion-handle-file-exists-p)
>  (file-name-all-completions . tramp-completion-handle-file-name-all-completions)
>  (file-name-completion . tramp-completion-handle-file-name-completion)
>  (file-name-directory . tramp-completion-handle-file-name-directory)
>  (file-name-nondirectory . tramp-completion-handle-file-name-nondirectory))
> --8<---------------cut here---------------end--------------->8---
>
> Alternatively, you could bind temporarily tramp-mode to nil. See
> tramp-completion-file-name-handler:
>
> --8<---------------cut here---------------start------------->8---
>   (if-let*
>       ((fn (and tramp-mode minibuffer-completing-file-name
> 		(assoc operation tramp-completion-file-name-handler-alist))))
>       (save-match-data (apply (cdr fn) args))
>     (tramp-run-real-handler operation args)))
> --8<---------------cut here---------------end--------------->8---
>
>> Thanks.
>
> Best regards, Michael.

-- 
Thierry