Subject: bug#79173: 30.1; TRAMP simplified syntax produces empty completing-read candidates

From: Michael Albinus <[email-masked]>
Date: Tue, 05 Aug 2025 10:14:00 +0200

Reuben Thomas via "Bug reports for GNU Emacs, the Swiss army knife of
text editors" <[email-masked]> writes:

Hi Reuben,

> I’m a bit unsure how to demonstrate this bug in vanilla Emacs. See
> https://github.com/minad/vertico/discussions/623 for the original
> context in which I found this problem, using the vertico package. The
> author assures me this is an Emacs bug, and gives his reasoning there.

Thanks for the bug report. Yes, I could reproduce the problem according
to your recipe with Emacs 30. I'm using a recent build from the emacs-30
branch:

--8<---------------cut here---------------start------------->8---
GNU Emacs 31.0.50 (build 13, x86_64-pc-linux-gnu, GTK+ Version
 3.24.49, cairo version 1.18.2) of 2025-07-22
--8<---------------cut here---------------end--------------->8---

> Also, according to him it is possible that it has already been fixed on
> master.

I've modified your recipe slightly in my next test. In package-isolate,
I've said vertico-2.4,tramp-2.8.0.1 :

--8<---------------cut here---------------start------------->8---
;; - compat-30.1.0.0 (dependency)
;; - seq-2.24 (dependency)
;; - tramp-2.8.0.1
;; - vertico-2.4
--8<---------------cut here---------------end--------------->8---

Tramp 2.8 is the version in Emacs' master branch. The same problem
appeared.

Now a third test, like the first one but using Emacs 31 from the master
branch. No error happens.

Conclusion: the problem is fixed im Emacs' master branch. Unfortunately,
this fix is not in Tramp itself, so it doesn't suffices to use a recent
Tramp version from ELPA.

So I propose to close your bug. This is unfortune for people using Emacs
30, but I don't know what and how to backport.

Best regards, Michael.