Re: emacs-30 f050b9c5033: Fix Tramp IPv6 handling in tests

[Madhu <enometh@meer.net>]

* Michael Albinus <87cymmomol.fsf@gmx.de> :
Wrote on Mon, 05 Aug 2024 20:21:30 +0200:
> Michael Albinus <michael.albinus@gmx.de> writes:
>>>> +		   :result ,(substring-no-properties
>>>> +			     (file-remote-p "/sudo::/tmp/foo" 'user)))
>>>
>>> just a caveat that substring-no-properties can end up being called on
>>> nil here.  I agree it is unlikely, but I managed to trigger it with the
>>> `swiper' package, where an unconditional (require 'tramp) in the midst
>>> of code kept failing.
>>
>> In that case (file-remote-p returns nil) the whole block doesn't make
>> sense. How did they manage to manipulate Tramp this way? Setting
>> tramp-mode to nil? Manipulating file-name-handler-alist?

It wasn't them, it was me, or I suspect it was some async (delayed
loading/reloading) glitch but I'm not sure how it happened.  AFAIK i was
not using the hammer on file-name-handler-alist [1], all I did was set
tramp-completion-file-name-handler-alist to nil.

> I've added a sanity check. Pushed to the emacs-30 branch.
Thanks

[1] a decade ago I used to disable tramp with this hammer, but it too
was ineffective when tramp got (somehow) reloaded so I abandoned it. I'm
pretty sure I had not manipulated this explicitly to trigger this crash.

```
(setq file-name-handler-alist
      (loop for x in file-name-handler-alist
	    for (pattern . symbol) = x
	    for name = (symbol-name symbol)
	    unless (string-match "tramp" name) collect x))
```