bug#63539: 29.0.90; TRAMP fails to detect shell prompts containing ]

[Michael Albinus <michael.albinus@gmx.de>]

Spencer Baugh <sbaugh@janestreet.com> writes:

Hi Spencer,

>>> One can work around this by configuring the machine's prompt, but []
>>> seem relatively common in prompts (in my personal experience), and it
>>> would be nice if this worked by default.  (So far I've only seen [] in
>>> custom prompts but there are probably some OSs/distributions with [] in
>>> their prompt by default)
>>
>> What's wrong with the recipe for your remote .profile:
>>
>> [[ $TERM == "dumb" ]] && PS1='$ ' && return
>>
>> The Tramp manual gives an extended version of the recipe, which handles
>> also the zsh line editing problem, but you see the idea.
>
> [] seem relatively common in prompts (in my personal experience), and it
> would be nice if this worked by default.

"[whatever]" is covered in Tramp. What isn't covered is your use case
"[user@hostname] foo/bar/path $".

> Just as an additional point, I'm not always connecting to hosts that I
> can trivially change the .profile for.

That's why you can customize shell-prompt-pattern or tramp-shell-prompt-pattern.

>> And there is also the user option `tramp-shell-prompt-pattern' which you
>> can customize as you like.
>
> Yes, I'm setting this to remove the ] as a possible prompt character as
> a workaround.

It isn't a workaround. It is the (documented way.

>> Note, that Tramp cannot handle any case a user would prefer for
>> detecting the prompt.
>
> If it can cheaply handle more cases, why not?

Because there are further subtle problems. It isn't only about detecting
the prompt. It is also about avoiding false positives. Think about text
which is printed my motd. Or think about shell script fragments, which
could appear here and there prior the prompt, like

--8<---------------cut here---------------start------------->8---
if [ -n "$FOO" ]; then ...
--8<---------------cut here---------------end--------------->8---

Tramp shouldn't trap into this, and there were reports in the past
about. That's why I dislike to change the current state of affairs.

Best regards, Michael.