Eli Zaretskii writes:

Hi Eli,

[.]

>> To reproduce, a
>> single character (that is not '.') and a newline suffices, typing
>> something like:
>> 
>>     PS1='0\n$ '
>> 
>> in an emacs shell and typing M-RET reproduces the problem.
>
> Can you suggest how to solve this?

Good question!  When I tried to add (message ...) debugging this
morning, it started (and kept) looping; so I had no idea how to proceed.
However, I tried again and got better results this time and have created
a patch that "works for me" (see attached).

The puzzle is that I don't know all the requirements, e.g., I have no
idea why the code was (blindly) using `last' to set `dsl' from the
shell-dirtrack-query's result, and only much later using
file-directory-p.

The code using `last' suggests to me that there could me more (partial?)
directory-like elements coming back from `shell-dirtrack-query' and that
in such a case, that I haven't oberved, the last must be the most
relevant?

Also, the nested while loops lateron with the concatenations suggest
that `shell-dirtrack-query' may not always return the needed directory
element as one string, but that it could be split up in parts that would
need to be concatenated?  Also, something that I didn't observe.

So, I've changed the code to prefer `seq-find' with `file-directory-p'
and reverse the list first, so that the last element remains the most
relevant.  Also, I've kept selecting the last element in case the
`seq-find' does not return a result.

Anyway, naively looking at my case only, it seems the code could be a
lot simpler, using just the `seq-find' and without the nested `while'
loops...so yeah, dunno ;)

Greetings,
Janneke