bug#60942: 30.0.50; [PATCH] Indices in Eshell variable interpolation don't work with async subcommands

[Jim Porter]

On 1/18/2023 10:49 PM, Eli Zaretskii wrote:
> Why do you remove a non-internal function?  We cannot possibly do that
> if this is going to be installed on the emacs-29 branch.  But even if
> you are going to install on master, why not leave that function alone?
> Some code somewhere could be using it, and we don't usually remove
> functions before a period of deprecation.

I can keep 'eshell-eval-indices' around and mark it obsolete if you 
prefer; it wouldn't hurt anything. I could also fix this bug in that 
function, though it would be an inferior fix compared to the new 
'eshell-indices' function, so we definitely want that new function (or 
something very similar). I'm not sure fixing 'eshell-eval-indices' is 
worth it though, since I'd be very surprised if anyone called that 
function directly.

For context, 'eshell-eval-indices' is a function I added in Emacs 29 to 
fix some related issues with indices[1], but at the time I didn't fully 
understand Eshell's internals and so implemented the fix incorrectly 
(though it works for most common cases). It probably could have been 
marked as internal at the time, but Eshell doesn't seem to do that 
regularly, even for functions that external code would be very unlikely 
to find useful.


[1] In particular, the second case in my original message fails even 
more severely in Emacs 28:

  ~/config $ echo $exec-path[${echo 0}]
  Wrong type argument: number-or-marker-p, (eshell-escape-arg (let 
((indices 'nil)) (eshell-convert (eshell-command-to-value 
(eshell-as-subcommand (eshell-trap-errors (eshell-named-command "echo" 
(list #("0" 0 1 (number t))))))))))