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

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Jim Porter <jporterbugs <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 30.0.50; [PATCH] Indices in Eshell variable interpolation don't work
 with async subcommands
Date: Wed, 18 Jan 2023 19:36:41 -0800

[Message part 1 (text/plain, inline)]

Starting from "emacs -Q -f eshell":

  ~ $ echo $exec-path[0]
  /usr/local/sbin
  ~ $ echo $exec-path[${echo 0}]
  /usr/local/sbin
  ~ $ echo $exec-path[${*echo 0}]
  ;; no output

This is because 'eshell-eval-indices' gets an S-expr describing code to 
evaluate for the indices, and it just passes that to 'eval'. That's not 
the right way to do things for Eshell: instead, we should rely on 
'eshell-do-eval', which properly handles asynchronous evaluation. That's 
required for working with external commands like "*echo" (which calls 
the real /bin/echo).

The attached patch fixes this by changing 'eshell-eval-indices' to 
'eshell-indices', which does some minimal transformations on the S-expr 
for the indices, and then uses it to build the final S-expr to pass to 
'eshell-do-eval'.

This could possibly go in Emacs 29, since it's a bugfix to add onto a 
previous bugfix (see commit 990f36fa10). However, I'd lean towards just 
merging to master; this is a fairly obscure issue, and we can't just fix 
*every* bug we find on the release branch, or the branch will never 
stabilize. If someone else thinks it's important enough to go on the 
release branch though, I won't argue.

[0001-Fix-evaluation-of-asynchronous-expansions-in-Eshell-.patch (text/plain, attachment)]

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