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

[Jim Porter <jporterbugs@gmail.com>]

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On 1/18/2023 11:37 PM, Jim Porter wrote:
> 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.

Here's a patch that does this. It doesn't try to fix 
'eshell-eval-indices', since people shouldn't use that anyway. (I also 
renamed the new 'eshell-indices' to 'eshell-prepare-indices' to be clearer.)

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From 4cc14646a50b237d38cfb6643858cb379366141a Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Wed, 18 Jan 2023 19:15:38 -0800
Subject: [PATCH] Fix evaluation of asynchronous expansions in Eshell indices

Previously, this code passed the indices to a separate function, which
called 'eval' on them, but it should instead make an S-expr that
'eshell-do-eval' can evaluate.

* lisp/eshell/esh-var.el (eshell-eval-indices): Mark obsolete.
(eshell-prepare-indices): New function...
(eshell-parse-variable): ... use it.  Also, remove irrelevant comment.
(eshell-parse-variable-ref): Fix quoting in docstring.
(eshell-parse-indices): Fix typo in docstring.

* test/lisp/eshell/esh-var-tests.el
(esh-var-test/interp-var-indices-subcommand)
(esh-var-test/quoted-interp-var-indices-subcommand): New tests.
---
 lisp/eshell/esh-var.el            | 14 +++++++++-----
 test/lisp/eshell/esh-var-tests.el | 25 +++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/lisp/eshell/esh-var.el b/lisp/eshell/esh-var.el
index fd76a2c6f09..0998fc6b86a 100644
--- a/lisp/eshell/esh-var.el
+++ b/lisp/eshell/esh-var.el
@@ -467,9 +467,7 @@ eshell-parse-variable
 	  indices (and (not (eobp))
 		       (eq (char-after) ?\[)
 		       (eshell-parse-indices))
-          ;; This is an expression that will be evaluated by `eshell-do-eval',
-          ;; which only support let-binding of dynamically-scoped vars
-	  value `(let ((indices (eshell-eval-indices ',indices))) ,value))
+          value `(let ((indices ,(eshell-prepare-indices indices))) ,value))
     (when get-len
       (setq value `(length ,value)))
     (when eshell-current-quoted
@@ -496,7 +494,7 @@ eshell-parse-variable-ref
 
   NAME          an environment or Lisp variable value
   \"LONG-NAME\"   disambiguates the length of the name
-  `LONG-NAME'   as above
+  \\='LONG-NAME\\='   as above
   {COMMAND}     result of command is variable's value
   (LISP-FORM)   result of Lisp form is variable's value
   <COMMAND>     write the output of command to a temporary file;
@@ -591,7 +589,7 @@ eshell-parse-indices
   "Parse and return a list of index-lists.
 
 For example, \"[0 1][2]\" becomes:
-  ((\"0\" \"1\") (\"2\")."
+  ((\"0\" \"1\") (\"2\"))."
   (let (indices)
     (while (eq (char-after) ?\[)
       (let ((end (eshell-find-delimiter ?\[ ?\])))
@@ -609,8 +607,14 @@ eshell-parse-indices
 
 (defun eshell-eval-indices (indices)
   "Evaluate INDICES, a list of index-lists generated by `eshell-parse-indices'."
+  (declare (obsolete eshell-prepare-indices "30.1"))
   (mapcar (lambda (i) (mapcar #'eval i)) indices))
 
+(defun eshell-prepare-indices (indices)
+  "Prepare INDICES to be evaluated by Eshell.
+INDICES is a list of index-lists generated by `eshell-parse-indices'."
+  `(list ,@(mapcar (lambda (idx-list) (cons 'list idx-list)) indices)))
+
 (defun eshell-get-variable (name &optional indices quoted)
   "Get the value for the variable NAME.
 INDICES is a list of index-lists (see `eshell-parse-indices').
diff --git a/test/lisp/eshell/esh-var-tests.el b/test/lisp/eshell/esh-var-tests.el
index 0cc1b92266f..82324d72163 100644
--- a/test/lisp/eshell/esh-var-tests.el
+++ b/test/lisp/eshell/esh-var-tests.el
@@ -82,6 +82,17 @@ esh-var-test/interp-var-indices
     (eshell-command-result-equal "echo $eshell-test-value[0 2 4]"
                                  '("zero" "two" "four"))))
 
+(ert-deftest esh-var-test/interp-var-indices-subcommand ()
+  "Interpolate list variable with subcommand expansion for indices"
+  (skip-unless (executable-find "echo"))
+  (let ((eshell-test-value '("zero" "one" "two" "three" "four")))
+    (eshell-command-result-equal
+     "echo $eshell-test-value[${*echo 0}]"
+     "zero")
+    (eshell-command-result-equal
+     "echo $eshell-test-value[${*echo 0} ${*echo 2}]"
+     '("zero" "two"))))
+
 (ert-deftest esh-var-test/interp-var-split-indices ()
   "Interpolate string variable with indices"
   (let ((eshell-test-value "zero one two three four"))
@@ -271,6 +282,20 @@ esh-var-test/quoted-interp-var-indices
     (eshell-command-result-equal "echo \"$eshell-test-value[1 2 4]\""
                                  "(\"one\" \"two\" \"four\")")))
 
+(ert-deftest esh-var-test/quote-interp-var-indices-subcommand ()
+  "Interpolate list variable with subcommand expansion for indices
+inside double-quotes"
+  (skip-unless (executable-find "echo"))
+  (let ((eshell-test-value '("zero" "one" "two" "three" "four")))
+    (eshell-command-result-equal
+     "echo \"$eshell-test-value[${*echo 0}]\""
+     "zero")
+    ;; FIXME: These tests would use the 0th index like the other tests
+    ;; here, but see above.
+    (eshell-command-result-equal
+     "echo \"$eshell-test-value[${*echo 1} ${*echo 2}]\""
+     "(\"one\" \"two\")")))
+
 (ert-deftest esh-var-test/quoted-interp-var-split-indices ()
   "Interpolate string variable with indices inside double-quotes"
   (let ((eshell-test-value "zero one two three four"))
-- 
2.25.1