From 2d73ca67b844df6e1ed0319f5d454646d685caaa Mon Sep 17 00:00:00 2001
From: Jim Porter <jporterbugs@gmail.com>
Date: Tue, 1 Mar 2022 18:53:42 -0800
Subject: [PATCH 5/5] Allow splitting strings in Eshell expansions with "plain"
 strings

Since '$var[hello 0]' doesn't make sense when 'var' is a string, the
previous restriction was unnecessary.

* lisp/eshell/esh-var.el (Commentary): Update documentation.
(eshell-apply-indices): Allow "plain" strings to split strings.

* test/lisp/eshell/esh-var-test.el
(esh-var-test/interp-var-string-split-indices)
(esh-var-test/quoted-interp-var-string-split-indices): Update tests.

* doc/misc/eshell.texi (Dollars expansion): Update documentation.
---
 doc/misc/eshell.texi              |  6 +++---
 lisp/eshell/esh-var.el            | 17 +++++++----------
 test/lisp/eshell/esh-var-tests.el | 12 ++++++++++++
 3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/doc/misc/eshell.texi b/doc/misc/eshell.texi
index 3301a854eb..5581e5cd9e 100644
--- a/doc/misc/eshell.texi
+++ b/doc/misc/eshell.texi
@@ -1055,9 +1055,9 @@ Dollars Expansion
 
 @item $@var{expr}[@var{regexp} @var{i...}]
 As above (when @var{expr} expands to a string), but use @var{regexp}
-to split the string.  @var{regexp} can be any form other than a number
-or a plain variable name.  For example, @samp{$@var{var}[: 0]} will
-return the first element of a colon-delimited string.
+to split the string.  @var{regexp} can be any form other than a
+number.  For example, @samp{$@var{var}[: 0]} will return the first
+element of a colon-delimited string.
 
 @item $#@var{expr}
 Expands to the length of the result of @var{expr}, an expression in
diff --git a/lisp/eshell/esh-var.el b/lisp/eshell/esh-var.el
index 6f08a3fbc4..af89e35f55 100644
--- a/lisp/eshell/esh-var.el
+++ b/lisp/eshell/esh-var.el
@@ -74,9 +74,8 @@
 ;;   $EXPR["\\\\" 10]
 ;;
 ;; Separate on backslash characters.  Actually, the first argument --
-;; if it doesn't have the form of a number, or a plain variable name
-;; -- can be any regular expression.  So to split on numbers, use
-;; '$EXPR["[0-9]+" 10 20]'.
+;; if it doesn't have the form of a number -- can be any regular
+;; expression.  So to split on numbers, use '$EXPR["[0-9]+" 10 20]'.
 ;;
 ;;   $EXPR[hello]
 ;;
@@ -566,13 +565,11 @@ eshell-apply-indices
   (while indices
     (let ((refs (car indices)))
       (when (stringp value)
-	(let (separator)
-	  (if (not (or (not (stringp (caar indices)))
-		       (string-match
-			(concat "^" eshell-variable-name-regexp "$")
-			(caar indices))))
-	      (setq separator (caar indices)
-		    refs (cdr refs)))
+	(let (separator (index (caar indices)))
+          (when (and (stringp index)
+                     (not (get-text-property 0 'number index)))
+            (setq separator index
+                  refs (cdr refs)))
 	  (setq value
 		(mapcar #'eshell-convert
 			(split-string value separator)))))
diff --git a/test/lisp/eshell/esh-var-tests.el b/test/lisp/eshell/esh-var-tests.el
index e679174939..d09dd614de 100644
--- a/test/lisp/eshell/esh-var-tests.el
+++ b/test/lisp/eshell/esh-var-tests.el
@@ -84,6 +84,11 @@ esh-var-test/interp-var-string-split-indices
     (should (equal (eshell-test-command-result "echo $eshell-test-value[: 0]")
                    "zero"))
     (should (equal (eshell-test-command-result "echo $eshell-test-value[: 0 2]")
+                   '("zero" "two"))))
+  (let ((eshell-test-value "zeroXoneXtwoXthreeXfour"))
+    (should (equal (eshell-test-command-result "echo $eshell-test-value[X 0]")
+                   "zero"))
+    (should (equal (eshell-test-command-result "echo $eshell-test-value[X 0 2]")
                    '("zero" "two")))))
 
 (ert-deftest esh-var-test/interp-var-regexp-split-indices ()
@@ -216,6 +221,13 @@ esh-var-test/quoted-interp-var-string-split-indices
                    "zero"))
     (should (equal (eshell-test-command-result
                     "echo \"$eshell-test-value[: 0 2]\"")
+                   '("zero" "two"))))
+  (let ((eshell-test-value "zeroXoneXtwoXthreeXfour"))
+    (should (equal (eshell-test-command-result
+                    "echo \"$eshell-test-value[X 0]\"")
+                   "zero"))
+    (should (equal (eshell-test-command-result
+                    "echo \"$eshell-test-value[X 0 2]\"")
                    '("zero" "two")))))
 
 (ert-deftest esh-var-test/quoted-interp-var-regexp-split-indices ()
-- 
2.25.1