For example, '${echo -e "hi\nbye"}[1]' should expand to "bye".
* lisp/eshell/esh-var.el (eshell-parse-variable-ref): Support applying
indices to '${}', '$()', and '$<>' forms.
(Bug#54227)
* lisp/eshell/esh-var-tests.el (esh-var-test/interp-lisp-indices)
(esh-var-test/interp-cmd-indices)
(esh-var-test/interp-cmd-external-indices)
(esh-var-test/quoted-interp-lisp-indices)
(esh-var-test/quoted-interp-cmd-indices): New tests.
Since '$var[hello 0]' doesn't make sense when 'var' is a string, the
previous restriction was unnecessary.
* lisp/eshell/esh-var.el (Commentary): Update documentation.
(eshell-apply-indices): Allow "plain" strings to split strings.
* test/lisp/eshell/esh-var-test.el
(esh-var-test/interp-var-string-split-indices)
(esh-var-test/quoted-interp-var-string-split-indices): Update tests.
* doc/misc/eshell.texi (Dollars expansion): Update documentation.
Previously, more-complex index expansions, like '$var[":" 0]' or
'$var[$(expr) 0]' failed to parse correctly.
* lisp/eshell/esh-var.el (Commentary): Clarify indexing and length
expansions.
(eshell-parse-indices): Expand docstring and support parsing inside
double-quotes.
(eshell-eval-indices): New function.
(eshell-parse-variable): Use it.
* test/lisp/eshell/esh-var-tests.el (eshell-test-value): New defvar.
(esh-var-test/interp-var-indices,
(esh-var-test/interp-var-split-indices)
(esh-var-test/interp-var-string-split-indices)
(esh-var-test/interp-var-regexp-split-indices)
(esh-var-test/interp-var-assoc, esh-var-test/interp-var-length-list)
(esh-var-test/interp-var-length-string)
(esh-var-test/interp-var-length-alist)
(esh-var-test/quoted-interp-var-indices)
(esh-var-test/quoted-interp-var-split-indices)
(esh-var-test/quoted-interp-var-string-split-indices)
(esh-var-test/quoted-interp-var-regexp-split-indices)
(esh-var-test/quoted-interp-var-assoc)
(esh-var-test/quoted-interp-var-length-list)
(esh-var-test/quoted-interp-var-length-string)
(esh-var-test/quoted-interp-var-length-alist): New tests.
* doc/misc/eshell.texi (Dollars Expansion): Expand and reword
documentation for indexing and length expansions.
For example,
echo "${echo hi}"
previously tried to run the program named 'echo hi', instead of 'echo'
with the argument 'hi'.
* lisp/eshell/esh-arg.el (eshell-parse-inner-double-quote):
New function.
* lisp/eshell/esh-var.el (eshell-parse-variable-ref): Support parsing
when wrapped in double-quiotes.
* test/lisp/eshell/esh-var-tests.el (esh-var-test/interp-var)
(esh-var-test/interp-quoted-var)
(esh-var-test/interp-quoted-var-concat)
(esh-var-test/quoted-interp-var)
(esh-var-test/quoted-interp-quoted-var)
(esh-var-test/quoted-interp-lisp, esh-var-test/quoted-interp-cmd)
(esh-var-test/quoted-interp-temp-cmd): New tests.
