Fix input of sharp-quoted symbols in Eshell with em-extpipe

* lisp/eshell/em-extpipe.el (eshell-parse-external-pipeline): Fix
misinterpreting sharp-quoted symbols as the beginning of single-quoted
strings (Bug#53518).  Add protection against a possible infinite loop.
* test/lisp/eshell/em-extpipe-tests.el (em-extpipe-test-17): New
test (bug#53518).

1 files changed, 4 insertions, 0 deletions

diff --git a/test/lisp/eshell/em-extpipe-tests.el b/test/lisp/eshell/em-extpipe-tests.el
index 1283b6b361f..0879ad5b0ca 100644
--- a/test/lisp/eshell/em-extpipe-tests.el
+++ b/test/lisp/eshell/em-extpipe-tests.el
@@ -202,4 +202,8 @@
       (eshell-command-result-p input "rab")
       (eshell-command-result-p "echo \"bar\" | rev" "nonsense"))))
 
+;; Confirm we don't break input of sharp-quoted symbols (Bug#53518).
+(em-extpipe-tests--deftest em-extpipe-test-17 "funcall #'upcase foo"
+  (eshell-command-result-p input "FOO"))
+
 ;;; em-extpipe-tests.el ends here