Handle escaped characters in Eshell special references (e.g. buffers)

* lisp/eshell/esh-arg.el (eshell-parse-special-reference): Unescape
escaped characters.

* test/lisp/eshell/eshell-tests-helpers.el (with-temp-eshell): Restore
current buffer after evaluating BODY.

* test/lisp/eshell/eshell-tests.el (eshell-test/redirect-buffer)
(eshell-test/redirect-buffer-escaped): New tests (bug#55204).

lisp/eshell/esh-arg.el

@@ -401,7 +401,9 @@ If the form has no `type', the syntax is parsed as if `type' were
         (if (eshell-arg-delimiter (1+ end))
             (prog1
                 (list (if buffer-p 'get-buffer-create 'get-process)
-                      (buffer-substring-no-properties (point) end))
+                      (replace-regexp-in-string
+                       (rx "\\" (group (or "\\" "<" ">"))) "\\1"
+                       (buffer-substring-no-properties (point) end)))
               (goto-char (1+ end)))
           (ignore (goto-char here)))))))
 

test/lisp/eshell/eshell-tests-helpers.el

@@ -38,17 +38,18 @@ See `eshell-wait-for-subprocess'.")
 
 (defmacro with-temp-eshell (&rest body)
   "Evaluate BODY in a temporary Eshell buffer."
-  `(ert-with-temp-directory eshell-directory-name
-     (let* (;; We want no history file, so prevent Eshell from falling
-            ;; back on $HISTFILE.
-            (process-environment (cons "HISTFILE" process-environment))
-            (eshell-history-file-name nil)
-            (eshell-buffer (eshell t)))
-       (unwind-protect
-           (with-current-buffer eshell-buffer
-             ,@body)
-         (let (kill-buffer-query-functions)
-           (kill-buffer eshell-buffer))))))
+  `(save-current-buffer
+     (ert-with-temp-directory eshell-directory-name
+       (let* (;; We want no history file, so prevent Eshell from falling
+              ;; back on $HISTFILE.
+              (process-environment (cons "HISTFILE" process-environment))
+              (eshell-history-file-name nil)
+              (eshell-buffer (eshell t)))
+         (unwind-protect
+             (with-current-buffer eshell-buffer
+               ,@body)
+           (let (kill-buffer-query-functions)
+             (kill-buffer eshell-buffer)))))))
 
 (defun eshell-wait-for-subprocess (&optional all)
   "Wait until there is no interactive subprocess running in Eshell.

test/lisp/eshell/eshell-tests.el

@@ -114,6 +114,25 @@ e.g. \"{(+ 1 2)} 3\" => 3"
    (eshell-wait-for-subprocess)
    (eshell-match-result "OLLEH\n")))
 
+(ert-deftest eshell-test/redirect-buffer ()
+  "Check that piping to a buffer works"
+  (with-temp-buffer
+    (rename-buffer "eshell-temp-buffer" t)
+    (let ((bufname (buffer-name)))
+      (with-temp-eshell
+       (eshell-insert-command (format "echo hi > #<%s>" bufname)))
+      (should (equal (buffer-string) "hi")))))
+
+(ert-deftest eshell-test/redirect-buffer-escaped ()
+  "Check that piping to a buffer with escaped characters works"
+  (with-temp-buffer
+    (rename-buffer "eshell\\temp\\buffer" t)
+    (let ((bufname (buffer-name)))
+      (with-temp-eshell
+       (eshell-insert-command (format "echo hi > #<%s>"
+                                      (string-replace "\\" "\\\\" bufname))))
+      (should (equal (buffer-string) "hi")))))
+
 (ert-deftest eshell-test/inside-emacs-var ()
   "Test presence of \"INSIDE_EMACS\" in subprocesses"
   (with-temp-eshell