* lisp/eshell: Make backslash a no-op in front of normal chars

Fixes: debbugs:8531

* lisp/eshell/esh-arg.el (eshell-parse-argument-hook): Update comment.
(eshell-parse-backslash): Return escaped character after backslash
if it is special.  Otherwise, if the backslash is not in a quoted
string, ignore the backslash and return the character after; if
the backslash is in a quoted string, return the backslash and the
character after.

* test/automated/eshell.el (eshell-test/escape-nonspecial)
(eshell-test/escape-nonspecial-unicode)
(eshell-test/escape-nonspecial-quoted)
(eshell-test/escape-special-quoted): Add tests for new
`eshell-parse-backslash' behavior.

1 files changed, 31 insertions, 0 deletions

diff --git a/test/automated/eshell.el b/test/automated/eshell.el
index d51355fe5ca..81898db79a7 100644
--- a/test/automated/eshell.el
+++ b/test/automated/eshell.el
@@ -166,6 +166,37 @@ e.g. \"{(+ 1 2)} 3\" => 3"
    (eshell-command-result-p "+ 1 2; + $_ 4"
                              "3\n6\n")))
 
+(ert-deftest eshell-test/escape-nonspecial ()
+  "Test that \"\\c\" and \"c\" are equivalent when \"c\" is not a
+special character."
+  (with-temp-eshell
+   (eshell-command-result-p "echo he\\llo"
+                            "hello\n")))
+
+(ert-deftest eshell-test/escape-nonspecial-unicode ()
+  "Test that \"\\c\" and \"c\" are equivalent when \"c\" is a
+unicode character (unicode characters are nonspecial by
+definition)."
+  (with-temp-eshell
+   (eshell-command-result-p "echo Vid\\éos"
+                            "Vidéos\n")))
+
+(ert-deftest eshell-test/escape-nonspecial-quoted ()
+  "Test that the backslash is preserved for escaped nonspecial
+chars"
+  (with-temp-eshell
+   (eshell-command-result-p "echo \"h\\i\""
+                            ;; Backslashes are doubled for regexp.
+                            "h\\\\i\n")))
+
+(ert-deftest eshell-test/escape-special-quoted ()
+  "Test that the backslash is not preserved for escaped special
+chars"
+  (with-temp-eshell
+   (eshell-command-result-p "echo \"h\\\\i\""
+                            ;; Backslashes are doubled for regexp.
+                            "h\\\\i\n")))
+
 (ert-deftest eshell-test/command-running-p ()
   "Modeline should show no command running"
   (with-temp-eshell