patch 9.1.1402: multi-byte mappings not properly stored in session file

Problem:  multi-byte mappings not properly stored in session file
Solution: unescape the mapping before writing out the mapping, prefer
          single-byte mapping name if possible (Miguel Barro)

closes: #17355

Signed-off-by: GuyBrush <miguel.barro@live.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/map.c

@@ -2180,7 +2180,18 @@ put_escstr(FILE *fd, char_u *strstart, int what)
 	    {
 		modifiers = str[2];
 		str += 3;
-		c = *str;
+
+		// Modifiers can be applied too to multi-byte characters.
+		p = mb_unescape(&str);
+
+		if (p == NULL)
+		    c = *str;
+		else
+		{
+		    // retrieve codepoint (character number) from unescaped string
+		    c = (*mb_ptr2char)(p);
+		    --str;
+		}
 	    }
 	    if (c == K_SPECIAL)
 	    {

src/misc2.c

@@ -1213,7 +1213,7 @@ handle_x_keys(int key)
 get_special_key_name(int c, int modifiers)
 {
     static char_u string[MAX_KEY_NAME_LEN + 1];
-    int	    i, idx;
+    int	    i, idx, len;
     int	    table_idx;
 
     string[0] = '<';
@@ -1286,10 +1286,11 @@ get_special_key_name(int c, int modifiers)
 	// Not a special key, only modifiers, output directly
 	else
 	{
-	    if (has_mbyte && (*mb_char2len)(c) > 1)
-		idx += (*mb_char2bytes)(c, string + idx);
-	    else if (vim_isprintc(c))
+	    len = (*mb_char2len)(c);
+	    if (len == 1 && vim_isprintc(c))
 		string[idx++] = c;
+	    else if (has_mbyte && len > 1)
+		idx += (*mb_char2bytes)(c, string + idx);
 	    else
 	    {
 		char_u	*s = transchar(c);

src/testdir/test_mksession_utf8.vim

@@ -102,4 +102,35 @@ func Test_mksession_utf8()
   set sessionoptions& splitbelow& fileencoding&
 endfunc
 
+func Test_session_multibyte_mappings()
+
+  " some characters readily available on european keyboards
+  let entries = [
+        \ ['n', '<M-ç>', '<M-ç>'],
+        \ ['n', '<M-º>', '<M-º>'],
+        \ ['n', '<M-¡>', '<M-¡>'],
+        \ ]
+  for entry in entries
+    exe entry[0] .. 'map ' .. entry[1] .. ' ' .. entry[2]
+  endfor
+
+  mkvimrc Xtestvimrc
+
+  nmapclear
+
+  for entry in entries
+    call assert_equal('', maparg(entry[1], entry[0]))
+  endfor
+
+  source Xtestvimrc
+
+  for entry in entries
+    call assert_equal(entry[2], maparg(entry[1], entry[0]))
+  endfor
+
+  nmapclear
+
+  call delete('Xtestvimrc')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -709,6 +709,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1402,
 /**/
     1401,
 /**/