vim-patch:8.2.3993: when recording a change in Select mode char appears twice

Problem:    When recording a change in Select mode the first typed character
            appears twice.
Solution:   When putting the character back into typeahead remove it from
            recorded characters. (closes vim/vim#9462)
c88e977862

src/nvim/getchar.c

@@ -284,9 +284,19 @@ static void add_buff(buffheader_T *const buf, const char *const s, ptrdiff_t sle
   }
 }
 
-/*
- * Add number "n" to buffer "buf".
- */
+/// Delete "slen" bytes from the end of "buf".
+/// Only works when it was just added.
+static void delete_buff_tail(buffheader_T *buf, int slen)
+{
+  int len = (int)STRLEN(buf->bh_curr->b_str);
+
+  if (len >= slen) {
+    buf->bh_curr->b_str[len - slen] = NUL;
+    buf->bh_space += (size_t)slen;
+  }
+}
+
+/// Add number "n" to buffer "buf".
 static void add_num_buff(buffheader_T *buf, long n)
 {
   char number[32];
@@ -967,31 +977,31 @@ int ins_typebuf(char_u *str, int noremap, int offset, bool nottyped, bool silent
   return OK;
 }
 
-/*
- * Put character "c" back into the typeahead buffer.
- * Can be used for a character obtained by vgetc() that needs to be put back.
- * Uses cmd_silent, KeyTyped and KeyNoremap to restore the flags belonging to
- * the char.
- */
-void ins_char_typebuf(int c, int modifier)
+/// Put character "c" back into the typeahead buffer.
+/// Can be used for a character obtained by vgetc() that needs to be put back.
+/// Uses cmd_silent, KeyTyped and KeyNoremap to restore the flags belonging to
+/// the char.
+/// @return the length of what was inserted
+int ins_char_typebuf(int c, int modifier)
 {
   char_u buf[MB_MAXBYTES + 4];
-  int idx = 0;
+  int len = 0;
   if (modifier != 0) {
     buf[0] = K_SPECIAL;
     buf[1] = KS_MODIFIER;
     buf[2] = (char_u)modifier;
     buf[3] = NUL;
-    idx = 3;
+    len = 3;
   }
   if (IS_SPECIAL(c)) {
-    buf[idx] = K_SPECIAL;
-    buf[idx + 1] = (char_u)K_SECOND(c);
-    buf[idx + 2] = (char_u)K_THIRD(c);
-    buf[idx + 3] = NUL;
+    buf[len] = K_SPECIAL;
+    buf[len + 1] = (char_u)K_SECOND(c);
+    buf[len + 2] = (char_u)K_THIRD(c);
+    buf[len + 3] = NUL;
   } else {
-    char_u *p = buf + idx;
+    char_u *p = buf + len;
     int char_len = utf_char2bytes(c, p);
+    len += char_len;
     // If the character contains K_SPECIAL bytes they need escaping.
     for (int i = char_len; --i >= 0; p++) {
       if ((uint8_t)(*p) == K_SPECIAL) {
@@ -999,11 +1009,13 @@ void ins_char_typebuf(int c, int modifier)
         *p++ = K_SPECIAL;
         *p++ = KS_SPECIAL;
         *p = KE_FILLER;
+        len += 2;
       }
     }
     *p = NUL;
   }
   (void)ins_typebuf(buf, KeyNoremap, 0, !KeyTyped, cmd_silent);
+  return len;
 }
 
 /// Return TRUE if the typeahead buffer was changed (while waiting for a
@@ -1163,6 +1175,18 @@ static void gotchars(const char_u *chars, size_t len)
   maptick++;
 }
 
+/// Undo the last gotchars() for "len" bytes.  To be used when putting a typed
+/// character back into the typeahead buffer, thus gotchars() will be called
+/// again.
+/// Only affects recorded characters.
+void ungetchars(int len)
+{
+  if (reg_recording != 0) {
+    delete_buff_tail(&recordbuff, len);
+    last_recorded_len -= (size_t)len;
+  }
+}
+
 /*
  * Sync undo.  Called when typed characters are obtained from the typeahead
  * buffer, or when a menu is used.

src/nvim/normal.c

@@ -1010,7 +1010,12 @@ static int normal_execute(VimState *state, int key)
     // restart automatically.
     // Insert the typed character in the typeahead buffer, so that it can
     // be mapped in Insert mode.  Required for ":lmap" to work.
-    ins_char_typebuf(s->c, mod_mask);
+    int len = ins_char_typebuf(s->c, mod_mask);
+
+    // When recording the character will be recorded again, remove the
+    // previously recording.
+    ungetchars(len);
+
     if (restart_edit != 0) {
       s->c = 'd';
     } else {

src/nvim/testdir/test_registers.vim

@@ -121,6 +121,17 @@ func Test_recording_esc_sequence()
   endif
 endfunc
 
+func Test_recording_with_select_mode()
+  new
+  call feedkeys("qacc12345\<Esc>gH98765\<Esc>q", "tx")
+  call assert_equal("98765", getline(1))
+  call assert_equal("cc12345\<Esc>gH98765\<Esc>", @a)
+  call setline(1, 'asdf')
+  normal! @a
+  call assert_equal("98765", getline(1))
+  bwipe!
+endfunc
+
 " Test for executing the last used register (@)
 func Test_last_used_exec_reg()
   " Test for the @: command