vim-patch:8.2.2819: finishing an abbreviation with multi-byte char may not work

Problem:    Finishing an abbreviation with a multi-byte char may not work.
Solution:   Escape K_SPECIAL in the typed character. (closes vim/vim#8160)
4934ed34c3

src/nvim/getchar.c

@@ -3831,7 +3831,16 @@ bool check_abbr(int c, char_u *ptr, int col, int mincol)
           if (c >= ABBR_OFF) {
             c -= ABBR_OFF;
           }
-          j += utf_char2bytes(c, tb + j);
+          int newlen = utf_char2bytes(c, tb + j);
+          tb[j + newlen] = NUL;
+          // Need to escape K_SPECIAL.
+          char_u *escaped = vim_strsave_escape_csi(tb + j);
+          if (escaped != NULL) {
+            newlen = (int)STRLEN(escaped);
+            memmove(tb + j, escaped, (size_t)newlen);
+            j += newlen;
+            xfree(escaped);
+          }
         }
         tb[j] = NUL;
         // insert the last typed char

src/nvim/testdir/test_mapping.vim

@@ -559,4 +559,13 @@ func Test_map_cmdkey_redo()
   ounmap i-
 endfunc
 
+func Test_abbreviate_multi_byte()
+  new
+  iabbrev foo bar
+  call feedkeys("ifoo…\<Esc>", 'xt')
+  call assert_equal("bar…", getline(1))
+  iunabbrev foo
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab