patch 8.2.3462: ModeChanged only uses one character for new_mode and old_mode

Problem:    The ModeChanged event only uses one character for the new_mode and
            old_mode values.
Solution:   Pass one as first argument to mode(). (issue #8856)

src/misc1.c

@@ -2657,7 +2657,7 @@ trigger_modechanged()
 #if defined(FEAT_EVAL) || defined(PROTO)
     dict_T	    *v_event;
     typval_T	    rettv;
-    typval_T	    tv;
+    typval_T	    tv[2];
     char_u	    *pat_pre;
     char_u	    *pat;
 
@@ -2666,8 +2666,10 @@ trigger_modechanged()
 
     v_event = get_vim_var_dict(VV_EVENT);
 
-    tv.v_type = VAR_UNKNOWN;
-    f_mode(&tv, &rettv);
+    tv[0].v_type = VAR_NUMBER;
+    tv[0].vval.v_number = 1;	    // get full mode
+    tv[1].v_type = VAR_UNKNOWN;
+    f_mode(tv, &rettv);
     (void)dict_add_string(v_event, "new_mode", rettv.vval.v_string);
     (void)dict_add_string(v_event, "old_mode", last_mode);
     dict_set_items_ro(v_event);

src/testdir/test_edit.vim

@@ -1918,7 +1918,7 @@ func Test_mode_changes()
   func! TestMode()
     call assert_equal(g:mode_seq[g:index], get(v:event, "old_mode"))
     call assert_equal(g:mode_seq[g:index + 1], get(v:event, "new_mode"))
-    call assert_equal(mode(), get(v:event, "new_mode"))
+    call assert_equal(mode(1), get(v:event, "new_mode"))
     let g:index += 1
   endfunc
 
@@ -1930,7 +1930,11 @@ func Test_mode_changes()
   au ModeChanged V:v :call DoIt()
   call feedkeys("Vv\<esc>", 'tnix')
   call assert_equal(4, g:count)
+  call assert_equal(len(g:mode_seq) - 1, g:index)
 
+  let g:index = 0
+  let g:mode_seq = ['n', 'i', 'niI', 'i', 'n']
+  call feedkeys("a\<C-O>l\<esc>", 'tnix')
   call assert_equal(len(g:mode_seq) - 1, g:index)
 
   au! ModeChanged

src/version.c

@@ -757,6 +757,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3462,
 /**/
     3461,
 /**/