patch 9.0.0331: cannot use items() on a string

Problem:    Cannot use items() on a string.
Solution:   Make items() work on a string. (closes #11016)

src/dict.c

@@ -1456,7 +1456,6 @@ dict2list(typval_T *argvars, typval_T *rettv, dict2list_T what)
     dictitem_T	*di;
     hashitem_T	*hi;
     listitem_T	*li;
-    listitem_T	*li2;
     dict_T	*d;
     int		todo;
 
@@ -1464,7 +1463,7 @@ dict2list(typval_T *argvars, typval_T *rettv, dict2list_T what)
 	return;
 
     if ((what == DICT2LIST_ITEMS
-		? check_for_list_or_dict_arg(argvars, 0)
+		? check_for_string_or_list_or_dict_arg(argvars, 0)
 		: check_for_dict_arg(argvars, 0)) == FAIL)
 	return;
 
@@ -1509,19 +1508,9 @@ dict2list(typval_T *argvars, typval_T *rettv, dict2list_T what)
 		    break;
 		++l2->lv_refcount;
 
-		li2 = listitem_alloc();
+		if (list_append_string(l2, di->di_key, -1) == FAIL
-		if (li2 == NULL)
+			|| list_append_tv(l2, &di->di_tv) == FAIL)
 		    break;
-		list_append(l2, li2);
-		li2->li_tv.v_type = VAR_STRING;
-		li2->li_tv.v_lock = 0;
-		li2->li_tv.vval.v_string = vim_strsave(di->di_key);
-
-		li2 = listitem_alloc();
-		if (li2 == NULL)
-		    break;
-		list_append(l2, li2);
-		copy_tv(&di->di_tv, &li2->li_tv);
 	    }
 	}
     }
@@ -1533,7 +1522,9 @@ dict2list(typval_T *argvars, typval_T *rettv, dict2list_T what)
     void
 f_items(typval_T *argvars, typval_T *rettv)
 {
-    if (argvars[0].v_type == VAR_LIST)
+    if (argvars[0].v_type == VAR_STRING)
+	string2items(argvars, rettv);
+    else if (argvars[0].v_type == VAR_LIST)
 	list2items(argvars, rettv);
     else
 	dict2list(argvars, rettv, DICT2LIST_ITEMS);

src/evalfunc.c

@@ -902,7 +902,7 @@ arg_slice1(type_T *type, type_T *decl_type UNUSED, argcontext_T *context)
  * or any)
  */
     static int
-arg_count1(type_T *type, type_T *decl_type UNUSED, argcontext_T *context)
+arg_string_or_list_or_dict(type_T *type, type_T *decl_type UNUSED, argcontext_T *context)
 {
     if (type->tt_type == VAR_ANY
 	    || type->tt_type == VAR_UNKNOWN
@@ -911,7 +911,8 @@ arg_count1(type_T *type, type_T *decl_type UNUSED, argcontext_T *context)
 	    || type->tt_type == VAR_DICT)
 	return OK;
 
-    arg_type_mismatch(&t_string, type, context->arg_idx + 1);
+    semsg(_(e_string_list_or_dict_required_for_argument_nr),
+							 context->arg_idx + 1);
     return FAIL;
 }
 
@@ -950,6 +951,7 @@ static argcheck_T arg1_list_number[] = {arg_list_number};
 static argcheck_T arg1_list_or_blob[] = {arg_list_or_blob};
 static argcheck_T arg1_list_or_dict[] = {arg_list_or_dict};
 static argcheck_T arg1_list_string[] = {arg_list_string};
+static argcheck_T arg1_string_or_list_or_dict[] = {arg_string_or_list_or_dict};
 static argcheck_T arg1_lnum[] = {arg_lnum};
 static argcheck_T arg1_number[] = {arg_number};
 static argcheck_T arg1_string[] = {arg_string};
@@ -1028,7 +1030,7 @@ static argcheck_T arg34_assert_inrange[] = {arg_float_or_nr, arg_float_or_nr, ar
 static argcheck_T arg4_browse[] = {arg_bool, arg_string, arg_string, arg_string};
 static argcheck_T arg23_chanexpr[] = {arg_chan_or_job, NULL, arg_dict_any};
 static argcheck_T arg23_chanraw[] = {arg_chan_or_job, arg_string_or_blob, arg_dict_any};
-static argcheck_T arg24_count[] = {arg_count1, NULL, arg_bool, arg_number};
+static argcheck_T arg24_count[] = {arg_string_or_list_or_dict, NULL, arg_bool, arg_number};
 static argcheck_T arg13_cursor[] = {arg_cursor1, arg_number, arg_number};
 static argcheck_T arg12_deepcopy[] = {NULL, arg_bool};
 static argcheck_T arg12_execute[] = {arg_string_or_list_string, arg_string};
@@ -2029,7 +2031,7 @@ static funcentry_T global_functions[] =
 			ret_number_bool,    f_islocked},
     {"isnan",		1, 1, FEARG_1,	    arg1_float_or_nr,
 			ret_number_bool,    MATH_FUNC(f_isnan)},
-    {"items",		1, 1, FEARG_1,	    arg1_list_or_dict,
+    {"items",		1, 1, FEARG_1,	    arg1_string_or_list_or_dict,
 			ret_list_items,	    f_items},
     {"job_getchannel",	1, 1, FEARG_1,	    arg1_job,
 			ret_channel,	    JOB_FUNC(f_job_getchannel)},

src/list.c

@@ -1065,9 +1065,8 @@ list2items(typval_T *argvars, typval_T *rettv)
 
     if (rettv_list_alloc(rettv) == FAIL)
 	return;
-
     if (l == NULL)
-	return;  // empty list behaves like an empty list
+	return;  // null list behaves like an empty list
 
     // TODO: would be more efficient to not materialize the argument
     CHECK_LIST_MATERIALIZE(l);
@@ -1084,6 +1083,39 @@ list2items(typval_T *argvars, typval_T *rettv)
     }
 }
 
+/*
+ * "items(string)" function
+ * Caller must have already checked that argvars[0] is a String.
+ */
+    void
+string2items(typval_T *argvars, typval_T *rettv)
+{
+    char_u	*p = argvars[0].vval.v_string;
+    varnumber_T idx;
+
+    if (rettv_list_alloc(rettv) == FAIL)
+	return;
+    if (p == NULL)
+	return;  // null string behaves like an empty string
+
+    for (idx = 0; *p != NUL; ++idx)
+    {
+	int	    len = mb_ptr2len(p);
+	list_T	    *l2;
+
+	if (len == 0)
+	    break;
+	l2 = list_alloc();
+	if (l2 == NULL)
+	    break;
+	if (list_append_list(rettv->vval.v_list, l2) == FAIL
+		|| list_append_number(l2, idx) == FAIL
+		|| list_append_string(l2, p, len) == FAIL)
+	    break;
+	p += len;
+    }
+}
+
 /*
  * Extend "l1" with "l2".  "l1" must not be NULL.
  * If "bef" is NULL append at the end, otherwise insert before this item.

src/proto/list.pro

@@ -36,6 +36,7 @@ int list_assign_range(list_T *dest, list_T *src, long idx1_arg, long idx2, int e
 void f_flatten(typval_T *argvars, typval_T *rettv);
 void f_flattennew(typval_T *argvars, typval_T *rettv);
 void list2items(typval_T *argvars, typval_T *rettv);
+void string2items(typval_T *argvars, typval_T *rettv);
 int list_extend(list_T *l1, list_T *l2, listitem_T *bef);
 int list_concat(list_T *l1, list_T *l2, typval_T *tv);
 list_T *list_slice(list_T *ol, long n1, long n2);

src/testdir/test_listdict.vim

@@ -206,7 +206,16 @@ func Test_list_items()
   endfor
   call assert_equal([[0, 'a'], [1, 'b'], [2, 'c']], r)
 
-  call assert_fails('call items(3)', 'E1227:')
+  call assert_fails('call items(3)', 'E1225:')
+endfunc
+
+func Test_string_items()
+  let r = []
+  let s = 'ábツ'
+  for [idx, val] in items(s)
+    call extend(r, [[idx, val]])
+  endfor
+  call assert_equal([[0, 'á'], [1, 'b'], [2, 'ツ']], r)
 endfunc
 
 " Test removing items in list

src/testdir/test_vim9_builtin.vim

@@ -799,7 +799,7 @@ enddef
 def Test_count()
   count('ABC ABC ABC', 'b', true)->assert_equal(3)
   count('ABC ABC ABC', 'b', false)->assert_equal(0)
-  v9.CheckDefAndScriptFailure(['count(10, 1)'], ['E1013: Argument 1: type mismatch, expected string but got number', 'E1225: String, List or Dictionary required for argument 1'])
+  v9.CheckDefAndScriptFailure(['count(10, 1)'], 'E1225: String, List or Dictionary required for argument 1')
   v9.CheckDefAndScriptFailure(['count("a", [1], 2)'], ['E1013: Argument 3: type mismatch, expected bool but got number', 'E1212: Bool required for argument 3'])
   v9.CheckDefAndScriptFailure(['count("a", [1], 0, "b")'], ['E1013: Argument 4: type mismatch, expected number but got string', 'E1210: Number required for argument 4'])
   count([1, 2, 2, 3], 2)->assert_equal(2)
@@ -2244,7 +2244,7 @@ def Test_islocked()
 enddef
 
 def Test_items()
-  v9.CheckDefFailure(['"x"->items()'], 'E1013: Argument 1: type mismatch, expected list<any> but got string')
+  v9.CheckDefFailure(['123->items()'], 'E1225:')
   assert_equal([['a', 10], ['b', 20]], {'a': 10, 'b': 20}->items())
   assert_equal([], {}->items())
   assert_equal(['x', 'x'], {'a': 10, 'b': 20}->items()->map((_, _) => 'x'))
@@ -2252,6 +2252,10 @@ def Test_items()
   assert_equal([[0, 'a'], [1, 'b']], ['a', 'b']->items())
   assert_equal([], []->items())
   assert_equal([], test_null_list()->items())
+
+  assert_equal([[0, 'a'], [1, '웃'], [2, 'ć']], 'a웃ć'->items())
+  assert_equal([], ''->items())
+  assert_equal([], test_null_string()->items())
 enddef
 
 def Test_job_getchannel()

src/version.c

@@ -707,6 +707,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    331,
 /**/
     330,
 /**/