patch 8.2.3335: Vim9: not enough tests run with Vim9

Problem:    Vim9: not enough tests run with Vim9.
Solution:   Run a few more tests in Vim9 script and :def function.  Fix that
            items(), keys() and values9) return zero for a NULL dict.
            Make join() return an empty string for a NULL list.  Make sort()
            return an empty list for a NULL list.

Author: brammool

src/dict.c

@@ -1209,11 +1209,12 @@ dict_list(typval_T *argvars, typval_T *rettv, int what)
 	emsg(_(e_dictreq));
 	return;
     }
-    if ((d = argvars[0].vval.v_dict) == NULL)
-	return;
 
     if (rettv_list_alloc(rettv) == FAIL)
 	return;
+    if ((d = argvars[0].vval.v_dict) == NULL)
+	// empty dict behaves like an empty dict
+	return;
 
     todo = (int)d->dv_hashtab.ht_used;
     for (hi = d->dv_hashtab.ht_array; todo > 0; ++hi)

src/list.c

@@ -1436,15 +1436,15 @@ f_join(typval_T *argvars, typval_T *rettv)
 	emsg(_(e_listreq));
 	return;
     }
+    rettv->v_type = VAR_STRING;
     if (argvars[0].vval.v_list == NULL)
 	return;
+
     if (argvars[1].v_type == VAR_UNKNOWN)
 	sep = (char_u *)" ";
     else
 	sep = tv_get_string_chk(&argvars[1]);
 
-    rettv->v_type = VAR_STRING;
-
     if (sep != NULL)
     {
 	ga_init2(&ga, (int)sizeof(char), 80);
@@ -1968,11 +1968,13 @@ do_sort_uniq(typval_T *argvars, typval_T *rettv, int sort)
     else
     {
 	l = argvars[0].vval.v_list;
-	if (l == NULL || value_check_lock(l->lv_lock,
+	if (l != NULL && value_check_lock(l->lv_lock,
 	     (char_u *)(sort ? N_("sort() argument") : N_("uniq() argument")),
 									TRUE))
 	    goto theend;
 	rettv_list_set(rettv, l);
+	if (l == NULL)
+	    goto theend;
 	CHECK_LIST_MATERIALIZE(l);
 
 	len = list_len(l);
@@ -3110,32 +3112,35 @@ f_reverse(typval_T *argvars, typval_T *rettv)
 
     if (argvars[0].v_type != VAR_LIST)
 	semsg(_(e_listblobarg), "reverse()");
-    else if ((l = argvars[0].vval.v_list) != NULL
+    else
+    {
+	l = argvars[0].vval.v_list;
+	rettv_list_set(rettv, l);
+	if (l != NULL
 	    && !value_check_lock(l->lv_lock,
 				    (char_u *)N_("reverse() argument"), TRUE))
-    {
-	if (l->lv_first == &range_list_item)
 	{
-	    varnumber_T new_start = l->lv_u.nonmat.lv_start
+	    if (l->lv_first == &range_list_item)
+	    {
+		varnumber_T new_start = l->lv_u.nonmat.lv_start
 				  + (l->lv_len - 1) * l->lv_u.nonmat.lv_stride;
-	    l->lv_u.nonmat.lv_end = new_start
+		l->lv_u.nonmat.lv_end = new_start
 			   - (l->lv_u.nonmat.lv_end - l->lv_u.nonmat.lv_start);
-	    l->lv_u.nonmat.lv_start = new_start;
-	    l->lv_u.nonmat.lv_stride = -l->lv_u.nonmat.lv_stride;
-	    rettv_list_set(rettv, l);
-	    return;
-	}
-	li = l->lv_u.mat.lv_last;
-	l->lv_first = l->lv_u.mat.lv_last = NULL;
-	l->lv_len = 0;
-	while (li != NULL)
-	{
-	    ni = li->li_prev;
-	    list_append(l, li);
-	    li = ni;
+		l->lv_u.nonmat.lv_start = new_start;
+		l->lv_u.nonmat.lv_stride = -l->lv_u.nonmat.lv_stride;
+		return;
+	    }
+	    li = l->lv_u.mat.lv_last;
+	    l->lv_first = l->lv_u.mat.lv_last = NULL;
+	    l->lv_len = 0;
+	    while (li != NULL)
+	    {
+		ni = li->li_prev;
+		list_append(l, li);
+		li = ni;
+	    }
+	    l->lv_u.mat.lv_idx = l->lv_len - l->lv_u.mat.lv_idx - 1;
 	}
-	rettv_list_set(rettv, l);
-	l->lv_u.mat.lv_idx = l->lv_len - l->lv_u.mat.lv_idx - 1;
     }
 }