It's amazing what writing a test will find.

(issue #16900)
 Reported by: bluecrow76


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@251677 65c4cc65-6c06-0410-ace0-fbb531ad65f3

funcs/func_strings.c

@@ -493,7 +493,7 @@ static int listfilter(struct ast_channel *chan, const char *cmd, char *parse, ch
 		ast_channel_lock(chan);
 	}
 	ast_str_substitute_variables(&orig_list, 0, chan, varsubst);
-	if (ast_str_strlen(orig_list)) {
+	if (!ast_str_strlen(orig_list)) {
 		ast_log(LOG_ERROR, "List variable '%s' not found\n", args.listname);
 		if (chan) {
 			ast_channel_unlock(chan);

tests/test_substitution.c

@@ -251,6 +251,8 @@ AST_TEST_DEFINE(test_substitution)
 	TEST(test_expected_result(test, c, "A${${baz}o:-1:1}A", "A3A"));
 	TEST(test_expected_result(test, c, "A${${baz}o:-2:1}A", "A2A"));
 	TEST(test_expected_result(test, c, "A${${baz}o:-2:-1}A", "A2A"));
+	pbx_builtin_setvar_helper(c, "list1", "ab&cd&ef");
+	TEST(test_expected_result(test, c, "${LISTFILTER(list1,&,cd)}", "ab&ef"));
 #undef TEST
 
 	/* For testing dialplan functions */