From b622dca9158d1ff870ff71ad89f44d7a655b02ce Mon Sep 17 00:00:00 2001
From: katekyy <74244551+katekyy@users.noreply.github.com>
Date: Sat, 29 Jul 2023 23:12:51 +0200
Subject: [PATCH] builtin: fix split_nth() and rsplit_nth() on an empty
 delimeter (#19005)

---
 vlib/builtin/string.v      | 4 ++--
 vlib/builtin/string_test.v | 9 +++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 02ae63bda3..02c67c4788 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -865,7 +865,7 @@ pub fn (s string) split_nth(delim string, nth int) []string {
 			i = 1
 			for ch in s {
 				if nth > 0 && i >= nth {
-					res << s[i..]
+					res << s[i - 1..]
 					break
 				}
 				res << ch.ascii_str()
@@ -938,7 +938,7 @@ pub fn (s string) rsplit_nth(delim string, nth int) []string {
 		0 {
 			for i >= 0 {
 				if nth > 0 && res.len == nth - 1 {
-					res << s[..i]
+					res << s[..i + 1]
 					break
 				}
 				res << s[i].ascii_str()
diff --git a/vlib/builtin/string_test.v b/vlib/builtin/string_test.v
index d17f40fec8..1882166b2c 100644
--- a/vlib/builtin/string_test.v
+++ b/vlib/builtin/string_test.v
@@ -183,6 +183,15 @@ fn test_split_nth() {
 	assert e.split_nth(',,', 3).len == 3
 	assert e.split_nth(',', -1).len == 12
 	assert e.split_nth(',', 3).len == 3
+	f := '1:2:3'
+	assert f.split_nth(':', 2) == ['1', '2:3']
+	assert f.rsplit_nth(':', 2) == ['3', '1:2']
+	g := '123'
+	assert g.split_nth('', 2) == ['1', '23']
+	assert g.rsplit_nth('', 2) == ['3', '12']
+	h := ''
+	assert h.split_nth('', 2) == []
+	assert h.rsplit_nth('', 2) == []
 }
 
 fn test_rsplit_nth() {