From b20b83a2df0f1bf9026324c57e73f5824bd2516e Mon Sep 17 00:00:00 2001
From: RyogaK <14046676+RyogaK@users.noreply.github.com>
Date: Sat, 4 Apr 2026 02:52:21 +0900
Subject: [PATCH] fix: exclude wide characters that would exceed endColumn

When endColumn falls in the middle of a wide character (CJK or emoji),
the character is now excluded so that the result never exceeds the
requested column range.

Fixes #43
---
 index.js |  5 ++++-
 test.js  | 23 ++++++++++++++++++++---
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/index.js b/index.js
index f031913..e1a2f4f 100755
--- a/index.js
+++ b/index.js
@@ -216,7 +216,10 @@ export default function sliceAnsi(string, start, end) {
 	let include = false;
 
 	for (const [tokenIndex, token] of tokens.entries()) {
-		let isPastEnd = end !== undefined && position >= end;
+		let isPastEnd = end !== undefined && (
+			position >= end
+			|| (token.type === 'character' && !token.isGraphemeContinuation && position + token.visibleWidth > end)
+		);
 		if (
 			isPastEnd
 			&& token.type !== 'character'
diff --git a/test.js b/test.js
index 6c1e315..980a3ac 100755
--- a/test.js
+++ b/test.js
@@ -201,7 +201,8 @@ test('supports fullwidth characters', t => {
 });
 
 test('supports unicode surrogate pairs', t => {
-	t.is(sliceAnsi('a\uD83C\uDE00BC', 0, 2), 'a\uD83C\uDE00');
+	t.is(sliceAnsi('a\uD83C\uDE00BC', 0, 2), 'a');
+	t.is(sliceAnsi('a\uD83C\uDE00BC', 0, 3), 'a\uD83C\uDE00');
 });
 
 test('does not split grapheme clusters with combining marks', t => {
@@ -308,15 +309,31 @@ test('does not lose fullwidth characters', t => {
 	t.is(sliceAnsi('古古test', 0), '古古test');
 });
 
+// See https://github.com/chalk/slice-ansi/issues/43
+test('does not exceed endColumn for wide characters', t => {
+	const input = 'あいう';
+	t.is(sliceAnsi(input, 0, 0), '');
+	t.is(sliceAnsi(input, 0, 1), '');
+	t.is(sliceAnsi(input, 0, 2), 'あ');
+	t.is(sliceAnsi(input, 0, 3), 'あ');
+	t.is(sliceAnsi(input, 0, 4), 'あい');
+	t.is(sliceAnsi(input, 0, 5), 'あい');
+	t.is(sliceAnsi(input, 0, 6), 'あいう');
+});
+
 test('does not split regional-indicator flag graphemes', t => {
 	const input = 'A🇮🇱B';
-	t.is(sliceAnsi(input, 1, 2), '🇮🇱');
+	t.is(sliceAnsi(input, 0, 1), 'A');
+	t.is(sliceAnsi(input, 1, 2), '');
+	t.is(sliceAnsi(input, 1, 3), '🇮🇱');
 	t.is(sliceAnsi(input, 2, 3), '');
+	t.is(sliceAnsi(input, 3, 4), 'B');
 });
 
 test('does not split styled regional-indicator flag graphemes', t => {
 	const input = '\u001B[31m🇮🇱\u001B[39m';
-	t.is(sliceAnsi(input, 0, 1), input);
+	t.is(sliceAnsi(input, 0, 1), '');
+	t.is(sliceAnsi(input, 0, 2), input);
 	t.is(sliceAnsi(input, 1, 2), '');
 });