From e56b6c1cbac3b1f6e5c24d715d1fa5e823dc37f3 Mon Sep 17 00:00:00 2001
From: Hillgrove <github@hillgrove.dk>
Date: Sun, 19 Apr 2026 18:03:22 +0200
Subject: [PATCH] fix(lsp): clamp char index to rope length in char_to_position

Prevents a panic when a diagnostic span's end offset lands past
the end of the rope. Fixes kdl-org/vscode-kdl#29
---
 tools/kdl-lsp/src/main.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/kdl-lsp/src/main.rs b/tools/kdl-lsp/src/main.rs
index f8f003d..8a8fb70 100644
--- a/tools/kdl-lsp/src/main.rs
+++ b/tools/kdl-lsp/src/main.rs
@@ -160,6 +160,7 @@ impl LanguageServer for Backend {
 }
 
 fn char_to_position(char_idx: usize, rope: &Rope) -> Position {
+    let char_idx = char_idx.min(rope.len_chars());
     let line_idx = rope.char_to_line(char_idx);
     let line_char_idx = rope.line_to_char(line_idx);
     let column_idx = char_idx - line_char_idx;