From 1754161dea7853977905d8dec81d48cf97fdda6f Mon Sep 17 00:00:00 2001
From: Ed Page <eopage@gmail.com>
Date: Thu, 1 Aug 2024 13:43:01 -0500
Subject: [PATCH] fix(parser): Correctly bind 'char' boundaries

Fixes #553
---
 crates/core/src/parser/parser.rs |  5 ++++-
 tests/errors.rs                  | 20 +++++++++++++++++---
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/crates/core/src/parser/parser.rs b/crates/core/src/parser/parser.rs
index 92f7ddbcf..a1dbed61e 100644
--- a/crates/core/src/parser/parser.rs
+++ b/crates/core/src/parser/parser.rs
@@ -649,7 +649,10 @@ impl<'a> InvalidLiquidToken<'a> {
         let invalid_token_position = invalid_token_span.start_pos();
         let (offset_l, offset_c) = invalid_token_position.line_col();
         let offset_l = offset_l - 1;
-        let offset_c = offset_c - 1;
+        let offset_c = (0..offset_c)
+            .rev()
+            .find(|i| invalid_token_position.line_of().is_char_boundary(*i))
+            .unwrap_or(0);
 
         let end_position = match next_elements.last() {
             Some(element) => element.as_span().end_pos(),
diff --git a/tests/errors.rs b/tests/errors.rs
index 6879152f1..98edc88a0 100644
--- a/tests/errors.rs
+++ b/tests/errors.rs
@@ -1,8 +1,22 @@
+use snapbox::assert_data_eq;
+use snapbox::str;
+
 #[test]
-#[should_panic]
 fn test_fuzz() {
-    let _ = liquid::ParserBuilder::with_stdlib()
+    match liquid::ParserBuilder::with_stdlib()
         .build()
         .unwrap()
-        .parse("˄{%");
+        .parse("˄{%")
+    {
+        Ok(_) => panic!("should fail"),
+        Err(err) => assert_data_eq!(err.to_string(), str![[r#"
+liquid:  --> 1:3
+  |
+1 | {%
+  |   ^---
+  |
+  = expected Identifier
+
+"#]]),
+    }
 }