eliminate panic on len not lie on boundary

check boundary, add truncate len per 1 as needed till checking pass

1 files changed, 5 insertions, 1 deletions

diff --git a/askama_shared/src/filters/mod.rs b/askama_shared/src/filters/mod.rs
index f5d2720..11216a5 100644
--- a/askama_shared/src/filters/mod.rs
+++ b/askama_shared/src/filters/mod.rs
@@ -161,7 +161,11 @@ pub fn truncate(s: &dyn fmt::Display, len: &usize) -> Result<String> {
     if s.len() < *len {
         Ok(s)
     } else {
-        s.truncate(*len);
+        let mut real_len = *len;
+        while !s.is_char_boundary(real_len) {
+            real_len += 1;
+        }
+        s.truncate(real_len);
         s.push_str("...");
         Ok(s)
     }