From 1ad74d1ddffa0aafae21b794acabee0fda634897 Mon Sep 17 00:00:00 2001
From: dotCooCoo <RobertLeeLW@gmail.com>
Date: Tue, 3 Nov 2026 16:52:40 -0800
Subject: [PATCH] Type: reject doubly signed OpenType feature tags

---
 crates/engine/src/cmd/textstyles/tests.rs | 15 +++++++++++++++
 crates/text/src/features.rs               |  5 ++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/crates/engine/src/cmd/textstyles/tests.rs b/crates/engine/src/cmd/textstyles/tests.rs
index 90bb32bbb..19da4c8ab 100644
--- a/crates/engine/src/cmd/textstyles/tests.rs
+++ b/crates/engine/src/cmd/textstyles/tests.rs
@@ -335,6 +335,21 @@ fn character_style_color_and_features_are_checked() {
     assert_eq!(s.doc().unwrap().history.undo.len(), undo);
 }
 
+#[test]
+fn text_style_rejects_doubly_signed_feature_tags() {
+    let (mut s, id) = session_with_text("Text");
+    let before = runs(&s, id);
+    let undo = s.doc().unwrap().history.undo.len();
+    for cmd in ["text.setStyle", "text.setRangeStyle"] {
+        for tag in ["--liga", "+-dnom", "-+ss01", "++liga"] {
+            let error = s.execute(cmd, &json!({"id": id, "start": 0, "end": 4, "features": [tag]})).unwrap_err().to_string();
+            assert!(error.contains(&format!("`{tag}`")), "{cmd}: {error}");
+        }
+    }
+    assert_eq!(runs(&s, id), before);
+    assert_eq!(s.doc().unwrap().history.undo.len(), undo);
+}
+
 #[test]
 fn style_paints_count_as_swatch_uses_and_gradient_stops_are_checked() {
     let (mut s, _) = session_with_text("Text");
diff --git a/crates/text/src/features.rs b/crates/text/src/features.rs
index 3a75f2579..eac3b3c3f 100644
--- a/crates/text/src/features.rs
+++ b/crates/text/src/features.rs
@@ -146,7 +146,7 @@ impl OtFeatures {
 
     /// Is `tag` (optionally prefixed with `-` or `+`) one this set understands?
     pub fn known_tag(tag: &str) -> bool {
-        let t = tag.trim_start_matches(['-', '+']);
+        let t = tag.strip_prefix(['-', '+']).unwrap_or(tag);
         matches!(t, "liga" | "calt" | "dlig" | "smcp" | "frac" | "onum" | "tnum" | "ordn" | "swsh") || EXTRA_FEATURES.contains(&t)
     }
 
@@ -306,6 +306,9 @@ mod tests {
             assert!(OtFeatures::known_tag(t), "{t}");
         }
         assert!(!OtFeatures::known_tag("ss21"));
+        for tag in ["--liga", "+-dnom", "-+ss01", "++liga"] {
+            assert!(!OtFeatures::known_tag(tag), "{tag}");
+        }
         let o = OtFeatures::from_tags(["ss03", "pnum", "sups", "-liga"]);
         assert_eq!(o.to_tags(), vec!["-liga", "ss03", "pnum", "sups"]);
         assert_eq!(OtFeatures::from_tags(["ss03", "-ss03"]).to_tags(), Vec::<String>::new(), "turned off again");