Treat empty guideline names as no name

The UFO spec marks a guideline's name as optional, and some real-world
fonts write it as an explicit empty string (e.g. five UFOs in Google's
Roboto Serif sources). Name validation rejected these, failing the
whole fontinfo.plist (or .glif) load. Treat an empty name as an absent
one when reading, matching fontTools; writing is unchanged and cannot
produce an empty name.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: 2 people

src/fontinfo.rs

@@ -1724,6 +1724,16 @@ mod tests {
         assert_eq!(font_info.open_type_os2_vendor_id, Some("LTTR".into()));
     }
 
+    #[test]
+    fn fontinfo_empty_guideline_name() {
+        let path = "testdata/fontinfo_empty_guideline_name.plist";
+        let font_info: FontInfo = plist::from_file(path).expect("failed to load fontinfo");
+        let guidelines = font_info.guidelines.expect("guidelines should be present");
+        assert_eq!(guidelines.len(), 2);
+        assert_eq!(guidelines[0].name, None);
+        assert_eq!(guidelines[1].name, Some(Name::new_raw("ascender")));
+    }
+
     #[test]
     fn fontinfo2() {
         let path = "testdata/fontinfotest.ufo/fontinfo.plist";

src/glyph/parse.rs

@@ -504,6 +504,9 @@ impl GlifParser {
                     }
                     angle = Some(angle_value);
                 }
+                // The name is optional, and some real-world fonts write it as
+                // an explicit empty string; treat that as no name.
+                b"name" if value.is_empty() => (),
                 b"name" => name = Some(Name::new(&value).map_err(|_| ErrorKind::InvalidName)?),
                 b"color" => color = Some(value.parse().map_err(|_| ErrorKind::BadColor)?),
                 b"identifier" => {

src/glyph/tests.rs

@@ -253,6 +253,19 @@ fn guidelines() {
     assert_eq!(glyph.width, 364.);
 }
 
+#[test]
+fn empty_guideline_name() {
+    let data = r#"
+<?xml version="1.0" encoding="UTF-8"?>
+<glyph name="period" format="2">
+  <guideline y="495" name=""/>
+</glyph>
+"#;
+    let glyph = parse_glyph(data.as_bytes()).unwrap();
+    assert_eq!(glyph.guidelines.len(), 1);
+    assert_eq!(glyph.guidelines[0].name, None);
+}
+
 #[test]
 #[should_panic(expected = "MissingClose")]
 fn missing_close() {

src/guideline.rs

@@ -94,11 +94,24 @@ struct RawGuideline {
     x: Option<f64>,
     y: Option<f64>,
     angle: Option<f64>,
+    #[serde(default, deserialize_with = "deserialize_optional_name")]
     name: Option<Name>,
     color: Option<Color>,
     identifier: Option<Identifier>,
 }
 
+// The name is optional, and some real-world fonts write it as an explicit
+// empty string; treat that as no name instead of failing the load.
+fn deserialize_optional_name<'de, D>(deserializer: D) -> Result<Option<Name>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    match Option::<String>::deserialize(deserializer)? {
+        Some(name) if !name.is_empty() => name.parse::<Name>().map(Some).map_err(de::Error::custom),
+        _ => Ok(None),
+    }
+}
+
 impl Serialize for Guideline {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -171,7 +184,7 @@ impl<'de> Deserialize<'de> for Guideline {
 mod tests {
     use super::*;
 
-    use serde_test::{assert_tokens, Token};
+    use serde_test::{assert_de_tokens, assert_tokens, Token};
 
     #[test]
     fn guideline_parsing() {
@@ -207,4 +220,22 @@ mod tests {
             ],
         );
     }
+
+    #[test]
+    fn empty_guideline_name_is_no_name() {
+        let expected = Guideline::new(Line::Vertical(495.0), None, None, None);
+        assert_de_tokens(
+            &expected,
+            &[
+                Token::Struct { name: "RawGuideline", len: 2 },
+                Token::Str("x"),
+                Token::Some,
+                Token::F64(495.0),
+                Token::Str("name"),
+                Token::Some,
+                Token::Str(""),
+                Token::StructEnd,
+            ],
+        );
+    }
 }

testdata/fontinfo_empty_guideline_name.plist

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>familyName</key>
+	<string>Test</string>
+	<key>guidelines</key>
+	<array>
+		<dict>
+			<key>name</key>
+			<string></string>
+			<key>y</key>
+			<integer>495</integer>
+		</dict>
+		<dict>
+			<key>name</key>
+			<string>ascender</string>
+			<key>y</key>
+			<integer>750</integer>
+		</dict>
+	</array>
+</dict>
+</plist>