Drop non-plist glyph libs instead of failing

These exist in a number of old real-world UFO files, and it doesn't seem
particularly useful to just fail to read those files at all.

This also brings in the log crate, for logging these dropped errors.

Author: cmyr

Cargo.toml

@@ -41,6 +41,7 @@ thiserror = "2.0"
 indexmap = { version = "2.0.0", features = ["serde"] }
 base64 = "0.22"
 close_already = "0.3"
+log = "0.4"
 
 [dev-dependencies]
 failure = "0.1.6"

src/glyph/parse.rs

@@ -308,12 +308,20 @@ impl<'names> GlifParser<'names> {
         }
 
         let plist_slice = &raw_xml[start..end];
-        let dict = plist::Value::from_reader_xml(plist_slice)
-            .map_err(|_| GlifLoadError::Parse(ErrorKind::BadLib))?
-            .into_dictionary()
-            .ok_or(GlifLoadError::Parse(ErrorKind::LibMustBeDictionary))?;
+        match plist::Value::from_reader_xml(plist_slice)
+            .map_err(|_| GlifLoadError::Parse(ErrorKind::BadLib))
+            .and_then(|x| {
+                x.into_dictionary().ok_or(GlifLoadError::Parse(ErrorKind::LibMustBeDictionary))
+            }) {
+            Ok(dict) => {
+                // we used to error if this was malformed but there are a number of early UFO files
+                // in the wild that store arbitrary xml in the lib, which doesn't parse as a plist.
+                // Instead of failing to parse these files, we prefer to just skip the dicts.
+                self.glyph.lib = dict;
+            }
+            Err(e) => log::info!("glyph {} contains invalid lib: '{e}'", self.glyph.name),
+        }
 
-        self.glyph.lib = dict;
         Ok(())
     }
 

src/glyph/tests.rs

@@ -318,8 +318,9 @@ fn bad_angle() {
 }
 
 #[test]
-#[should_panic(expected = "LibMustBeDictionary")]
-fn lib_must_be_dict() {
+// in a number of older UFO files in the wild glyphs can contain dictionaries
+// with arbitrary non-plsit XML:
+fn skip_non_lib_dictionary() {
     let data = r#"
 <?xml version="1.0" encoding="UTF-8"?>
 <glyph name="period" format="2">
@@ -328,7 +329,8 @@ fn lib_must_be_dict() {
     </lib>
 </glyph>
 "#;
-    let _ = parse_glyph(data.as_bytes()).unwrap();
+    let glyph = parse_glyph(data.as_bytes()).unwrap();
+    assert!(glyph.lib.is_empty());
 }
 
 #[test]