How to handle input UFO with bad glyph names?

tests/featureWriters/kernFeatureWriter_test.py

@@ -10,6 +10,7 @@
 
 from ufo2ft.featureCompiler import parseLayoutFeatures
 from ufo2ft.featureWriters import KernFeatureWriter, ast
+from ufo2ft.errors import InvalidFontData
 
 import pytest
 from . import FeatureWriterTest
@@ -722,6 +723,15 @@ def test_kern_RTL_and_DFLT_numbers(self, FontClass):
             """
         )
 
+    def test_error_on_bad_glyph_name(self, FontClass):
+        # One glyph has an invalid glyph name (in fea syntax): "V,"
+        glyphs = {"A": ord('A'), "V,": ord("V")}
+        kerning = {("A", "V,"): -40}
+        features = "languagesystem latn dflt;"
+        ufo = makeUFO(FontClass, glyphs, kerning=kerning, features=features)
+        with pytest.raises(InvalidFontData):
+            generated = self.writeFeatures(ufo)
+
 
 if __name__ == "__main__":
     import sys

tests/featureWriters/markFeatureWriter_test.py

@@ -13,6 +13,7 @@
     parseAnchorName,
 )
 from ufo2ft.featureCompiler import parseLayoutFeatures
+from ufo2ft.errors import InvalidFontData
 
 import pytest
 from . import FeatureWriterTest
@@ -579,6 +580,14 @@ def test_all_features(self, testufo):
             """
         )
 
+    def test_error_on_bad_glyph_name(self, testufo):
+        # Add a glyph with an invalid name to the test UFO: "f_i,"
+        testufo.newGlyph("a,").appendAnchor({"name": "top", "x": 100, "y": 200})
+        writer = MarkFeatureWriter()
+        feaFile = ast.FeatureFile()
+        with pytest.raises(InvalidFontData):
+            writer.write(testufo, feaFile)
+
 
 if __name__ == "__main__":
     import sys