bool(glyph) is False for empty glyphs.. fix logic for notdefGlyph

we should check 'if notdefGlyph is not None', otherwise 'if notdefGlyph' returns False for empty glyphs and we hit the else branch, leading to incompatible glyphs whose variations get ignored by varLib...

Lib/ufo2ft/outlineCompiler.py

@@ -262,7 +262,7 @@ def makeMissingRequiredGlyphs(font, glyphSet, sfntVersion, notdefGlyph=None):
             return
 
         reverseContour = sfntVersion == "\000\001\000\000"
-        if notdefGlyph:
+        if notdefGlyph is not None:
             notdefGlyph = _copyGlyph(notdefGlyph, reverseContour=reverseContour)
         else:
             unitsPerEm = otRound(getAttrWithFallback(font.info, "unitsPerEm"))

tests/integration_test.py

@@ -7,6 +7,7 @@
 
 import pytest
 from fontTools.pens.boundsPen import BoundsPen
+from fontTools.pens.transformPen import TransformPen
 from fontTools.ttLib.tables._g_l_y_f import (
     OVERLAP_COMPOUND,
     flagCubic,
@@ -455,8 +456,10 @@ def test_compileTTF_glyf1_not_allQuadratic(self, testufo):
         assert ttf["head"].glyphDataFormat == 1
 
     @staticmethod
-    def drawCurvedContour(glyph):
+    def drawCurvedContour(glyph, transform=None):
         pen = glyph.getPen()
+        if transform is not None:
+            pen = TransformPen(pen, transform)
         pen.moveTo((500, 0))
         pen.curveTo((500, 277.614), (388.072, 500), (250, 500))
         pen.curveTo((111.928, 500), (0, 277.614), (0, 0))
@@ -497,9 +500,9 @@ def test_compileVariableTTF_notdefGlyph_with_curves(self, designspace):
 
         # First we draw an additional contour containing cubic curves in the Regular
         # and Bold's .notdef glyphs
-        for src_idx in (0, 2):
+        for src_idx, transform in ((0, (1, 0, 0, 1, 0, 0)), (2, (2, 0, 0, 2, 0, 0))):
             notdef = designspace.sources[src_idx].font[".notdef"]
-            self.drawCurvedContour(notdef)
+            self.drawCurvedContour(notdef, transform)
         assert ".notdef" not in designspace.sources[1].font.layers["Medium"]
 
         # this must NOT fail!
@@ -508,6 +511,10 @@ def test_compileVariableTTF_notdefGlyph_with_curves(self, designspace):
         # and because allQuadratic=True, we expect .notdef contains no cubic curves
         assert not any(f & flagCubic for f in vf["glyf"][".notdef"].flags)
 
+        # ensure .notdef has variations and was NOT dropped as incompatible,
+        # varLib only warns: https://github.com/fonttools/fonttools/issues/2572
+        assert ".notdef" in vf["gvar"].variations
+
 
 if __name__ == "__main__":
     sys.exit(pytest.main(sys.argv))