Handle MATH input more carefully

Lib/ufo2ft/outlineCompiler.py

@@ -1186,24 +1186,20 @@ def setupTable_MATH(self):
         for name, glyph in self.allGlyphs.items():
             if GLYPHS_MATH_VARIANTS_KEY in glyph.lib:
                 variants = glyph.lib[GLYPHS_MATH_VARIANTS_KEY]
-                if "hVariants" in variants:
-                    h_variants[name] = [
-                        (n, self._bboxWidth(n)) for n in variants["hVariants"]
-                    ]
-                if "vVariants" in variants:
-                    v_variants[name] = [
-                        (n, self._bboxHeight(n)) for n in variants["vVariants"]
-                    ]
-                if "hAssembly" in variants:
-                    parts = variants["hAssembly"]
+                if names := variants.get("hVariants"):
+                    h_variants[name] = [(n, self._bboxWidth(n)) for n in names]
+                if names := variants.get("vVariants"):
+                    v_variants[name] = [(n, self._bboxHeight(n)) for n in names]
+                if parts := variants.get("hAssembly"):
+                    assert all(len(part) == 4 for part in parts), "Invalid assembly"
                     h_assemblies[name] = (
                         [(*part, self._bboxWidth(part[0])) for part in parts],
                         # If the last part has italic correction, we use it as
                         # the assembly's.
                         italics_correction.pop(parts[-1][0], 0),
                     )
-                if "vAssembly" in variants:
-                    parts = variants["vAssembly"]
+                if parts := variants.get("vAssembly"):
+                    assert all(len(part) == 4 for part in parts), "Invalid assembly"
                     v_assemblies[name] = (
                         [(*part, self._bboxHeight(part[0])) for part in parts],
                         # If the last part has italic correction, we use it as

tests/outlineCompiler_test.py

@@ -1406,9 +1406,10 @@ def test_achVendId_space_padded_if_less_than_4_chars(
     assert font["OS/2"].achVendID == expected
 
 
-def test_MATH_table(FontClass):
+@pytest.mark.parametrize("compile", [compileTTF, compileOTF])
+def test_MATH_table(FontClass, compile):
     ufo = FontClass(getpath("TestMathFont-Regular.ufo"))
-    result = compileTTF(ufo)
+    result = compile(ufo)
     assert "MATH" in result
 
     math = result["MATH"].table
@@ -1427,6 +1428,53 @@ def test_MATH_table(FontClass):
 
     assert set(math.MathGlyphInfo.ExtendedShapeCoverage.glyphs) == extendedShapes
 
+    assert set(math.MathVariants.VertGlyphCoverage.glyphs) == {
+        "parenright",
+        "parenleft",
+    }
+    assert math.MathVariants.VertGlyphConstruction
+    assert len(math.MathVariants.VertGlyphConstruction) == 2
+    assert (
+        math.MathVariants.VertGlyphConstruction[0].GlyphAssembly.ItalicsCorrection.Value
+        == 0
+    )
+    assert (
+        len(math.MathVariants.VertGlyphConstruction[0].GlyphAssembly.PartRecords) == 3
+    )
+
+    assert not math.MathVariants.HorizGlyphCoverage
+    assert not math.MathVariants.HorizGlyphConstruction
+
+
+@pytest.mark.parametrize("compile", [compileTTF, compileOTF])
+@pytest.mark.parametrize(
+    "attribute",
+    [
+        "vAssembly",
+        "hAssembly",
+        "vVariants",
+        "hVariants",
+    ],
+)
+def test_MATH_table_ignore_empty(FontClass, compile, attribute):
+    # Should not raise becaise of empty assembly/variants
+    ufo = FontClass(getpath("TestMathFont-Regular.ufo"))
+    ufo["parenright"].lib[GLYPHS_MATH_VARIANTS_KEY][attribute] = []
+    compile(ufo)
+
+
+@pytest.mark.parametrize("compile", [compileTTF, compileOTF])
+@pytest.mark.parametrize("attribute", ["vAssembly", "hAssembly"])
+def test_MATH_table_invalid(FontClass, compile, attribute):
+    ufo = FontClass(getpath("TestMathFont-Regular.ufo"))
+    ufo["parenright"].lib[GLYPHS_MATH_VARIANTS_KEY][attribute] = [
+        ["parenright.top", 0, 0],
+        ["parenright.ext", 1, 100, 100],
+        ["parenright.bot", 0, 100, 0],
+    ]
+    with pytest.raises(AssertionError, match="Invalid assembly"):
+        compile(ufo)
+
 
 if __name__ == "__main__":
     import sys