Merge pull request #1897 from khaledhosny/issue-1896

[feaLib] Check lookup index in chaining lookups
fonttools · Apr 27, 2020 · 1d2d5b3 · 1d2d5b3
2 parents effb560 + e0c49a1
commit 1d2d5b3
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diff --git a/Lib/fontTools/feaLib/builder.py b/Lib/fontTools/feaLib/builder.py
@@ -1263,6 +1263,10 @@ def build(self):
             st.PosLookupRecord = []
             for sequenceIndex, l in enumerate(lookups):
                 if l is not None:
+                    if l.lookup_index is None:
+                        raise FeatureLibError('Missing index of the specified '
+                            'lookup, might be a substitution lookup',
+                            self.location)
                     rec = otTables.PosLookupRecord()
                     rec.SequenceIndex = sequenceIndex
                     rec.LookupListIndex = l.lookup_index
@@ -1310,6 +1314,10 @@ def build(self):
             st.SubstLookupRecord = []
             for sequenceIndex, l in enumerate(lookups):
                 if l is not None:
+                    if l.lookup_index is None:
+                        raise FeatureLibError('Missing index of the specified '
+                            'lookup, might be a positioning lookup',
+                            self.location)
                     rec = otTables.SubstLookupRecord()
                     rec.SequenceIndex = sequenceIndex
                     rec.LookupListIndex = l.lookup_index

diff --git a/Tests/feaLib/builder_test.py b/Tests/feaLib/builder_test.py
@@ -430,6 +430,28 @@ def test_lookup_inside_feature_aalt(self):
             "Lookup blocks cannot be placed inside 'aalt' features",
             self.build, "feature aalt {lookup L {} L;} aalt;")
 
+    def test_chain_subst_refrences_GPOS_looup(self):
+        self.assertRaisesRegex(
+            FeatureLibError,
+            "Missing index of the specified lookup, might be a positioning lookup",
+            self.build,
+            "lookup dummy { pos a 50; } dummy;"
+            "feature test {"
+            "    sub a' lookup dummy b;"
+            "} test;"
+        )
+
+    def test_chain_pos_refrences_GSUB_looup(self):
+        self.assertRaisesRegex(
+            FeatureLibError,
+            "Missing index of the specified lookup, might be a substitution lookup",
+            self.build,
+            "lookup dummy { sub a by A; } dummy;"
+            "feature test {"
+            "    pos a' lookup dummy b;"
+            "} test;"
+        )
+
     def test_extensions(self):
         class ast_BaseClass(ast.MarkClass):
             def asFea(self, indent=""):