fonttools · khaledhosny · Apr 23, 2025 · Apr 17, 2025 · Apr 17, 2025
diff --git a/Lib/fontTools/feaLib/ast.py b/Lib/fontTools/feaLib/ast.py
@@ -1583,15 +1583,20 @@ def asFea(self, indent=""):
                 res += " ".join(map(asFea, self.prefix)) + " "
             res += " ".join(
                 [
-                    asFea(x[0]) + "'" + ((" " + x[1].asFea()) if x[1] else "")
+                    asFea(x[0])
+                    + "'"
+                    + ((" " + x[1].asFea()) if x[1] is not None else "")
                     for x in self.pos
                 ]
             )
             if len(self.suffix):
                 res += " " + " ".join(map(asFea, self.suffix))
         else:
             res += " ".join(
-                [asFea(x[0]) + " " + (x[1].asFea() if x[1] else "") for x in self.pos]
+                [
+                    asFea(x[0]) + " " + (x[1].asFea() if x[1] is not None else "")
+                    for x in self.pos
+                ]
             )
         res += ";"
         return res

diff --git a/Lib/fontTools/otlLib/builder.py b/Lib/fontTools/otlLib/builder.py
@@ -1545,6 +1545,8 @@ def add_pos(self, location, glyph, otValueRecord):
             otValueRection: A ``otTables.ValueRecord`` used to position the
                 glyph.
         """
+        if otValueRecord is None:
+            otValueRecord = ValueRecord()
         if not self.can_add(glyph, otValueRecord):
             otherLoc = self.locations[glyph]
             raise OpenTypeLibError(

diff --git a/Tests/feaLib/ast_test.py b/Tests/feaLib/ast_test.py
@@ -13,12 +13,34 @@ def test_valuerecord_none(self):
         statement = ast.ValueRecord(xPlacement=10, xAdvance=20)
         self.assertEqual(statement.asFea(), "<10 0 20 0>")
 
+    def test_valuerecord_empty(self):
+        statement = ast.ValueRecord()
+        self.assertEqual(statement.asFea(), "<NULL>")
+
     def test_non_object_location(self):
         el = ast.Element(location=("file.fea", 1, 2))
         self.assertEqual(el.location.file, "file.fea")
         self.assertEqual(el.location.line, 1)
         self.assertEqual(el.location.column, 2)
 
+    def test_single_pos_statement_empty_valuerecord(self):
+        statement = ast.SinglePosStatement(
+            pos=[(ast.GlyphName("a"), ast.ValueRecord())],
+            prefix=[],
+            suffix=[],
+            forceChain=False,
+        )
+        self.assertEqual(statement.asFea(), "pos a <NULL>;")
+
+    def test_single_pos_statement_empty_valuerecord_chain(self):
+        statement = ast.SinglePosStatement(
+            pos=[(ast.GlyphName("a"), ast.ValueRecord())],
+            prefix=[],
+            suffix=[],
+            forceChain=True,
+        )
+        self.assertEqual(statement.asFea(), "pos a' <NULL>;")
+
 
 if __name__ == "__main__":
     import sys

diff --git a/Tests/feaLib/builder_test.py b/Tests/feaLib/builder_test.py
@@ -91,6 +91,7 @@ class BuilderTest(unittest.TestCase):
         MarkBasePosSubtable
         MarkLigPosSubtable
         MarkMarkPosSubtable
+        single_pos_NULL
     """.split()
 
     VARFONT_AXES = [

diff --git a/Tests/feaLib/data/single_pos_NULL.fea b/Tests/feaLib/data/single_pos_NULL.fea
@@ -0,0 +1,8 @@
+# Both lookups should result in SinglePos lookup with a ValueFormat 0
+lookup test1 {
+    pos A <NULL>;
+} test1;
+
+lookup test2 {
+    pos B' <NULL>;
+} test2;
diff --git a/Tests/feaLib/data/single_pos_NULL.ttx b/Tests/feaLib/data/single_pos_NULL.ttx
@@ -0,0 +1,57 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ttFont>
+
+  <GPOS>
+    <Version value="0x00010000"/>
+    <ScriptList>
+      <!-- ScriptCount=0 -->
+    </ScriptList>
+    <FeatureList>
+      <!-- FeatureCount=0 -->
+    </FeatureList>
+    <LookupList>
+      <!-- LookupCount=3 -->
+      <Lookup index="0">
+        <LookupType value="1"/>
+        <LookupFlag value="0"/>
+        <!-- SubTableCount=1 -->
+        <SinglePos index="0" Format="1">
+          <Coverage>
+            <Glyph value="A"/>
+          </Coverage>
+          <ValueFormat value="0"/>
+        </SinglePos>
+      </Lookup>
+      <Lookup index="1">
+        <LookupType value="8"/>
+        <LookupFlag value="0"/>
+        <!-- SubTableCount=1 -->
+        <ChainContextPos index="0" Format="3">
+          <!-- BacktrackGlyphCount=0 -->
+          <!-- InputGlyphCount=1 -->
+          <InputCoverage index="0">
+            <Glyph value="B"/>
+          </InputCoverage>
+          <!-- LookAheadGlyphCount=0 -->
+          <!-- PosCount=1 -->
+          <PosLookupRecord index="0">
+            <SequenceIndex value="0"/>
+            <LookupListIndex value="2"/>
+          </PosLookupRecord>
+        </ChainContextPos>
+      </Lookup>
+      <Lookup index="2">
+        <LookupType value="1"/>
+        <LookupFlag value="0"/>
+        <!-- SubTableCount=1 -->
+        <SinglePos index="0" Format="1">
+          <Coverage>
+            <Glyph value="B"/>
+          </Coverage>
+          <ValueFormat value="0"/>
+        </SinglePos>
+      </Lookup>
+    </LookupList>
+  </GPOS>
+
+</ttFont>
diff --git a/Tests/feaLib/parser_test.py b/Tests/feaLib/parser_test.py
@@ -1021,6 +1021,16 @@ def test_gpos_type_1_chained_exception4(self):
         with self.assertRaisesRegex(FeatureLibError, "Positioning values are allowed"):
             doc = self.parse("feature kern {" "    pos a' b c 123 d;" "} kern;")
 
+    def test_gpos_type_1_null(self):
+        doc = self.parse("feature test {pos a <NULL>;} test;")
+        pos = doc.statements[0].statements[0]
+        self.assertEqual(pos.asFea(), "pos a <NULL>;")
+
+    def test_gpos_type_1_null_chained(self):
+        doc = self.parse("feature test {pos a' <NULL>;} test;")
+        pos = doc.statements[0].statements[0]
+        self.assertEqual(pos.asFea(), "pos a' <NULL>;")
+
     def test_gpos_type_2_format_a(self):
         doc = self.parse(
             "feature kern {" "    pos [T V] -60 [a b c] <1 2 3 4>;" "} kern;"