instantiator: when applying DS rules, must also swap anchors

Lib/fontmake/instantiator.py

@@ -582,25 +582,32 @@ def swap_glyph_names(font: ufoLib2.Font, name_old: str, name_new: str):
     glyph_old.drawPoints(p)
     glyph_swap.width = glyph_old.width
 
-    glyph_old.clear()
+    glyph_old.clearContours()
+    glyph_old.clearComponents()
     p = glyph_old.getPointPen()
     glyph_new.drawPoints(p)
     glyph_old.width = glyph_new.width
 
-    glyph_new.clear()
+    glyph_new.clearContours()
+    glyph_new.clearComponents()
     p = glyph_new.getPointPen()
     glyph_swap.drawPoints(p)
     glyph_new.width = glyph_swap.width
 
-    # 2. Remap components.
+    # 2. Swap anchors.
+    glyph_swap.anchors = glyph_old.anchors
+    glyph_old.anchors = glyph_new.anchors
+    glyph_new.anchors = glyph_swap.anchors
+
+    # 3. Remap components.
     for g in font:
         for c in g.components:
             if c.baseGlyph == name_old:
                 c.baseGlyph = name_new
             elif c.baseGlyph == name_new:
                 c.baseGlyph = name_old
 
-    # 3. Swap literal names in kerning.
+    # 4. Swap literal names in kerning.
     kerning_new = {}
     for first, second in font.kerning.keys():
         value = font.kerning[(first, second)]
@@ -615,7 +622,7 @@ def swap_glyph_names(font: ufoLib2.Font, name_old: str, name_new: str):
         kerning_new[(first, second)] = value
     font.kerning = kerning_new
 
-    # 4. Swap names in groups.
+    # 5. Swap names in groups.
     for group_name, group_members in font.groups.items():
         group_members_new = []
         for name in group_members:

tests/data/SwapGlyphNames/A.ufo/glyphs/a.glif

@@ -2,6 +2,8 @@
 <glyph name="a" format="2">
   <advance width="600"/>
   <unicode hex="0061"/>
+  <anchor x="351" y="0" name="bottom"/>
+  <anchor x="351" y="613" name="top"/>
   <outline>
     <contour>
       <point x="113.0" y="500.0" type="line"/>

tests/data/SwapGlyphNames/A.ufo/glyphs/a.swap.glif

@@ -1,6 +1,8 @@
 <?xml version='1.0' encoding='UTF-8'?>
 <glyph name="a.swap" format="2">
   <advance width="666.0"/>
+  <anchor x="153" y="0" name="bottom"/>
+  <anchor x="153" y="316" name="top"/>
   <outline>
     <contour>
       <point x="127" y="500" type="line"/>

tests/test_instantiator.py

@@ -3,6 +3,7 @@
 import fontTools.designspaceLib as designspaceLib
 import pytest
 import ufoLib2
+from ufoLib2.objects.anchor import Anchor
 
 import fontmake.instantiator
 
@@ -140,6 +141,16 @@ def test_swap_glyph_names(data_dir):
     ]
     assert sorted(c.baseGlyph for c in ufo["aaa.swap"].components) == ["a", "a", "y"]
 
+    # Test swapped anchors.
+    assert ufo["a"].anchors == [
+        Anchor(x=153, y=0, name="bottom"),
+        Anchor(x=153, y=316, name="top"),
+    ]
+    assert ufo["a.swap"].anchors == [
+        Anchor(x=351, y=0, name="bottom"),
+        Anchor(x=351, y=613, name="top"),
+    ]
+
     # Test swapped glyph kerning.
     assert ufo.kerning == {
         ("public.kern1.a", "x"): 10,