Drop disabled prefixes and classes in minimal mode

Partially fixes #761 and
#763.

Lib/glyphsLib/builder/features.py

@@ -100,9 +100,22 @@ def _to_ufo_features(  # noqa: C901
     else:
         expander = TokenExpander(font, master)
 
+    prefixes = []
+    for prefix in font.featurePrefixes:
+        if prefix.disabled and minimal:
+            continue
+        strings = []
+        if prefix.name != ANONYMOUS_FEATURE_PREFIX_NAME:
+            strings.append("# Prefix: %s\n" % prefix.name)
+        strings.append(autostr(prefix.automatic))
+        strings.append(expander.expand(prefix.code))
+        prefixes.append("".join(strings))
+
+    prefix_str = "\n\n".join(prefixes)
+
     class_defs = []
     for class_ in font.classes:
-        if not class_.active:  # TODO: (gs) write them commented out as with the features to be able to round trip
+        if class_.disabled and minimal:
             continue
         prefix = "@" if not class_.name.startswith("@") else ""
         name = prefix + class_.name

tests/builder/features_test.py

@@ -739,6 +739,42 @@ def test_roundtrip_feature_prefix_with_only_a_comment(ufo_module):
     assert prefix_r.code == "#include(../family.fea)"
 
 
+def test_drop_disabled_class(ufo_module):
+    font = to_glyphs([ufo_module.Font()])
+    class_ = classes.GSClass(name="Class1", code="a b")
+    class_.disabled = True
+    font.classes.append(class_)
+
+    class_ = classes.GSClass(name="Class2", code="c d")
+    font.classes.append(class_)
+
+    (ufo,) = to_ufos(font, ufo_module=ufo_module, minimal=True)
+    assert ufo.features.text == dedent(
+        """\
+        @Class2 = [ c d
+        ];
+    """
+    )
+
+
+def test_drop_disabled_prefix(ufo_module):
+    font = to_glyphs([ufo_module.Font()])
+    prefix = classes.GSFeaturePrefix(name="Prefix1", code="# test 1")
+    prefix.disabled = True
+    font.featurePrefixes.append(prefix)
+
+    prefix = classes.GSFeaturePrefix(name="Prefix2", code="# test 2")
+    font.featurePrefixes.append(prefix)
+
+    (ufo,) = to_ufos(font, ufo_module=ufo_module, minimal=True)
+    assert ufo.features.text == dedent(
+        """\
+        # Prefix: Prefix2
+        # test 2
+    """
+    )
+
+
 def test_drop_disabled_feature(ufo_module):
     font = to_glyphs([ufo_module.Font()])
     feature = classes.GSFeature(name="ccmp", code="sub a by a.ccmp1 a.ccmp2;")