[voltLib] Add feature definition

Lib/fontTools/voltLib/ast.py

@@ -32,7 +32,15 @@ class ScriptDefinition(ast.Statement):
         self.langs = langs
 
 class LangSysDefinition(ast.Statement):
-    def __init__(self, location, name, tag):
+    def __init__(self, location, name, tag, features):
         ast.Statement.__init__(self,location)
         self.name = name
         self.tag = tag
+        self.features = features
+
+class FeatureDefinition(ast.Statement):
+    def __init__(self, location, name, tag, lookups):
+        ast.Statement.__init__(self,location)
+        self.name = name
+        self.tag = tag
+        self.lookups = lookups

Lib/fontTools/voltLib/parser.py

@@ -111,9 +111,31 @@ class Parser(object):
         name = self.expect_string_()
         self.expect_keyword_("TAG")
         tag = self.expect_string_()
-        def_langsys = ast.LangSysDefinition(location, name, tag)
+        features = []
+        while self.next_token_ != "END_LANGSYS":
+            self.advance_lexer_()
+            feature = self.parse_feature_()
+            self.expect_keyword_("END_FEATURE")
+            features.append(feature)
+        def_langsys = ast.LangSysDefinition(location, name, tag, features)
         return def_langsys
 
+    def parse_feature_(self):
+        assert self.is_cur_keyword_("DEF_FEATURE")
+        location = self.cur_token_location_
+        self.expect_keyword_("NAME")
+        name = self.expect_string_()
+        self.expect_keyword_("TAG")
+        tag = self.expect_string_()
+        lookups = []
+        while self.next_token_ != "END_FEATURE":
+            # self.advance_lexer_()
+            self.expect_keyword_("LOOKUP")
+            lookup = self.expect_string_()
+            lookups.append(lookup)
+        feature = ast.FeatureDefinition(location, name, tag, lookups)
+        return feature
+
     def parse_unicode_values_(self):
         location = self.cur_token_location_
         unicode_values = self.expect_string_().split(',')

Lib/fontTools/voltLib/parser_test.py

@@ -114,6 +114,38 @@ class ParserTest(unittest.TestCase):
                          ("Romanian",
                           "ROM "))
 
+    def test_feature(self):
+        [def_script] = self.parse(
+            'DEF_SCRIPT NAME "Latin" TAG "latn"\n'
+            'DEF_LANGSYS NAME "Romanian" TAG "ROM "\n'
+            'DEF_FEATURE NAME "Fractions" TAG "frac"\n'
+            'LOOKUP "fraclookup"\n'
+            'END_FEATURE\n'
+            'END_LANGSYS\n'
+            'END_SCRIPT'
+        ).statements
+        def_feature = def_script.langs[0].features[0]
+        self.assertEqual((def_feature.name, def_feature.tag,
+                          def_feature.lookups),
+                         ("Fractions",
+                          "frac",
+                          ["fraclookup"]))
+        [def_script] = self.parse(
+            'DEF_SCRIPT NAME "Latin" TAG "latn"\n'
+            'DEF_LANGSYS NAME "Romanian" TAG "ROM "\n'
+            'DEF_FEATURE NAME "Kerning" TAG "kern"\n'
+            'LOOKUP "kern1" LOOKUP "kern2"\n'
+            'END_FEATURE\n'
+            'END_LANGSYS\n'
+            'END_SCRIPT'
+        ).statements
+        def_feature = def_script.langs[0].features[0]
+        self.assertEqual((def_feature.name, def_feature.tag,
+                          def_feature.lookups),
+                         ("Kerning",
+                          "kern",
+                          ["kern1", "kern2"]))
+
     def setUp(self):
         self.tempdir = None
         self.num_tempfiles = 0