tools/spec: Don't construct Feature directly from XML

tools/spec.py

@@ -524,18 +524,9 @@ class Require(object):
 
 # -----------------------------------------------------------------------------
 class Feature(Type):
-    def __init__(self, root):
-        assert root.tag == 'feature'
-
-        name = root.attrib['name']
+    def __init__(self, name: str, requires: List[Require] = []):
         super().__init__(name)
-
-        self.requires = []
-        for node in root:
-            if 'require' == node.tag:
-                self.requires.append(Require(node))
-            else:
-                raise RuntimeError("Unhandled feature node")
+        self.requires = requires
 
     def define(self, reg: Registry):
         return "#define %s" % self.name
@@ -701,7 +692,14 @@ def parse_feature(reg: Registry, root):
     name = root.attrib['name']
     assert name not in reg.features
 
-    reg.features[name] = Feature(root)
+    requires = []
+    for node in root:
+        if 'require' == node.tag:
+            requires.append(Require(node))
+        else:
+            raise RuntimeError("Unhandled feature node")
+
+    reg.features[name] = Feature(name, requires)
     reg.types[name] = reg.features[name]
 
 
@@ -915,8 +913,8 @@ def main():
     reg.types['VK_NULL_HANDLE'] = AliasValue("VK_NULL_HANDLE", "nullptr")
 
     # Request serialisation of all features
-    features = [Feature(n) for n in root.findall('./feature')]
-    features = dict((f.name,f) for f in features)
+    #features = [Feature(n) for n in root.findall('./feature')]
+    #features = dict((f.name,f) for f in features)
 
     #reg.extensions['VK_KHR_surface'].apply(reg, platform='xcb')