tools/spec: don't use xml nodes in the Command constructor

tools/spec.py

@@ -422,17 +422,12 @@ class Command(Type):
         def is_pointer(self):
             return '*' in self.param
 
-    def __init__(self, node):
-        assert node.tag == "command"
-        proto = node.find('proto')
-        name = proto.find('name').text
+    def __init__(self, name: str, result: str, params: List[Param], depends: List[str] = None):
         super().__init__(name)
 
-        self.result = proto.find('type').text
-        self.params = [self.Param(p) for p in node.findall('./param')]
-        self.depends += [self.result]
-        for p in self.params:
-            self.depends += p.depends
+        self.result = result
+        self.params = params
+        self.depends += depends or []
 
     def declare(self):
         return 'extern "C" %(result)s %(name)s (%(params)s) noexcept;' % {
@@ -687,7 +682,16 @@ def parse_commands(reg: Registry, root):
             reg.types[name] = AliasValue(name, node.attrib['alias'])
             continue
 
-        reg.types[name] = Command(node)
+        proto = node.find('proto')
+        name = proto.find('name').text
+
+        result = proto.find('type').text
+        params = [Command.Param(p) for p in node.findall('./param')]
+        depends = [result]
+        for p in params:
+            depends += p.depends
+
+        reg.types[name] = Command(name, result, params, depends)
 
 
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