Add a method to freeze a ResourceDefinition

Change-Id: Idcbdd0efbc9c3b38c39b8ac1e64e9057fad15899

heat/engine/rsrc_defn.py

@@ -92,6 +92,33 @@ class ResourceDefinitionCore(object):
                                               function.Function))
             self._hash ^= _hash_data(update_policy)
 
+    def freeze(self, **overrides):
+        """
+        Return a frozen resource definition, with all functions resolved.
+
+        This return a new resource definition with fixed data (containing no
+        intrinsic functions). Named arguments passed to this method override
+        the values passed as arguments to the constructor.
+        """
+        def arg_item(attr_name):
+            name = attr_name.lstrip('_')
+            if name in overrides:
+                value = overrides[name]
+                if not value and getattr(self, attr_name) is None:
+                    value = None
+            else:
+                value = function.resolve(getattr(self, attr_name))
+
+            return name, value
+
+        args = ('name', 'resource_type', '_properties', '_metadata',
+                '_depends', '_deletion_policy', '_update_policy',
+                'description')
+
+        defn = type(self)(**dict(arg_item(a) for a in args))
+        defn._frozen = True
+        return defn
+
     def reparse(self, stack, template):
         """
         Reinterpret the resource definition in the context of a new stack.
@@ -99,6 +126,9 @@ class ResourceDefinitionCore(object):
         This returns a new resource definition, with all of the functions
         parsed in the context of the specified stack and template.
         """
+        assert not getattr(self, '_frozen', False), \
+            "Cannot re-parse a frozen definition"
+
         def reparse_snippet(snippet):
             return template.parse(stack, copy.deepcopy(snippet))
 

heat/tests/test_rsrc_defn.py

@@ -112,6 +112,20 @@ class ResourceDefinitionTest(HeatTestCase):
         up = rd.update_policy(schema)
         self.assertEqual('bar', up['SomePolicy']['Foo'])
 
+    def test_freeze(self):
+        rd = self.make_me_one_with_everything()
+
+        frozen = rd.freeze()
+        self.assertEqual('bar', frozen._properties['Foo'])
+        self.assertEqual('quux', frozen._metadata['Baz'])
+
+    def test_freeze_override(self):
+        rd = self.make_me_one_with_everything()
+
+        frozen = rd.freeze(metadata={'Baz': 'wibble'})
+        self.assertEqual('bar', frozen._properties['Foo'])
+        self.assertEqual('wibble', frozen._metadata['Baz'])
+
     def test_render_hot(self):
         rd = self.make_me_one_with_everything()