feat: allow classes that inherit Resource to disable __setattr__ validation (#3047)

Author: pradrx

samtranslator/model/__init__.py

@@ -105,7 +105,7 @@ class Resource(ABC):
     # TODO: Make `Resource` an abstract class and not giving `resource_type`/`property_types` initial value.
     resource_type: str = None  # type: ignore
     property_types: Dict[str, PropertyType] = None  # type: ignore
-    _keywords = ["logical_id", "relative_id", "depends_on", "resource_attributes"]
+    _keywords = {"logical_id", "relative_id", "depends_on", "resource_attributes"}
 
     # For attributes in this list, they will be passed into the translated template for the same resource itself.
     _supported_resource_attributes = ["DeletionPolicy", "UpdatePolicy", "Condition", "UpdateReplacePolicy", "Metadata"]
@@ -122,6 +122,11 @@ class Resource(ABC):
     # }
     runtime_attrs: Dict[str, Callable[["Resource"], Any]] = {}  # TODO: replace Any with something more explicit
 
+    # When "validate_setattr" is True, we cannot change the value of any class variables after instantiation unless they
+    # are in "property_types" or "_keywords". We can set this to False in the inheriting class definition so we can
+    # update other class variables as well after instantiation.
+    validate_setattr: bool = True
+
     def __init__(
         self,
         logical_id: Optional[Any],
@@ -313,7 +318,7 @@ def __setattr__(self, name, value):  # type: ignore[no-untyped-def]
         :param value: the value of the attribute to be set
         :raises InvalidResourceException: if an invalid property is provided
         """
-        if name in self._keywords or name in self.property_types:
+        if (name in self._keywords or name in self.property_types) or not self.validate_setattr:
             return super().__setattr__(name, value)
 
         raise InvalidResourceException(

tests/model/test_resource.py

@@ -0,0 +1,38 @@
+from unittest import TestCase
+
+from samtranslator.model import Property, SamResourceMacro
+from samtranslator.model.exceptions import InvalidResourceException
+from samtranslator.model.types import IS_STR
+
+
+class DummyResourceWithValidation(SamResourceMacro):
+    # validate_setattr is set to True in Resource class by default
+    resource_type = "AWS::Serverless:DummyResource"
+    property_types = {"SomeProperty": Property(False, IS_STR), "AnotherProperty": Property(False, IS_STR)}
+
+    def to_cloudformation(self, **kwargs):
+        return []
+
+
+class DummyResourceNoValidation(SamResourceMacro):
+    resource_type = "AWS::Serverless:DummyResource"
+    property_types = {"SomeProperty": Property(False, IS_STR), "AnotherProperty": Property(False, IS_STR)}
+
+    validate_setattr = False
+
+    def to_cloudformation(self, **kwargs):
+        return []
+
+
+class TestResource(TestCase):
+    def test_create_instance_variable_when_validate_setattr_is_true(self):
+        resource = DummyResourceWithValidation("foo")
+        with self.assertRaises(InvalidResourceException):
+            resource.SomeExtraValue = "foo"
+
+    def test_create_instance_variable_when_validate_setattr_is_false(self):
+        resource = DummyResourceNoValidation("foo")
+
+        resource.SomeExtraValue = "foo"
+        resource.AnotherValue = "bar"
+        resource.RandomValue = "baz"