SNS: allow SetSubscriptionAttributes to unset FilterPolicy (#7251)

moto/sns/models.py

@@ -732,8 +732,17 @@ class SNSBackend(BaseBackend):
             raise SNSNotFoundError(
                 "Subscription does not exist", template="wrapped_single_error"
             )
+        # AWS does not return the FilterPolicy scope if the FilterPolicy is not set
+        # if the FilterPolicy is set and not the FilterPolicyScope, it returns the default value
+        attributes = {**subscription.attributes}
+        if "FilterPolicyScope" in attributes and not attributes.get("FilterPolicy"):
+            attributes.pop("FilterPolicyScope", None)
+            attributes.pop("FilterPolicy", None)
 
-        return subscription.attributes
+        elif "FilterPolicy" in attributes and "FilterPolicyScope" not in attributes:
+            attributes["FilterPolicyScope"] = "MessageAttributes"
+
+        return attributes
 
     def set_subscription_attributes(self, arn: str, name: str, value: Any) -> None:
         if name not in [
@@ -753,6 +762,7 @@ class SNSBackend(BaseBackend):
         subscription = _subscription[0]
 
         if name == "FilterPolicy":
+            if value:
                 filter_policy = json.loads(value)
                 # we validate the filter policy differently depending on the scope
                 # we need to always set the scope first
@@ -762,6 +772,9 @@ class SNSBackend(BaseBackend):
                 subscription._filter_policy_matcher = FilterPolicyMatcher(
                     filter_policy, filter_policy_scope
                 )
+            else:
+                subscription._filter_policy = None
+                subscription._filter_policy_matcher = None
 
         subscription.attributes[name] = value
 

tests/test_sns/test_subscriptions_boto3.py

@@ -393,6 +393,7 @@ def test_set_subscription_attributes():
     assert attrs["Attributes"]["RawMessageDelivery"] == "true"
     assert attrs["Attributes"]["DeliveryPolicy"] == delivery_policy
     assert attrs["Attributes"]["FilterPolicy"] == filter_policy
+    assert attrs["Attributes"]["FilterPolicyScope"] == "MessageAttributes"
 
     filter_policy_scope = "MessageBody"
     conn.set_subscription_attributes(
@@ -405,6 +406,17 @@ def test_set_subscription_attributes():
 
     assert attrs["Attributes"]["FilterPolicyScope"] == filter_policy_scope
 
+    # test unsetting a filter policy
+    conn.set_subscription_attributes(
+        SubscriptionArn=subscription_arn,
+        AttributeName="FilterPolicy",
+        AttributeValue="",
+    )
+
+    attrs = conn.get_subscription_attributes(SubscriptionArn=subscription_arn)
+    assert "FilterPolicy" not in attrs["Attributes"]
+    assert "FilterPolicyScope" not in attrs["Attributes"]
+
     # not existing subscription
     with pytest.raises(ClientError):
         conn.set_subscription_attributes(
@@ -413,7 +425,7 @@ def test_set_subscription_attributes():
             AttributeValue="true",
         )
     with pytest.raises(ClientError):
-        attrs = conn.get_subscription_attributes(SubscriptionArn="invalid")
+        conn.get_subscription_attributes(SubscriptionArn="invalid")
 
     # invalid attr name
     with pytest.raises(ClientError):