ELBv2 - Store default action when modifying listener (#4589)

moto/elbv2/models.py

@@ -1423,6 +1423,7 @@ Member must satisfy regular expression pattern: {}".format(
         if default_actions is not None and default_actions != []:
             # Is currently not validated
             listener.default_actions = default_actions
+            listener._default_rule[0].actions = default_actions
 
         return listener
 

moto/elbv2/responses.py

@@ -607,7 +607,7 @@ class ELBV2Response(BaseResponse):
         protocol = self._get_param("Protocol")
         ssl_policy = self._get_param("SslPolicy")
         certificates = self._get_list_prefix("Certificates.member")
-        default_actions = self._get_list_prefix("DefaultActions.member")
+        default_actions = self._get_params().get("DefaultActions", [])
 
         # Should really move SSL Policies to models
         if ssl_policy is not None and ssl_policy not in [

tests/test_elbv2/test_elbv2_target_groups.py

@@ -521,3 +521,52 @@ def test_create_target_group_with_target_type(target_type):
     group.should.have.key("TargetType").equal(target_type)
     group.shouldnt.have.key("Protocol")
     group.shouldnt.have.key("VpcId")
+
+
+@mock_elbv2
+@mock_ec2
+def test_delete_target_group_after_modifying_listener():
+    client = boto3.client("elbv2", region_name="us-east-1")
+
+    response, vpc, _, _, _, conn = create_load_balancer()
+
+    load_balancer_arn = response.get("LoadBalancers")[0].get("LoadBalancerArn")
+
+    response = client.create_target_group(
+        Name="a-target", Protocol="HTTP", Port=8080, VpcId=vpc.id,
+    )
+    target_group_arn1 = response.get("TargetGroups")[0]["TargetGroupArn"]
+
+    response = client.create_target_group(
+        Name="a-target-2", Protocol="HTTPS", Port=8081, VpcId=vpc.id,
+    )
+    target_group_arn2 = response.get("TargetGroups")[0]["TargetGroupArn"]
+
+    response = conn.create_listener(
+        LoadBalancerArn=load_balancer_arn,
+        Protocol="HTTP",
+        Port=80,
+        DefaultActions=[{"Type": "forward", "TargetGroupArn": target_group_arn1}],
+    )
+    listener_arn = response["Listeners"][0].get("ListenerArn")
+
+    client.modify_listener(
+        ListenerArn=listener_arn,
+        DefaultActions=[{"Type": "forward", "TargetGroupArn": target_group_arn2,}],
+    )
+
+    response = conn.describe_listeners(LoadBalancerArn=load_balancer_arn)
+    default_actions = response["Listeners"][0]["DefaultActions"]
+    default_actions.should.equal(
+        [{"Type": "forward", "TargetGroupArn": target_group_arn2}]
+    )
+
+    # Target Group 1 can now be deleted, as the LB points to group 2
+    client.delete_target_group(TargetGroupArn=target_group_arn1)
+
+    # Sanity check - we're still pointing to group 2
+    response = conn.describe_listeners(LoadBalancerArn=load_balancer_arn)
+    default_actions = response["Listeners"][0]["DefaultActions"]
+    default_actions.should.equal(
+        [{"Type": "forward", "TargetGroupArn": target_group_arn2}]
+    )