SecurityGroup connections between stacks lead to cyclic references

I’ve notice two cases where I can get a cyclic reference exception when referencing one stack twice within another:

1. In the example below the props.databaseCluster is coming from a data stack - and I can use either reference on the first or last line to it, but not both.

    // app stack
    const DATABASE_URL = `postgresql://${props.databaseCluster.clusterEndpoint.hostname}`

    const container = taskDefinition.addContainer('app', {
      image: ecs.ContainerImage.fromEcrRepository(props.ecr, props.branch),
      environment: { DATABASE_URL }
    })

    // create a SG for Fargate service
    const secGroup = new ec2.SecurityGroup(this, 'DataAccessSecGrp', {
      vpc: props.vpc,
      allowAllOutbound: true
    })

    // let ECS see RDS
    props.databaseCluster.connections.allowDefaultPortFrom(secGroup, 'allow PG')

1. I’ve also noticed that I get the same exception if I export two different things from the data stack and try to reference them in the app stack - for example I defined the security group in the data stack and export and try to use it in app stack (along with the databaseCluster export).

The error is something like:

Error: Stack ‘data’ already depends on stack ‘app’. Adding this dependency would create a cyclic reference.

[Plasma]

I’m a bit stumped too, for example, defining an Rds instance in one stack, then dependent stacks wanting to attach SG rules seems to easily raise this error.

[sgronblo]

Is this supposed to work this way already? I tried creating a BastionLinuxHost in my FoundationStack. Then I create a DB instance in DBStack. Now an attempt to allow SG access from bastion to db using: this.db.connections.allowDefaultPortFrom(props.bastionHost, 'Allow DB access from bastion') seems to result in a cyclic dependency?