topic.subscribeQueue across stacks creates a cyclic dependency

[eladb]

Repro:

import cdk = require('@aws-cdk/cdk');
import sns = require('@aws-cdk/aws-sns');
import sqs = require('@aws-cdk/aws-sqs');

const app = new cdk.App();

const stackWithTopic = new cdk.Stack(app, 'stack-with-topic');
const stackWithQueue = new cdk.Stack(app, 'stack-with-queue');

const queue = new sqs.Queue(stackWithQueue, 'MyQueue');
const topic = new sns.Topic(stackWithTopic, 'MyTopic');

topic.subscribeQueue(queue);

app.run();

Error:

Stack 'stack-with-topic' already depends on stack 'stack-with-queue'. Adding this dependency would create a cyclic reference.

This is because sns.Subscription references the queue and sqs.QueuePolicy references the topic. I wonder if the right solution to this is to create the subscription in the scope of the queue and not in the scope of the topic.

[eladb]

@rix0rrr what do you think?

[rix0rrr]

For this particular case, I think that's a pragmatic solution.

The generically correct way of dealing with these is to put the QueuePolicy into a 3rd stack (automatically), but we don't have support for that yet.