Cross stack vpc causes unresolved resource dependencies error

Hi, creating a vpc in a child stack (not nested), and creating some resources, that depend on the vpc, in another child stack will result in a ValidationError. I was able to reproduce this with application loadbalancers (only internet facing) aswell as an aurora cluster (public and private).

Reproduction Steps

import cdk = require('@aws-cdk/core');
import { NetworkStack } from './Network-stack';
import { InstancesStack } from './Instances-stack';

export class TestStack extends cdk.Stack {
    constructor(scope: cdk.App, id: string, props: cdk.StackProps) {
        super(scope, id, props);
        const network = new NetworkStack(this, "NetworkStack", props);

        new InstancesStack(this, "Instances", {
            env: props.env,
            network: network
        });
    }
}

import cdk = require('@aws-cdk/core');
import ec2 = require('@aws-cdk/aws-ec2');

export class NetworkStack extends cdk.Stack {
    public readonly vpc: ec2.Vpc;

    constructor(scope: cdk.Stack, id: string, props: cdk.StackProps) {
        super(scope, id, props);

        this.vpc = new ec2.Vpc(this, "vpc", {
            cidr: "10.0.0.0/16",
            maxAzs: 3,
            subnetConfiguration: [
                {
                    cidrMask: 20,
                    subnetType: ec2.SubnetType.PRIVATE,
                    name: "subnet-private"
                },
                {
                    cidrMask: 20,
                    subnetType: ec2.SubnetType.PUBLIC,
                    name: "subnet-public"
                }
            ],
            natGateways: 2
        });
    }
}

import cdk = require('@aws-cdk/core'); 
import loadbalancer = require('@aws-cdk/aws-elasticloadbalancingv2');
import { NetworkStack } from './Network-stack';
 
export interface theseProps extends cdk.StackProps { 
    network: NetworkStack
} 
 
export class InstancesStack extends cdk.Stack {
 
    constructor(scope: cdk.Stack, id: string, props: theseProps) { 
        super(scope, id, props);
        
        new loadbalancer.ApplicationLoadBalancer(this, "testLB", {
            vpc: props.network.vpc,
            internetFacing: true
        });
    } 
}

Error Log

cdk deploy *
TestStack
TestStack: deploying...
TestStack: creating CloudFormation changeset...

 ✅  TestStack (no changes)

Stack ARN:
arn:aws:cloudformation:eu-west-1:123456789:stack/TestStack/f7358b50-ec24-11e9-8e0e-02c03455965c
TestStackNetworkStackE68E9FD0
TestStackNetworkStackE68E9FD0: deploying...
TestStackNetworkStackE68E9FD0: creating CloudFormation changeset...
...

 ✅  TestStackNetworkStackE68E9FD0

Outputs:
TestStackNetworkStackE68E9FD0.ExportsOutputRefvpcsubnetpublicSubnet1SubnetF125D982384FC8F2 = subnet-05bb64c9b53308b7c
TestStackNetworkStackE68E9FD0.ExportsOutputRefvpcA2121C384D1B3CDE = vpc-02997d94566f805bf
TestStackNetworkStackE68E9FD0.ExportsOutputRefvpcsubnetpublicSubnet2Subnet2731CC5E2E3D2FF3 = subnet-0b862d79b52959ec6
TestStackNetworkStackE68E9FD0.ExportsOutputRefvpcsubnetpublicSubnet3Subnet7494E9BC8FCFC236 = subnet-03944fc3ed16a79b4

Stack ARN:
arn:aws:cloudformation:eu-west-1:123456789:stack/TestStackNetworkStackE68E9FD0/2d351770-ec25-11e9-9415-06982f8c16e4
TestStackInstancesF0B37D31
TestStackInstancesF0B37D31: deploying...
TestStackInstancesF0B37D31: creating CloudFormation changeset...

 ❌  TestStackInstancesF0B37D31 failed: ValidationError: Template format error: Unresolved resource dependencies [vpcsubnetpublicSubnet3DefaultRoute3905C18B, vpcsubnetpublicSubnet2DefaultRoute7436D83A, vpcsubnetpublicSubnet1Defau
ltRouteA1448C8B] in the Resources block of the template
Template format error: Unresolved resource dependencies [vpcsubnetpublicSubnet3DefaultRoute3905C18B, vpcsubnetpublicSubnet2DefaultRoute7436D83A, vpcsubnetpublicSubnet1DefaultRouteA1448C8B] in the Resources block of the template  

Environment

• CLI Version : 1.16.232
• Framework Version: 1.12.0
• OS : Windows 10
• Language : TypeScript

---

This is 🐛 Bug Report

[eladb]

Apologies for the confusion, managed to reproduce this in 1.18.0:

import { Stack, App } from '@aws-cdk/core';
import ec2 = require('@aws-cdk/aws-ec2');
import elb = require('@aws-cdk/aws-elasticloadbalancingv2');

const app = new App();

const root = new Stack(app, 'Root');

const stack1 = new Stack(root, 'Network');
const vpc = new ec2.Vpc(stack1, 'Vpc');

const stack2 = new Stack(root, 'Instances');
new elb.ApplicationLoadBalancer(stack2, 'LoadBalancer', { 
  vpc, 
  internetFacing: true 
});

app.synth();

Validated that this is going to be resolved by #5211

[cmckni3]

I can confirm this is fixed in master. I did a full build and linked dependencies into a project last night.

cdk deploy worked perfectly with cross stack VPCs. No more template reference error could not reference MyAppVPCRoute. 👍