fix(aws-elasticloadbalancingv2): listener dependency (#1146)

Fix taking a listener dependency for Network Load Balancers.

Fixes #1139.

Author: rix0rrr

packages/@aws-cdk/aws-elasticloadbalancingv2/lib/nlb/network-listener.ts

@@ -67,6 +67,7 @@ export class NetworkListener extends BaseListener implements INetworkListener {
     // New default target(s)
     for (const targetGroup of targetGroups) {
       this._addDefaultTargetGroup(targetGroup);
+      targetGroup.registerListener(this);
     }
   }
 

packages/@aws-cdk/aws-elasticloadbalancingv2/lib/nlb/network-target-group.ts

@@ -80,12 +80,22 @@ export class NetworkTargetGroup extends BaseTargetGroup {
  */
 // tslint:disable-next-line:no-empty-interface
 export interface INetworkTargetGroup extends ITargetGroup {
+  /**
+   * Register a listener that is load balancing to this target group.
+   *
+   * Don't call this directly. It will be called by listeners.
+   */
+  registerListener(listener: INetworkListener): void;
 }
 
 /**
  * An imported network target group
  */
 class ImportedNetworkTargetGroup extends BaseImportedTargetGroup implements INetworkTargetGroup {
+  public registerListener(_listener: INetworkListener) {
+    // Nothing to do, we know nothing of our members
+  }
+
   public listenerDependency(): cdk.IDependable {
     return new LazyDependable([]);
   }

packages/@aws-cdk/aws-elasticloadbalancingv2/test/nlb/test.listener.ts

@@ -1,4 +1,4 @@
-import { expect, haveResource } from '@aws-cdk/assert';
+import { expect, haveResource, MatchStyle } from '@aws-cdk/assert';
 import ec2 = require('@aws-cdk/aws-ec2');
 import cdk = require('@aws-cdk/cdk');
 import { Test } from 'nodeunit';
@@ -112,4 +112,34 @@ export = {
 
     test.done();
   },
+
+  'Enable taking a dependency on an NLB target group\'s load balancer'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+    const vpc = new ec2.VpcNetwork(stack, 'Stack');
+    const lb = new elbv2.NetworkLoadBalancer(stack, 'LB', { vpc });
+    const listener = lb.addListener('Listener', { port: 443 });
+    const group = listener.addTargets('Group', {
+      port: 80,
+      targets: [new FakeSelfRegisteringTarget(stack, 'Target', vpc)]
+    });
+
+    // WHEN
+    const resource = new cdk.Resource(stack, 'MyResource', {
+      type: 'SomeResource',
+    });
+    resource.addDependency(group.listenerDependency());
+
+    // THEN
+    expect(stack).toMatch({
+      Resources: {
+        MyResource: {
+          Type: "SomeResource",
+          DependsOn: [ "LBListener49E825B4" ]
+        }
+      }
+    }, MatchStyle.SUPERSET);
+
+    test.done();
+  },
 };