fix(elbv2): fix disabling proxy protocol v2 attribute for NetworkTarg…

…etGroup (#4596)

fixes #4574

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

@@ -54,8 +54,8 @@ export class NetworkTargetGroup extends TargetGroupBase implements INetworkTarge
 
     this.listeners = [];
 
-    if (props.proxyProtocolV2) {
-      this.setAttribute('proxy_protocol_v2.enabled', 'true');
+    if (props.proxyProtocolV2 != null) {
+      this.setAttribute('proxy_protocol_v2.enabled', props.proxyProtocolV2 ? 'true' : 'false');
     }
 
     this.addTarget(...(props.targets || []));

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

@@ -0,0 +1,52 @@
+import { expect, haveResource } from '@aws-cdk/assert';
+import cdk = require('@aws-cdk/core');
+import { Test } from 'nodeunit';
+import elbv2 = require('../../lib');
+
+export = {
+  'Enable proxy protocol v2 attribute for target group'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+
+    // WHEN
+    new elbv2.NetworkTargetGroup(stack, 'Group', {
+        port: 80,
+        proxyProtocolV2: true
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::ElasticLoadBalancingV2::TargetGroup', {
+      TargetGroupAttributes: [
+        {
+          Key: 'proxy_protocol_v2.enabled',
+          Value: 'true'
+        }
+      ]
+    }));
+
+    test.done();
+  },
+
+  'Disable proxy protocol v2 for attribute target group'(test: Test) {
+    // GIVEN
+    const stack = new cdk.Stack();
+
+    // WHEN
+    new elbv2.NetworkTargetGroup(stack, 'Group', {
+        port: 80,
+        proxyProtocolV2: false
+    });
+
+    // THEN
+    expect(stack).to(haveResource('AWS::ElasticLoadBalancingV2::TargetGroup', {
+      TargetGroupAttributes: [
+        {
+          Key: 'proxy_protocol_v2.enabled',
+          Value: 'false'
+        }
+      ]
+    }));
+
+    test.done();
+  },
+};