fix(ecs-patterns): target group ID changes without setting feature flag (#36199)

### Issue # (if applicable)

Closes #36149

### Reason for this change

The feature flag did not stop the target group ID of the ALB to change if the load balancer was private.

### Description of changes

The target group ID will not change if the feature flag is not set and remain as `ECS`.

### Describe any new or updated permissions being added

No new permissions are added.

### Description of how you validated changes

Unit test added.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: Abogical

packages/@aws-cdk-testing/framework-integ/test/aws-ecs-patterns/test/fargate/integ.alb-fargate-service-public-private-switch.ts

@@ -3,8 +3,13 @@ import * as ecs from 'aws-cdk-lib/aws-ecs';
 import * as cdk from 'aws-cdk-lib';
 import * as integ from '@aws-cdk/integ-tests-alpha';
 import * as ecsPatterns from 'aws-cdk-lib/aws-ecs-patterns';
+import { ECS_PATTERNS_UNIQUE_TARGET_GROUP_ID } from 'aws-cdk-lib/cx-api';
 
-const app = new cdk.App();
+const app = new cdk.App({
+  postCliContext: {
+    [ECS_PATTERNS_UNIQUE_TARGET_GROUP_ID]: true,
+  },
+});
 const stack = new cdk.Stack(app, 'aws-ecs-integ-alb-fargate-public-private-switch');
 
 const vpc = new ec2.Vpc(stack, 'Vpc', { maxAzs: 2, restrictDefaultSecurityGroup: false });

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2-targets/test/integ.alb-target.js.snapshot/TestStack.assets.json

@@ -477,7 +477,7 @@
     "DefaultActions": [
      {
       "TargetGroupArn": {
-       "Ref": "ServiceLBPublicListenerECSPrivateGroup93D5832E"
+       "Ref": "ServiceLBPublicListenerECSGroup0CC8688C"
       },
       "Type": "forward"
      }
@@ -489,7 +489,7 @@
     "Protocol": "HTTP"
    }
   },
-  "ServiceLBPublicListenerECSPrivateGroup93D5832E": {
+  "ServiceLBPublicListenerECSGroup0CC8688C": {
    "Type": "AWS::ElasticLoadBalancingV2::TargetGroup",
    "Properties": {
     "Port": 80,
@@ -524,7 +524,7 @@
       "ContainerName": "nginx",
       "ContainerPort": 80,
       "TargetGroupArn": {
-       "Ref": "ServiceLBPublicListenerECSPrivateGroup93D5832E"
+       "Ref": "ServiceLBPublicListenerECSGroup0CC8688C"
       }
      }
     ],
@@ -554,7 +554,7 @@
     }
    },
    "DependsOn": [
-    "ServiceLBPublicListenerECSPrivateGroup93D5832E",
+    "ServiceLBPublicListenerECSGroup0CC8688C",
     "ServiceLBPublicListener46709EAA",
     "TaskTaskRoleE98524A1"
    ]
@@ -674,7 +674,7 @@
     }
    },
    "DependsOn": [
-    "ServiceLBPublicListenerECSPrivateGroup93D5832E",
+    "ServiceLBPublicListenerECSGroup0CC8688C",
     "ServiceLBPublicListener46709EAA"
    ]
   }

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2-targets/test/integ.alb-target.js.snapshot/TestStack.template.json

@@ -526,8 +526,8 @@ export abstract class ApplicationLoadBalancedServiceBase extends Construct {
       // Include both internetFacing and loadBalancerName in target group ID
       targetGroupId = `ECS${props.loadBalancerName ?? ''}${internetFacing ? '' : 'Private'}`;
     } else {
-      // Legacy behavior: only include internetFacing
-      targetGroupId = internetFacing ? 'ECS' : 'ECSPrivate';
+      // Legacy behavior
+      targetGroupId = 'ECS';
     }
 
     this.targetGroup = this.listener.addTargets(targetGroupId, targetProps);

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2-targets/test/integ.alb-target.js.snapshot/integ.json

@@ -2450,71 +2450,6 @@ describe('NetworkLoadBalancedFargateService', () => {
     });
   });
 
-  test('target group has different logical ID for public vs private load balancer', () => {
-    // GIVEN
-    const stack1 = new cdk.Stack();
-    const stack2 = new cdk.Stack();
-
-    // WHEN - Create public load balancer service
-    new ecsPatterns.ApplicationLoadBalancedFargateService(stack1, 'Service', {
-      taskImageOptions: {
-        image: ecs.ContainerImage.fromRegistry('/aws/aws-example-app'),
-      },
-      publicLoadBalancer: true,
-    });
-
-    // WHEN - Create private load balancer service
-    new ecsPatterns.ApplicationLoadBalancedFargateService(stack2, 'Service', {
-      taskImageOptions: {
-        image: ecs.ContainerImage.fromRegistry('/aws/aws-example-app'),
-      },
-      publicLoadBalancer: false,
-    });
-
-    // THEN - Target groups should have different logical IDs
-    const template1 = Template.fromStack(stack1);
-    const template2 = Template.fromStack(stack2);
-
-    // Public load balancer should create target group with 'ECS' suffix
-    template1.hasResourceProperties('AWS::ElasticLoadBalancingV2::TargetGroup', {
-      Port: 80,
-      Protocol: 'HTTP',
-      TargetType: 'ip',
-    });
-
-    // Private load balancer should create target group with 'ECSPrivate' suffix
-    template2.hasResourceProperties('AWS::ElasticLoadBalancingV2::TargetGroup', {
-      Port: 80,
-      Protocol: 'HTTP',
-      TargetType: 'ip',
-    });
-
-    // Verify the logical IDs are different by checking the generated CloudFormation
-    const resources1 = template1.toJSON().Resources;
-    const resources2 = template2.toJSON().Resources;
-
-    const targetGroup1Keys = Object.keys(resources1).filter(key =>
-      resources1[key].Type === 'AWS::ElasticLoadBalancingV2::TargetGroup',
-    );
-    const targetGroup2Keys = Object.keys(resources2).filter(key =>
-      resources2[key].Type === 'AWS::ElasticLoadBalancingV2::TargetGroup',
-    );
-
-    // Should have exactly one target group each
-    expect(targetGroup1Keys).toHaveLength(1);
-    expect(targetGroup2Keys).toHaveLength(1);
-
-    // The logical IDs should be different
-    expect(targetGroup1Keys[0]).not.toEqual(targetGroup2Keys[0]);
-
-    // Public should contain 'ECS' but not 'ECSPrivate'
-    expect(targetGroup1Keys[0]).toContain('ECS');
-    expect(targetGroup1Keys[0]).not.toContain('ECSPrivate');
-
-    // Private should contain 'ECSPrivate'
-    expect(targetGroup2Keys[0]).toContain('ECSPrivate');
-  });
-
   describe('ECS_PATTERNS_UNIQUE_TARGET_GROUP_ID feature flag', () => {
     test('with feature flag enabled - generates unique target group IDs', () => {
       // GIVEN
@@ -2577,6 +2512,36 @@ describe('NetworkLoadBalancedFargateService', () => {
       // Should use legacy naming (contains 'ECS' but not unique identifier)
       expect(targetGroupKeys).toHaveLength(1);
       expect(targetGroupKeys[0]).toContain('ECS');
+      expect(targetGroupKeys[0]).not.toContain('ECSPrivate');
+    });
+
+    test('with feature flag disabled - uses legacy target group naming for private load balancer', () => {
+      // GIVEN
+      const featureFlag = { [cxapi.ECS_PATTERNS_UNIQUE_TARGET_GROUP_ID]: false };
+      const app = new cdk.App({
+        context: featureFlag,
+      });
+      const stack = new cdk.Stack(app, 'TestStack');
+
+      // WHEN
+      new ecsPatterns.ApplicationLoadBalancedFargateService(stack, 'Service', {
+        taskImageOptions: {
+          image: ecs.ContainerImage.fromRegistry('/aws/aws-example-app'),
+        },
+        publicLoadBalancer: false,
+      });
+
+      // THEN
+      const template = Template.fromStack(stack);
+      const resources = template.toJSON().Resources;
+      const targetGroupKeys = Object.keys(resources).filter(key =>
+        resources[key].Type === 'AWS::ElasticLoadBalancingV2::TargetGroup',
+      );
+
+      // Should use legacy naming (contains 'ECS' but not unique identifier)
+      expect(targetGroupKeys).toHaveLength(1);
+      expect(targetGroupKeys[0]).toContain('ECS');
+      expect(targetGroupKeys[0]).not.toContain('ECSPrivate');
     });
 
     test('without feature flag - uses default behavior', () => {