@aws-cdk/aws-ec2.InterfaceVpcEndpoint Fails Test

Reproduction Steps

Run the jest test below:

import { InterfaceVpcEndpoint, InterfaceVpcEndpointAwsService, Vpc }
  from "@aws-cdk/aws-ec2";
import { Stack } from "@aws-cdk/core";

test("InterfaceVpcEndpoint", () => {
  // given
  const stack = new Stack();
  const vpc = new Vpc(stack, "TestVpc");
  // when
  new InterfaceVpcEndpoint(stack, "TestEndpoint", {
    lookupSupportedAzs: true,
    service: InterfaceVpcEndpointAwsService.SECRETS_MANAGER,
    vpc: vpc,
  });
});

What did you expect to happen?

The test to succeed.

What actually happened?

The test failed with the error Cannot look up VPC endpoint availability zones if account/region are not specified and stack trace:

at InterfaceVpcEndpoint.validateCanLookupSupportedAzs (node_modules/@aws-cdk/aws-ec2/lib/vpc-endpoint.ts:556:13)
      at InterfaceVpcEndpoint.endpointSubnets (node_modules/@aws-cdk/aws-ec2/lib/vpc-endpoint.ts:526:10)
      at new InterfaceVpcEndpoint (node_modules/@aws-cdk/aws-ec2/lib/vpc-endpoint.ts:480:28)
      at Object.<anonymous> (test/cdk-constructs/interface-vpc-endpoint.test.ts:10:3)

Environment

• CDK CLI Version : 1.103.0 (build bc13a66)
• Framework Version: 1.103.0
• Node.js Version: v14.15.1
• OS : Ubuntu 20.04.2 LTS
• Language (Version): TypeScript 4.2.4
• Jest (Version) : 26.6.3
• ts-jest (version): 26.5.6

Other

I understand this can work without the lookupSupportedAzs: true, param property, but my default profile is configured. I’m unable to determine why this is failing.

---

This is 🐛 Bug Report

[peterwoodworth]

This test will work, even with the dummy account number

it("Should have InterfaceVpcEndpoint", () => {
  // given
  const app = new App();
  const env = { account: '123456789012', region: 'us-west-2' };
  const stack = new Vpctest.VpctestStack(app, "TestStack", {env: env});

  expectCDK(stack).to(haveResourceLike("AWS::EC2::VPCEndpoint"))
});

The code will throw the error you received on creating an InterfaceVpcEndpoint only if both account and region of the stack are undefined and lookupSupportedAzs is true. So it doesn’t actually matter what the values are for this test to pass https://github.com/aws/aws-cdk/blob/7966f8d48c4bff26beb22856d289f9d0c7e7081d/packages/%40aws-cdk/aws-ec2/lib/vpc-endpoint.ts#L546-L557

[fractionalJoe]

Thanks @peterwoodworth, that solved my issue. Is this quirk of CDK_DEFAULT_ACCOUNT (and I’m assuming CDK_DEFAULT_REGION) returning undefined documented anywhere for future reference? I’m aware now but others may have similar questions.