(custom-resources): broken usage of list tokens in parameters

[MrArnoldPalmer]

Referencing a token that is a list of strings within a custom resource parameters object results in a reference to an undefined parameter.

Reproduction Steps

Reproduction App

import * as cdk from '@aws-cdk/core';
import * as ec2 from '@aws-cdk/aws-ec2';
import * as cr from '@aws-cdk/custom-resources';

export class BadrefStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    const vpc = new ec2.Vpc(this, 'MyVpc');

    const vpce = new ec2.InterfaceVpcEndpoint(this, 'MyVpcEndpoint', {
      vpc,
      service: {
        name: 'com.amazonaws.us-east-1.execute-api',
        port: 443
      }
    });

    const policy = cr.AwsCustomResourcePolicy.fromSdkCalls({
      resources: cr.AwsCustomResourcePolicy.ANY_RESOURCE,
    });

    new cr.AwsCustomResource(this, 'GetEdnpointIp', {
      policy,
      onUpdate: {
        service: 'EC2',
        action: 'DescribeNetworkInterfaces',
        outputPath: 'NetworkInterfaces.${index}.PrivateIpAddress',
        parameters: {
          // NetworkInterfaceIds: vpce.vpcEndpointNetworkInterfaceIds,
          NetworkInterfaceIds: [cdk.Token.asList(cdk.Stack.of(this).toJsonString(cdk.Fn.join('","', vpce.vpcEndpointNetworkInterfaceIds)))]
        },
        physicalResourceId: cr.PhysicalResourceId.of('resourceid'),
      }
    });
  }
}

What did you expect to happen?

Deploys the app to cloudformation with the CR having access to the vpce network interface IDs as json.

What actually happened?

cdk deploy results in

Template error: instance of Fn::GetAtt references undefined resource CdkJsonStringify3

Environment

• CDK CLI Version : 1.97.0
• Framework Version: 1.97.0
• Node.js Version: 14.15.4
• OS : MacOS
• Language (Version): all

Other

Related to some recent changes:
#13465
#13544

---

This is 🐛 Bug Report

[rix0rrr]

Not sure what to make of the following:

          // NetworkInterfaceIds: vpce.vpcEndpointNetworkInterfaceIds,
          NetworkInterfaceIds: [cdk.Token.asList(cdk.Stack.of(this).toJsonString(cdk.Fn.join('","', vpce.vpcEndpointNetworkInterfaceIds)))]

Is the first one broken, the 2nd one a workaround?

[Token.asList(...)]

Is confusing me a little because it would end up as [[ x, y, z]] which seems not intended. At the same time, that shouldn't cause the error you're seeing.

[rix0rrr]

❤️ on the repro though. Feature haz test but I can confirm this example fails. Hey-ho, a-digging we will go

[rix0rrr]

  CdkJsonStringify1:
    Type: Custom::AWSCDKCfnJsonStringify
    Properties:

            - Fn::GetAtt:
                - CdkJsonStringify3
                - Value

😳

Must be because of separate prepare/synth cycles.

🤬

[MrArnoldPalmer]

Oooh sorry, yeah the second one was an attempt at a workaround but both failed.

[github-actions]

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