(customresources): AwsCustomResource upgrade to v3 breaks reading returned properties

[peterwoodworth]

Describe the bug

In the v3 SDK, lambda response payloads are now encoded as a uint8array -- which can break some implementations e.g. using AwsCustomResource to invoke a lambda function and then attempting to read the payload

Having a stack like this worked on versions before AwsCustomResource updated to SDK v3, like 2.75.0:

    const fn = new lambda.Function(this, "Function", {
      code: lambda.Code.fromInline("exports.handler = async () => { return { statusCode: 200, body: 'Hello World' }; };"),
      handler: "index.handler",
      runtime: lambda.Runtime.NODEJS_16_X,
    });

    const listLambdaFunctionsResource = new cr.AwsCustomResource(this, 'ListLambdaFunctions', {
      installLatestAwsSdk: true,
      onUpdate: {
        service: 'Lambda',
        action: 'invoke',
        parameters: {
          FunctionName: fn.functionName,
        },
        physicalResourceId: cr.PhysicalResourceId.of(Date.now().toString()),
      },
      policy: cr.AwsCustomResourcePolicy.fromStatements([
        new iam.PolicyStatement({
          actions: ['*'],
          resources: ['*'],
          effect: iam.Effect.ALLOW,
        })
      ]),
    });

    const lambdafunctions = listLambdaFunctionsResource.getResponseField('Payload').toString();

    new cdk.CfnOutput(this, 'LambdaFunctions', {
      value: lambdafunctions
    })

However, it will end up failing on a newer version where the AwsCustomResource is updated to SDK v3 like 2.90.0. Checking the CloudTrail logs, you can see that the payload returned looks like this instead of what you would normally expect:

    "Data": {
        "region": "us-east-1",
        "$metadata.httpStatusCode": 200,
        "$metadata.requestId": "f8d6dc59-7cfc-4be7-bf21-7753b3c17636",
        "$metadata.attempts": 1,
        "$metadata.totalRetryDelay": 0,
        "ExecutedVersion": "$LATEST",
        "Payload.0": 123,
        "Payload.1": 34,
        "Payload.2": 115,
        "Payload.3": 116,
        "Payload.4": 97,
        "Payload.5": 116,
        "Payload.6": 117,
        "Payload.7": 115,
        "Payload.8": 67,
        "Payload.9": 111,
        "Payload.10": 100,
        "Payload.11": 101,
        "Payload.12": 34,
        "Payload.13": 58,
        "Payload.14": 50,
        "Payload.15": 48,
        "Payload.16": 48,
        "Payload.17": 44,
        "Payload.18": 34,
        "Payload.19": 98,
        "Payload.20": 111,
        "Payload.21": 100,
        "Payload.22": 121,
        "Payload.23": 34,
        "Payload.24": 58,
        "Payload.25": 34,
        "Payload.26": 72,
        "Payload.27": 101,
        "Payload.28": 108,
        "Payload.29": 108,
        "Payload.30": 111,
        "Payload.31": 32,
        "Payload.32": 87,
        "Payload.33": 111,
        "Payload.34": 114,
        "Payload.35": 108,
        "Payload.36": 100,
        "Payload.37": 34,
        "Payload.38": 125,
        "StatusCode": 200
    }

Expected Behavior

I expected the resource to have readable properties like this being returned from the custom resource as it did prior to the update:

    "Data": {
        "apiVersion": null,
        "region": "us-east-1",
        "StatusCode": 200,
        "ExecutedVersion": "$LATEST",
        "Payload": "{\"statusCode\":200,\"body\":\"Hello World\"}"
    }

Current Behavior

The resource's returned properties aren't parseable

Reproduction Steps

See description

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.90.0

Framework Version

No response

Node.js Version

16

OS

Mac

Language

Typescript

Language Version

No response

Other information

No response

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