Acessing the 'DistributionConfig' of the 'CfnDistribution_' throws an error

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• What is the current behavior? If the current behavior is a 🪲bug🪲: Please provide the steps to reproduce

Create a new CloudFrontWebDistribution, var cf = new CloudFrontWebDistribution Access the underlying CfnDistribution_ with var cfd = cf.Node.FindChild("CFDistribution") as CfnDistribution_; Acessing the DistributionConfig of the CfnDistribution_ throws an error:

Got 'undefined' for non-optional instance of {"abstract":true,"docs":{"remarks":"If this returns an empty array the stack will not be attached.","stability":"stable","summary":"The creation stack of this resolvable which will be appended to errors thrown during resolution."},"immutable":true,"locationInModule":{"filename":"lib/resolvable.ts","line":38},"name":"creationStack","type":{"collection":{"elementtype":{"primitive":"string"},"kind":"array"}}}

• What is the expected behavior (or behavior of feature suggested)?

To be able to see the DistributionConfig of the CfnDistribution_

• What is the motivation / use case for changing the behavior or adding this feature?

I was trying to work around other bugs in the CloudFrontWebDistribution by accessing the DistributionConfig to modify and add it back as overrides

• Please tell us about your environment:

  • CDK CLI Version: 0.39
  • Module Version: 0.39
  • OS: [Windows 10]
  • Language: [C#]

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. associated pull-request, stackoverflow, gitter, etc) Stacktrace:

Got 'undefined' for non-optional instance of {"abstract":true,"docs":{"remarks":"If this returns an empty array the stack will not be attached.","stability":"stable","summary":"The creation stack of this resolvable which will be appended to errors thrown during resolution."},"immutable":true,"locationInModule":{"filename":"lib/resolvable.ts","line":38},"name":"creationStack","type":{"collection":{"elementtype":{"primitive":"string"},"kind":"array"}}}

   at Amazon.JSII.Runtime.Services.Client.TryDeserialize[TResponse](String responseJson)
   at Amazon.JSII.Runtime.Services.Client.ReceiveResponse[TResponse]()
   at Amazon.JSII.Runtime.Deputy.DeputyBase.GetPropertyCore[T](JsiiPropertyAttribute propertyAttribute, Func`2 getFunc)

[McDoit]

I’ve created aws/jsii#2192 to introduce an UnsafeCast<T>() method on DeputyBase (the parent class of AnonymousObject) to allow casting to an arbitrary interface type.

This would allow you to write something along the lines of:

var dcp = (cfd.DistributionConfig as DeputyBase).UnsafeCast<CfnDistribution.DistributionConfigProperty>();

Effectively un-blocking your use-case (and other use-cases that involve property overrides with complex/composite properties).

This might become more elegant in the future, as type unions are supported better (more info at aws/aws-cdk-rfcs#193).

I tried it with CDK 1.70 and JSII 1.14, but I got the following error running the repro stack above: System.InvalidCastException: 'Unable to cast Amazon.JSII.Runtime.Deputy.AnonymousObject into Amazon.CDK.AWS.CloudFront.CfnDistribution+DistributionConfigProperty'

[njlynch]

I verified; just reproduced the above errors (Amazon.JSII.Runtime.Deputy.AnonymousObject/NPE) on CDK 1.68.0.