java (dotnet?) regression: unable to use structs with escape hatches

[eladb]

When passing in jsii generated structs to APIs that accept Object, the "$jsii.struct marker is retained. This means that users are not able to use jsii structs, for example, in property overrides, which is a regression from a previous version.

Reproduction Steps

Topic topic = Topic.Builder.create(this, "MyTopic").build();
CfnTopic cfnTopic = (CfnTopic) topic.getNode().getDefaultChild();
cfnTopic.addPropertyOverride("Subscriptions", Collections.singletonList(CfnTopic.SubscriptionProperty.builder()
        .endpoint("endpoint")
        .protocol("Foo")
        .build()));

Result is:

{
  "Type" : "AWS::SNS::Topic",
  "Properties" : {
    "Subscriptions" : [ {
      "$jsii.struct" : {
        "fqn" : "@aws-cdk/aws-sns.CfnTopic.SubscriptionProperty",
        "data" : {
          "endpoint" : "endpoint",
          "protocol" : "Foo"
        }
      }
    } ]
}

Expected:

{
  "Type" : "AWS::SNS::Topic",
  "Properties" : {
    "Subscriptions" : [ {
        "fqn" : "@aws-cdk/aws-sns.CfnTopic.SubscriptionProperty",
        "data" : {
          "endpoint" : "endpoint",
          "protocol" : "Foo"
        }
     }
   ]
}

Error Log

Environment

• Framework Version: 1.16.3.DEVPREVIEW (jsii 0.20.6)
• OS :
• Language : Java (probably .NET as well)

Other

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This is 🐛 Bug Report

[eladb]

@RomainMuller why do we need to even tag structs? Isn't the whole point for them to be passed as simple values? There shouldn't be a difference between a struct and a JSON object sent over the wire.

[RomainMuller]

The issue was when deserializing unions, a type hint was necessary in order to safely operate. There was a p0 bug that made SAM impossible to use without that. See aws/jsii#822 (which is what this behavior was introduced to fix)