Java/DotNet: abstract members are not marked as such on their .NET and Java representations.

[rix0rrr]

🐛 Bug Report

In this code:

https://github.com/rix0rrr/jsii-test-drive/blob/master/java/extends-abstract-class/src/main/java/com/myorg/MyCode.java

The subclass of Code is not complete. It is missing an implementation of public abstract readonly isInline: boolean.

This class should have been needed to be marked abstract, but it it isn't.

Impact to CDK

• Abstract members have an implementation in the generated .NET and Java code, allowing classes extending those to omit implementation of some (or all) of the abstract members. While the resulting code compiles, it may fail at run-time due to the missing implementations.
• Workaround: when extending abstract classes, consult the TypeScript API reference to identify all abstract members of the extended type, and make sure to implement all of those. The members will be made abstract in a subsequent release of the CDK for Java and .NET, which will break invalid implementations.

[rix0rrr]

This feels wrong-- the abstract-ness of a member should be mirrored into the JSII bindings.

[nija-at]

Same problem affecting c# - https://github.com/rix0rrr/jsii-test-drive/blob/master/dotnet/serverless/src/Serverless/Program.cs

[rix0rrr]

Accessing the "abstract" member results in a predictable JSII exception:

Unhandled exception. Amazon.JSII.Runtime.JsiiException: Got 'undefined' for non-optional instance of {"abstract":true,"docs":{"stability":"stable","summary":"The name of the function."},"immutable":true,"locationInModule":{"filename":"lib/function-base.ts","line":148},"name":"functionName","overrides":"@aws-cdk/aws-lambda.IFunction","type":{"primitive":"string"}}
   at Amazon.JSII.Runtime.Services.Client.TryDeserialize[TResponse](String responseJson)
   at Amazon.JSII.Runtime.Services.Client.ReceiveResponse[TResponse]()
   at Amazon.JSII.Runtime.Services.Client.Send[TRequest,TResponse](TRequest requestObject)
   at Amazon.JSII.Runtime.Services.Client.Get(GetRequest request)
   at Amazon.JSII.Runtime.Services.Client.Get(ObjectReference objectReference, String property)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.<>c__DisplayClass9_0`1.<GetInstanceProperty>b__0(IClient client)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.GetPropertyCore[T](JsiiPropertyAttribute propertyAttribute, Func`2 getFunc)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.GetInstanceProperty[T](String propertyName)
   at Amazon.CDK.AWS.Lambda.FunctionBase.get_FunctionName()
   at Serverless.Program.Main(String[] args) in /Users/nija/workplace/cdk/jsii-test-drive/dotnet/serverless/src/Serverless/Program.cs:line 36

[RomainMuller]

This is actually a duplicate of #240