Failed bindig in MethodDelegation due to return type mismatch

[ceki]

UPDATE: The problem has been simplified to providing the source method name to the target of MethodCall (see comment below)

UPDATE 2: I have reverted to trying to use MethodDelegation instead of MethodCall. Moreover, using @Pipe annotation seems to make a difference. See the vehicle2 package in the project. It looks like I have found a working solution to my problem.

Hello,

I am trying to put in place support for API extensions via user defined interfaces.

The source code for the problem at hand can be found at https://github.com/ceki/vehicle

Running the VehicleMain results in a IllegalArgumentException (see below).

However, the IllegalArgumentException disappears if the return type of generate method in TigthenBoltsGenerator is changed from <E extends Engine> to UserDefinedEngine.

How can I convince ByteBuddy that the generate method is compatible with
ch.qos.vehicle.UserDefinedEngine.tightenBolts() even if the return values do not match exactly?

Here is the exception:

Exception in thread "main" java.lang.IllegalArgumentException: None of [public static ch.qos.vehicle.Engine ch.qos.vehicle.TigthenBoltsGenerator.generate(ch.qos.vehicle.Engine,java.lang.reflect.Method)] allows for delegation from public abstract ch.qos.vehicle.UserDefinedEngine ch.qos.vehicle.UserDefinedEngine.tightenBolts()
	at net.bytebuddy.implementation.bind.MethodDelegationBinder$Processor.bind(MethodDelegationBinder.java:1099)
	at net.bytebuddy.implementation.MethodDelegation$Appender.apply(MethodDelegation.java:1349)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyCode(TypeWriter.java:730)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod$WithBody.applyBody(TypeWriter.java:715)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$MethodPool$Record$ForDefinedMethod.apply(TypeWriter.java:622)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$Default$ForCreation.create(TypeWriter.java:6043)
	at net.bytebuddy.dynamic.scaffold.TypeWriter$Default.make(TypeWriter.java:2224)
	at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$UsingTypeWriter.make(DynamicType.java:4055)
	at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:3739)
	at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$Delegator.make(DynamicType.java:3991)
	at ch.qos.vehicle.GetEngineDelegation.generate(GetEngineDelegation.java:28)
	at ch.qos.vehicle.VehicleBase$ByteBuddy$3nHQC6jP.getEngine(Unknown Source)
	at ch.qos.vehicle.VehicleBase$ByteBuddy$3nHQC6jP.getEngine(Unknown Source)
	at ch.qos.vehicle.VehicleMain.main(VehicleMain.java:18)

Can you point me in the right direction please?

[ceki]

After further research, MethodCall seems preferable to MethodDelegation for my use case.

One remaining hurdle is how to pass the source method name to the target. When using MethodDelegation, declaring a @Origin Method sourceMethod parameter did the trick. However, I was not yet able to find a way to pass the source method name with MethodCall.

[raphw]

I think you can add @RuntimeType to the method. There is no way to statically verify the MethodDelegation's assignment, so with that annotation Byte Buddy attemps a runtime cast. From what I saw delegation looks like the right approach.

[ceki]

@raphw I thought I had already added the @RuntimeType annotation. I will check and get back here.

[ceki]

@raphw Indeed, the @RuntimeType annotation does the trick. Thank you.