IProgress Callee Registration Fails on Xamarin.Android

[StevenBonePgh]

When registering a reflection-based callee with an IProgress parameter on Xamarin.Android an index out of range exception is thrown. This worked in 18.3.2, I first noticed it broken in 18.8.2, and it remains broken in 18.8.5. On .NET 4.7.1 and Xamarin.UWP the callee registers just fine. I do not have a Mac to check that platform, sorry.

The interface method likely causing the issue looks like this:

[WampProcedure("my.getfoo")]
[WampProgressiveResultProcedure]
Task<FooChunk> GetFooAsync(string fooName, IProgress<FooChunk> progress);

The exception happens when calling Channel.RealmProxy.Services.RegisterCallee with the object implementing that interface.

{System.IndexOutOfRangeException} "Index was outside the bounds of the array."
  at System.Attribute.InternalParamIsDefined (System.Reflection.ParameterInfo parameter, System.Type attributeType, System.Boolean inherit) [0x0003b] in <43dbbdc147f2482093d8409abb04c233>:0 
  at System.Attribute.IsDefined (System.Reflection.ParameterInfo element, System.Type attributeType, System.Boolean inherit) [0x00071] in <43dbbdc147f2482093d8409abb04c233>:0 
  at System.Attribute.IsDefined (System.Reflection.ParameterInfo element, System.Type attributeType) [0x00000] in <43dbbdc147f2482093d8409abb04c233>:0 
  at System.Reflection.CustomAttributeExtensions.IsDefined (System.Reflection.ParameterInfo element, System.Type attributeType) [0x00000] in <43dbbdc147f2482093d8409abb04c233>:0 
  at WampSharp.V2.Rpc.MethodInfoValidation.ValidateTupleReturnTypeOfProgressiveMethod (System.Reflection.MethodInfo method, System.Reflection.ParameterInfo lastParameter) [0x00000] in D:\a\1\s\src\net45\WampSharp\WAMP2\V2\Rpc\Callee\Reflection\MethodInfoValidation.cs:126 
  at WampSharp.V2.Rpc.MethodInfoValidation.ValidateProgressiveMethod (System.Reflection.MethodInfo method) [0x00081] in D:\a\1\s\src\net45\WampSharp\WAMP2\V2\Rpc\Callee\Reflection\MethodInfoValidation.cs:121 
  at WampSharp.V2.Rpc.OperationExtractor.CreateRpcMethod (System.Func`1[TResult] instanceProvider, WampSharp.V2.ICalleeRegistrationInterceptor interceptor, System.Reflection.MethodInfo method) [0x00040] in D:\a\1\s\src\net45\WampSharp\WAMP2\V2\Rpc\Callee\Reflection\OperationExtractor.cs:69 
  at WampSharp.V2.Rpc.OperationExtractor+<GetServiceMethodsOfType>d__2.MoveNext () [0x00060] in D:\a\1\s\src\net45\WampSharp\WAMP2\V2\Rpc\Callee\Reflection\OperationExtractor.cs:47 
  at WampSharp.V2.Rpc.OperationExtractor+<ExtractOperations>d__0.MoveNext () [0x000aa] in D:\a\1\s\src\net45\WampSharp\WAMP2\V2\Rpc\Callee\Reflection\OperationExtractor.cs:21 
  at WampSharp.V2.WampRealmProxyServiceProvider.RegisterCallee (System.Type type, System.Func`1[TResult] instanceProvider, WampSharp.V2.ICalleeRegistrationInterceptor interceptor) [0x00047] in D:\a\1\s\src\net45\WampSharp\WAMP2\V2\Api\Client\WampRealmProxyServiceProvider.cs:70 
  at WampSharp.V2.WampRealmProxyServiceProvider.RegisterCallee (System.Object instance, WampSharp.V2.ICalleeRegistrationInterceptor interceptor) [0x0000d] in D:\a\1\s\src\net45\WampSharp\WAMP2\V2\Api\Client\WampRealmProxyServiceProvider.cs:39 

I have a CalleeRegistrationInterceptor, and right after it calls GetProcedureUri for the method in question is when the exception is thrown, which is why I suspect the above procedure is the guilty party. There seems to have been a large code churn in the areas in the call stack from when I confirmed it worked, but in a quick glance it was not obvious to me where the issue happens to be. Any ideas? I can try to nail it down further Monday if need be.

Thanks, Elad!

[darkl]

I guess that method.ReturnParameter may return null on Xamarin.Android. Maybe you can verify this. Thanks Elad

[darkl]

Ok, let's look at mono's InternalParamIsDefined implementation. I guess that when the ParameterInfo is method.ReturnParameter, the parameter.Position is negative/too large, and therefore we get the IndexOutOfRangeException. I find it weird that this worked in a previous version. Maybe I changed the dependencies and it affected Xamarin.Android somehow.

Elad

[darkl]

So WampSharp uses ReturnParameter in a couple of more places, some run very often (the method HasMultivaluedResult). The difference between the calls is that in ValidateTupleReturnTypeOfProgressiveMethod , IsDefined is used, and in the other places GetCustomAttribute<> is used. This is probably a bug in mono, which we should file. Anyway, this can be addressed by replacing IsDefined with GetCustomAttribute<> , and checking that the attribute is not null. Usually after calling IsDefined, GetCustomAttribute<> is called, so this might make the code actually a bit shorter.

[StevenBonePgh]

I created a Xamarin Android Unit test project and linked all existing WampSharp.Tests.Wampv2 tests to it. Result is 13 or 14 failures, Making the suggested changes to 4 methods where ReturnParameter.IsDefined was used and replacing it with GetCustomAttribute<> resolves all unit test failures.

src\net45\WampSharp\WAMP2\V2\Rpc\Callee\Reflection\ResultExtractor\WampResultExtractor.cs:
    GetValueTupleResultExtractor
src\net45\WampSharp\WAMP2\V2\Rpc\Callee\Reflection\MethodInfoValidation.cs:
    ValidateTupleReturnType and ValidateTupleReturnTypeOfProgressiveMethod
src\net45\WampSharp\WAMP2\V2\Api\CalleeProxy\Callbacks\Async\OperationResultExtractor.cs:
    GetTupleArgumentUnpacker 

I created an archive with these changes and the Xamarin.Android nunit runner (I included log4net and appenders that append to the nunit log and the android logger). I included the test project in the WampSharpNetStandard.sln for my purposes. If you'd like me to add this to a PR, I'd appreciate guidance as to a proper location, but feel free to take the archive and locate it wherever you desire.

WampSharp_Resolve268.zip

I'll attempt to create a simple repro to send to Mono. To be honest, I have no idea where to report these things with Xamarin, as some are Xamarin, some are Mono, and some are Mono-[Platform].

[darkl]

I think you can report this bug here, see this page.

Just to clarify: the bug is with the usage of method.ReturnParameter.IsDefined.

Elad

[darkl]

I merged your changes, excluding the unit tests. If everything works out, v18.9.1 should be published on NuGet soon. I opened issue #269. Will be done some time in the future.

[StevenBonePgh]

Just to clarify: the bug is with the usage of method.ReturnParameter.IsDefined.

Correct, that was the issue. I confirmed that 18.9.1 resolves this issue. Thanks for the assist here. It could be a recent break in Xamarin/Mono, as I also believe that I was working with an earlier version when it was working (the WampSharp version change was likely not the only change between working/nonworking).

[darkl]

@StevenBonePgh, can you please file a bug to mono?