Rewind support seems broken

[kaibocai]

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We are working out the rewind support on durabletask-java, at microsoft/durabletask-java#123. In our end-to-end test, we found an exception thrown out (more details are microsoft/durabletask-java#123 (review)), to me this comes from the extension. Note that this exception is thrown out both using the POST HTTP request or using the client.rewind method.

Already had a quick chat with @jviau, it seems the extension drops the value that needed to be set in the grpc message somewhere.
I spent sometime look into the extension but with no luck on this due to lack of knowledge in extension, so open a issue here to track it.

I am open to have a session on this if it is preferred.

cc @davidmrdavid as well.

NOTE: JavaScript issues should be reported here: https://github.com/Azure/azure-functions-durable-js

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[kaibocai]

Related update on proto microsoft/durabletask-protobuf#18. Though, still need to find why reason is dropped.

[kaibocai]

With @davidmrdavid 's help, we debug into the extension and I found here

azure-functions-durable-extension/src/WebJobs.Extensions.DurableTask/Bindings/OrchestrationTriggerAttributeBindingProvider.cs

Lines 171 to 172 in 9f750eb

	PastEvents = { remoteContext.PastEvents.Select(ProtobufUtils.ToHistoryEventProto) },
	NewEvents = { remoteContext.NewEvents.Select(ProtobufUtils.ToHistoryEventProto) },

theremoteContext.PastEvents already contains a few GenericEvents that have null as value of Data, and that causing the exception in ProtobufUtils.ToHistoryEventProto. I am not quite sure where are those GenericEvents come from.

The GenericEvent created by rewind API seems in the remoteContext.newEvents and has the correct data set to rewind reason.

Also, I am told the logic for handling HTTP requests for java is totally different from js and python, java is using grpc while js and python is using HTTP. That may explain why I can run rewind successfully using js.

Hopefully the PR here microsoft/durabletask-protobuf#18 will have the issue resolved

cc @cgillum , @davidmrdavid , @jviau