[capnproto] Recursive autoReconnect logic

[Vaci]

I'm trying to add reconnection behaviour to capabilities with 
autoReconnect, but the behaviour isn't what I'd expect when I have multiple 
levels of reconnecting capabilities that are pipelined:

Given a trivial schema that obtains one capability from another:

reconnect-test.capnp:
@0xa0fdcabdd0230110;
interface TestB {
  getA @0 () -> (a : Capability);
}

This example code deliberately creates capability B as disconnected, so I'd 
expect an attempt to reconnect the B capability, but instead, only 
reconnection of the A capability is attempted:

reconnect-test.cpp:
#include "reconnect-test.capnp.h"
#include <capnp/reconnect.h>
#include <kj/main.h>
#include <kj/async.h>
#include <kj/debug.h>

int main(int argc, char* argv[]) {
  kj::EventLoop loop;
  kj::WaitScope waitScope{loop};

  auto b = capnp::autoReconnect([&](){
    KJ_LOG(WARNING, "Reconnecting B");
    return TestB::Client{KJ_EXCEPTION(DISCONNECTED)};
  });

  auto a = capnp::autoReconnect([&]{
    KJ_LOG(WARNING, "Reconnecting A");
    return b.getARequest().send().getA();
  });

  try {
    a.typelessRequest(0, 0, nullptr).send().wait(waitScope);
  }
  catch (kj::Exception& exc) {
    KJ_LOG(ERROR, "1", exc);
  }

  try {
    a.typelessRequest(0, 0, nullptr).send().wait(waitScope);
  }
  catch (kj::Exception& exc) {
    KJ_LOG(ERROR, "2", exc);
  }
}

Output:
reconnect-test.cpp:12: warning: Reconnecting B
reconnect-test.cpp:17: warning: Reconnecting A
reconnect-test.cpp:17: warning: Reconnecting A
reconnect-test.cpp:25: error: 1; exc = reconnect-test.cpp:13: disconnected
reconnect-test.cpp:17: warning: Reconnecting A
reconnect-test.cpp:32: error: 2; exc = reconnect-test.cpp:13: disconnected

I'd expect the second attempt to result in a reconnection of the broken 
capability B when the (eventual) call to getARequest() occurs?

If I remove the pipelining, and force the call to getARequest to complete, 
then B reconnects just fine.

Vaci

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