Add onStreamPreReaped.

Summary: This is potentially useful to an application to know when the underlying stream state has been freed by the transport.

Reviewed By: jbeshay

Differential Revision: D52048888

fbshipit-source-id: e7b2d33c3702ce8aa348459a37094198d16af60f

quic/api/QuicSocket.h

@@ -131,6 +131,12 @@ class QuicSocket {
         StreamId,
         StreamGroupId) noexcept {}
 
+    /**
+     * Invoked when a given stream has been closed and its state reaped by
+     * the transport. After this point no operations can be done on the stream.
+     */
+    virtual void onStreamStateReaped(StreamId) noexcept {}
+
     /**
      * Invoked when a stream receives a StopSending frame from a peer.
      * The application should reset the stream as part of this callback.

quic/api/QuicTransportBase.cpp

@@ -2611,6 +2611,9 @@ void QuicTransportBase::checkForClosedStream() {
           getClosingStream(folly::to<std::string>(*itr)));
     }
     conn_->streamManager->removeClosedStream(*itr);
+    if (connCallback_) {
+      connCallback_->onStreamStateReaped(*itr);
+    }
     maybeSendStreamLimitUpdates(*conn_);
     if (readCbIt != readCallbacks_.end()) {
       readCallbacks_.erase(readCbIt);

quic/api/test/Mocks.h

@@ -123,6 +123,7 @@ class MockConnectionCallback : public QuicSocket::ConnectionCallback {
       onNewUnidirectionalStreamInGroup,
       (StreamId, StreamGroupId),
       (noexcept));
+  MOCK_METHOD((void), onStreamStateReaped, (StreamId), (noexcept));
   MOCK_METHOD(
       (void),
       onStopSending,

quic/api/test/QuicTransportBaseTest.cpp

@@ -1743,6 +1743,7 @@ TEST_P(QuicTransportImplTestBase, CloseStreamAfterReadError) {
   transport->closeStream(stream1);
 
   EXPECT_CALL(readCb1, readError(stream1, IsError(LocalErrorCode::NO_ERROR)));
+  EXPECT_CALL(connCallback, onStreamStateReaped(stream1));
   transport->driveReadCallbacks();
 
   EXPECT_FALSE(transport->transportConn->streamManager->streamExists(stream1));