fix onBidirectionalStreamsAvailable

Summary:
fixes the arg passed to the ::onBidirectionalStreamsAvailable callback

#facebook:
i accidentally introduced a bad operator precedence bug in a refactor; this fixes that and the unit test

luckily HQSession doesn't consume the argument passed to the callback

Reviewed By: knekritz

Differential Revision: D62765762

fbshipit-source-id: 7ae206d5036fc744485736f92fd366ce99103d58

quic/api/QuicTransportBase.cpp

@@ -1064,15 +1064,17 @@ void QuicTransportBase::invokeStreamsAvailableCallbacks() {
   if (conn_->streamManager->consumeMaxLocalBidirectionalStreamIdIncreased()) {
     // check in case new streams were created in preceding callbacks
     // and max is already reached
-    if (auto numStreams = getNumOpenableBidirectionalStreams() > 0) {
-      connCallback_->onBidirectionalStreamsAvailable(numStreams);
+    auto numOpenableStreams = getNumOpenableBidirectionalStreams();
+    if (numOpenableStreams > 0) {
+      connCallback_->onBidirectionalStreamsAvailable(numOpenableStreams);
     }
   }
   if (conn_->streamManager->consumeMaxLocalUnidirectionalStreamIdIncreased()) {
     // check in case new streams were created in preceding callbacks
     // and max is already reached
-    if (auto numStreams = getNumOpenableUnidirectionalStreams() > 0) {
-      connCallback_->onUnidirectionalStreamsAvailable(numStreams);
+    auto numOpenableStreams = getNumOpenableUnidirectionalStreams();
+    if (numOpenableStreams > 0) {
+      connCallback_->onUnidirectionalStreamsAvailable(numOpenableStreams);
     }
   }
 }

quic/api/test/QuicTransportBaseTest.cpp

@@ -1636,13 +1636,15 @@ TEST_P(QuicTransportImplTestBase, onBidiStreamsAvailableCallback) {
 
   EXPECT_CALL(connCallback, onBidirectionalStreamsAvailable(_))
       .WillOnce(Invoke([](uint64_t numAvailableStreams) {
-        EXPECT_EQ(numAvailableStreams, 1);
+        EXPECT_EQ(numAvailableStreams, 10);
       }));
-  transport->addMaxStreamsFrame(MaxStreamsFrame(1, /*isBidirectionalIn=*/true));
-  EXPECT_EQ(transport->getNumOpenableBidirectionalStreams(), 1);
+  transport->addMaxStreamsFrame(
+      MaxStreamsFrame(10, /*isBidirectionalIn=*/true));
+  EXPECT_EQ(transport->getNumOpenableBidirectionalStreams(), 10);
 
   // same value max streams frame doesn't trigger callback
-  transport->addMaxStreamsFrame(MaxStreamsFrame(1, /*isBidirectionalIn=*/true));
+  transport->addMaxStreamsFrame(
+      MaxStreamsFrame(10, /*isBidirectionalIn=*/true));
 }
 
 TEST_P(QuicTransportImplTestBase, onBidiStreamsAvailableCallbackAfterExausted) {