Fix inconsistent invocation of MoqtResponseCallback.

When an application initiates a request via MoqtSessionInterface, a return of false or nullptr indicates that the request was never sent due to a variety of local restrictions. After discussing with @vasilvv, these cases should not invoke the provided MoqtResponseCallback.

Not in production.

PiperOrigin-RevId: 963545134

quiche/quic/moqt/moqt_session.cc

diff --git a/quiche/quic/moqt/moqt_session.cc b/quiche/quic/moqt/moqt_session.cc
index 753e5ba..4b7c3a6 100644
--- a/quiche/quic/moqt/moqt_session.cc
+++ b/quiche/quic/moqt/moqt_session.cc
@@ -296,9 +296,6 @@
     return nullptr;
   }
   if (!outgoing_subscribe_namespace_.SubscribeNamespace(prefix)) {
-    std::move(response_callback)(MoqtRequestErrorInfo{
-        RequestErrorCode::kInternalError, std::nullopt,
-        "SUBSCRIBE_NAMESPACE already outstanding for namespace"});
     return nullptr;
   }
   std::unique_ptr<MoqtSubscribeNamespaceRequestStream> state =
@@ -353,16 +350,11 @@
   QUICHE_DCHECK(name.IsValid());
   if (received_goaway_ || sent_goaway_) {
     QUIC_DLOG(INFO) << ENDPOINT << "Tried to send TRACK_STATUS after GOAWAY";
-    std::move(response_callback)(MoqtRequestErrorInfo{
-        RequestErrorCode::kGoingAway, std::nullopt, "GOAWAY received"});
     return false;
   }
 
   webtransport::Stream* stream = session_->OpenOutgoingBidirectionalStream();
   if (stream == nullptr) {
-    std::move(response_callback)(
-        MoqtRequestErrorInfo{RequestErrorCode::kInternalError, std::nullopt,
-                             "Flow control blocked"});
     return false;
   }
 

quiche/quic/moqt/moqt_session_interface.h

diff --git a/quiche/quic/moqt/moqt_session_interface.h b/quiche/quic/moqt/moqt_session_interface.h
index 4d0801e..1af02d8 100644
--- a/quiche/quic/moqt/moqt_session_interface.h
+++ b/quiche/quic/moqt/moqt_session_interface.h
@@ -96,6 +96,12 @@
   // Close the session with a fatal error.
   virtual void Error(MoqtError code, absl::string_view error) = 0;
 
+  // Many of these functions initiate a request and take MoqtResponseCallback to
+  // report the peer's response. These functions return false if there is an
+  // immediate problem that prevents sending the request, in which case the
+  // callback will not be invoked. For example, there might not be stream credit
+  // to open a request stream, or the request is a duplicate, or the session
+  // is in a GOAWAY state.
   // Return true if SUBSCRIBE was actually sent.
   virtual bool Subscribe(const FullTrackName& name,
                          SubscribeVisitor* absl_nonnull visitor,
@@ -188,7 +194,7 @@
 
   // Sends TRACK_STATUS request to the peer. Returns `false` if the request
   // immediately fails (usually due to flow control), and `true` otherwise;
-  // `response_callback` will be eventually invoked in either case.
+  // `response_callback` will be eventually invoked if true.
   virtual bool TrackStatus(const FullTrackName& name,
                            const MessageParameters& parameters,
                            MoqtResponseCallback response_callback) = 0;