Merge pull request #21454 from grpc/revert-21385-generic_unary

Revert "Generic API: assert when sending uninitialized byte buffer"

include/grpcpp/impl/codegen/byte_buffer.h

@@ -63,16 +63,13 @@ class DeserializeFuncType;
 class GrpcByteBufferPeer;
 
 }  // namespace internal
-/// A sequence of bytes. A ByteBuffer must be backed by at least one slice to be
-/// considered valid. You can consstruct an empty buffer through creating a
-/// ByteBuffer backed by one empty slice.
+/// A sequence of bytes.
 class ByteBuffer final {
  public:
-  /// Construct an uninitialized buffer.
+  /// Constuct an empty buffer.
   ByteBuffer() : buffer_(nullptr) {}
 
-  /// Construct buffer from \a slices, of which there are \a nslices. \a slices
-  /// must be a valid pointer.
+  /// Construct buffer from \a slices, of which there are \a nslices.
   ByteBuffer(const Slice* slices, size_t nslices) {
     // The following assertions check that the representation of a grpc::Slice
     // is identical to that of a grpc_slice:  it has a grpc_slice field, and

include/grpcpp/impl/codegen/call_op_set.h

@@ -310,12 +310,7 @@ class CallOpSendMessage {
 
  protected:
   void AddOp(grpc_op* ops, size_t* nops) {
-    if (msg_ == nullptr && !send_buf_.Valid()) {
-      // If SendMessage was called, this is an API misuse, since we're
-      // attempting to send an invalid message.
-      GPR_CODEGEN_DEBUG_ASSERT(!send_message_called_);
-      return;
-    }
+    if (msg_ == nullptr && !send_buf_.Valid()) return;
     if (hijacked_) {
       serializer_ = nullptr;
       return;
@@ -334,7 +329,6 @@ class CallOpSendMessage {
   }
   void FinishOp(bool* status) {
     if (msg_ == nullptr && !send_buf_.Valid()) return;
-    send_message_called_ = false;
     if (hijacked_ && failed_send_) {
       // Hijacking interceptor failed this Op
       *status = false;
@@ -375,7 +369,6 @@ class CallOpSendMessage {
   const void* msg_ = nullptr;  // The original non-serialized message
   bool hijacked_ = false;
   bool failed_send_ = false;
-  bool send_message_called_ = false;
   ByteBuffer send_buf_;
   WriteOptions write_options_;
   std::function<Status(const void*)> serializer_;
@@ -383,8 +376,6 @@ class CallOpSendMessage {
 
 template <class M>
 Status CallOpSendMessage::SendMessage(const M& message, WriteOptions options) {
-  GPR_CODEGEN_DEBUG_ASSERT(!send_message_called_);
-  send_message_called_ = true;
   write_options_ = options;
   serializer_ = [this](const void* message) {
     bool own_buf;