Re-enable public constructor for ClientAsyncResponseReader to avoid busting...

Re-enable public constructor for ClientAsyncResponseReader to avoid busting client that bypassed code generator. This code is deprecated-on-arrival as it is a performance pessimization. This code path should not be used.

include/grpc++/impl/codegen/async_unary_call.h

@@ -87,6 +87,28 @@ class ClientAsyncResponseReader final
         ClientAsyncResponseReader(call, context, request);
   }
 
+  /// TODO(vjpai): Delete the below constructor
+  /// PLEASE DO NOT USE THIS CONSTRUCTOR IN NEW CODE
+  /// This code is only present as a short-term workaround
+  /// for users that bypassed the code-generator and directly
+  /// created this struct rather than properly using a stub.
+  /// This code will not remain a valid public constructor for long.
+  template <class W>
+  ClientAsyncResponseReader(ChannelInterface* channel, CompletionQueue* cq,
+                            const RpcMethod& method, ClientContext* context,
+                            const W& request)
+      : context_(context),
+        call_(channel->CreateCall(method, context, cq)),
+        collection_(std::make_shared<Ops>()) {
+    collection_->init_buf_.SetCollection(collection_);
+    collection_->init_buf_.SendInitialMetadata(
+        context->send_initial_metadata_, context->initial_metadata_flags());
+    // TODO(ctiller): don't assert
+    GPR_CODEGEN_ASSERT(collection_->init_buf_.SendMessage(request).ok());
+    collection_->init_buf_.ClientSendClose();
+    call_.PerformOps(&collection_->init_buf_);
+  }
+
   // always allocated against a call arena, no memory free required
   static void operator delete(void* ptr, std::size_t size) {
     assert(size == sizeof(ClientAsyncResponseReader));
@@ -101,9 +123,18 @@ class ClientAsyncResponseReader final
   void ReadInitialMetadata(void* tag) {
     GPR_CODEGEN_ASSERT(!context_->initial_metadata_received_);
 
-    meta_buf_.set_output_tag(tag);
-    meta_buf_.RecvInitialMetadata(context_);
-    call_.PerformOps(&meta_buf_);
+    Ops& o = ops;
+
+    // TODO(vjpai): Remove the collection_ specialization as soon
+    // as the public constructor is deleted
+    if (collection_) {
+      o = *collection_;
+      collection_->meta_buf_.SetCollection(collection_);
+    }
+
+    o.meta_buf_.set_output_tag(tag);
+    o.meta_buf_.RecvInitialMetadata(context_);
+    call_.PerformOps(&o.meta_buf_);
   }
 
   /// See \a ClientAysncResponseReaderInterface::Finish for semantics.
@@ -112,14 +143,23 @@ class ClientAsyncResponseReader final
   ///   - the \a ClientContext associated with this call is updated with
   ///     possible initial and trailing metadata sent from the server.
   void Finish(R* msg, Status* status, void* tag) {
-    finish_buf_.set_output_tag(tag);
+    Ops& o = ops;
+
+    // TODO(vjpai): Remove the collection_ specialization as soon
+    // as the public constructor is deleted
+    if (collection_) {
+      o = *collection_;
+      collection_->finish_buf_.SetCollection(collection_);
+    }
+
+    o.finish_buf_.set_output_tag(tag);
     if (!context_->initial_metadata_received_) {
-      finish_buf_.RecvInitialMetadata(context_);
+      o.finish_buf_.RecvInitialMetadata(context_);
     }
-    finish_buf_.RecvMessage(msg);
-    finish_buf_.AllowNoMessage();
-    finish_buf_.ClientRecvStatus(context_, status);
-    call_.PerformOps(&finish_buf_);
+    o.finish_buf_.RecvMessage(msg);
+    o.finish_buf_.AllowNoMessage();
+    o.finish_buf_.ClientRecvStatus(context_, status);
+    call_.PerformOps(&o.finish_buf_);
   }
 
  private:
@@ -129,25 +169,33 @@ class ClientAsyncResponseReader final
   template <class W>
   ClientAsyncResponseReader(Call call, ClientContext* context, const W& request)
       : context_(context), call_(call) {
-    init_buf_.SendInitialMetadata(context->send_initial_metadata_,
-                                  context->initial_metadata_flags());
+    ops.init_buf_.SendInitialMetadata(context->send_initial_metadata_,
+                                      context->initial_metadata_flags());
     // TODO(ctiller): don't assert
-    GPR_CODEGEN_ASSERT(init_buf_.SendMessage(request).ok());
-    init_buf_.ClientSendClose();
-    call_.PerformOps(&init_buf_);
+    GPR_CODEGEN_ASSERT(ops.init_buf_.SendMessage(request).ok());
+    ops.init_buf_.ClientSendClose();
+    call_.PerformOps(&ops.init_buf_);
   }
 
   // disable operator new
   static void* operator new(std::size_t size);
   static void* operator new(std::size_t size, void* p) { return p; }
 
-  SneakyCallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
-                  CallOpClientSendClose>
-      init_buf_;
-  CallOpSet<CallOpRecvInitialMetadata> meta_buf_;
-  CallOpSet<CallOpRecvInitialMetadata, CallOpRecvMessage<R>,
-            CallOpClientRecvStatus>
-      finish_buf_;
+  // TODO(vjpai): Remove the reference to CallOpSetCollectionInterface
+  // as soon as the related workaround (public constructor) is deleted
+  struct Ops : public CallOpSetCollectionInterface {
+    SneakyCallOpSet<CallOpSendInitialMetadata, CallOpSendMessage,
+                    CallOpClientSendClose>
+        init_buf_;
+    CallOpSet<CallOpRecvInitialMetadata> meta_buf_;
+    CallOpSet<CallOpRecvInitialMetadata, CallOpRecvMessage<R>,
+              CallOpClientRecvStatus>
+        finish_buf_;
+  } ops;
+
+  // TODO(vjpai): Remove the collection_ as soon as the related workaround
+  // (public constructor) is deleted
+  std::shared_ptr<Ops> collection_;
 };
 
 /// Async server-side API for handling unary calls, where the single

include/grpc++/impl/codegen/call.h

@@ -544,6 +544,11 @@ class CallOpClientRecvStatus {
   grpc_slice error_message_;
 };
 
+/// TODO(vjpai): Remove the existence of CallOpSetCollectionInterface
+/// and references to it. This code is deprecated-on-arrival and is
+/// only added for users that bypassed the code-generator.
+class CallOpSetCollectionInterface {};
+
 /// An abstract collection of call ops, used to generate the
 /// grpc_call_op structure to pass down to the lower layers,
 /// and as it is-a CompletionQueueTag, also massages the final
@@ -554,6 +559,18 @@ class CallOpSetInterface : public CompletionQueueTag {
   /// Fills in grpc_op, starting from ops[*nops] and moving
   /// upwards.
   virtual void FillOps(grpc_call* call, grpc_op* ops, size_t* nops) = 0;
+
+  /// TODO(vjpai): Remove the SetCollection method and comment. This is only
+  /// a short-term workaround for users that bypassed the code generator
+  /// Mark this as belonging to a collection if needed
+  void SetCollection(std::shared_ptr<CallOpSetCollectionInterface> collection) {
+    collection_ = collection;
+  }
+
+ protected:
+  /// TODO(vjpai): Remove the collection_ field once the idea of bypassing the
+  /// code generator is forbidden. This is already deprecated
+  std::shared_ptr<CallOpSetCollectionInterface> collection_;
 };
 
 /// Primary implementaiton of CallOpSetInterface.
@@ -594,6 +611,9 @@ class CallOpSet : public CallOpSetInterface,
     this->Op6::FinishOp(status);
     *tag = return_tag_;
     g_core_codegen_interface->grpc_call_unref(call_);
+    // TODO(vjpai): Remove the reference to collection_ once the idea of
+    // bypassing the code generator is forbidden. It is already deprecated
+    collection_.reset();
     return true;
   }