Allow deserialize during cursor read

Summary: There's nothing wrong with concurrent reads where only one needs access to cursor state.

Reviewed By: Mizuchi

Differential Revision: D66831490

fbshipit-source-id: c6d38adb0a8ab6cc74b43ff4ea719389d0763347

third-party/thrift/src/thrift/lib/cpp2/protocol/CursorBasedSerializer.h

@@ -17,11 +17,11 @@
 #pragma once
 
 #include <algorithm>
-#include <initializer_list>
 #include <variant>
 #include <folly/io/Cursor.h>
 #include <folly/io/IOBufQueue.h>
 #include <thrift/lib/cpp2/protocol/BinaryProtocol.h>
+#include <thrift/lib/cpp2/protocol/Serializer.h>
 #include <thrift/lib/cpp2/protocol/detail/CursorBasedSerialization.h>
 #include <thrift/lib/cpp2/type/NativeType.h>
 #include <thrift/lib/cpp2/type/ThriftType.h>
@@ -70,6 +70,7 @@ class CursorSerializationWrapper {
   static_assert(
       std::is_same_v<ProtocolWriter, BinaryProtocolWriter>,
       "ProtocolWriter must be BinaryProtocolReader");
+  using Serializer = Serializer<ProtocolReader, ProtocolWriter>;
 
  public:
   CursorSerializationWrapper() = default;
@@ -100,12 +101,13 @@ class CursorSerializationWrapper {
    * Object read path (traditional Thrift deserialization)
    * Deserializes into a (returned) Thrift object.
    */
-  T deserialize() {
+  T deserialize() const {
+    if (std::holds_alternative<ProtocolWriter>(protocol_)) {
+      folly::throw_exception<std::runtime_error>(
+          "Concurrent reads/writes not supported");
+    }
     checkHasData();
-    T ret;
-    ret.read(reader());
-    done();
-    return ret;
+    return Serializer::template deserialize<T>(serializedData_.get());
   }
 
   /**

third-party/thrift/src/thrift/lib/cpp2/protocol/test/CursorBasedSerializerTest.cpp

@@ -16,7 +16,6 @@
 
 #include <thrift/lib/cpp2/protocol/CursorBasedSerializer.h>
 
-#include <ranges>
 #include <folly/portability/GMock.h>
 #include <folly/portability/GTest.h>
 #include <thrift/lib/cpp2/protocol/test/gen-cpp2/cursor_clients.h>
@@ -686,3 +685,18 @@ TEST(CursorBasedSerializer, CursorReadRemainingEndOne) {
 TEST(CursorBasedSerializer, CursorReadRemainingEndMany) {
   doCursorReadRemainEndTest(10);
 }
+
+TEST(CursorBasedSerializer, ConcurrentAccess) {
+  EmptyWrapper wrapper;
+  auto writer = wrapper.beginWrite();
+  EXPECT_THROW(wrapper.beginRead(), std::runtime_error);
+  EXPECT_THROW(wrapper.deserialize(), std::runtime_error);
+  EXPECT_THROW(wrapper.beginWrite(), std::runtime_error);
+  wrapper.endWrite(std::move(writer));
+
+  auto reader = wrapper.beginRead();
+  EXPECT_THROW(wrapper.beginRead(), std::runtime_error);
+  EXPECT_EQ(wrapper.deserialize(), Empty{});
+  EXPECT_THROW(wrapper.beginWrite(), std::runtime_error);
+  wrapper.endRead(std::move(reader));
+}