[orc-rt] Add transparent SPS conversion for error/expected types.

This commit aims to reduce boilerplate by adding transparent conversion between
Error/Expected types and their SPS-serializable counterparts
(SPSSerializableError/SPSSerializableExpected). This allows SPSWrapperFunction
calls and handles to be written in terms of Error/Expected directly.

This functionality can also be extended to transparently convert between other
types. This may be used in the future to provide conversion between
ExecutorAddr and native pointer types.

Author: lhames

orc-rt/include/orc-rt/SPSWrapperFunction.h

@@ -21,8 +21,10 @@ namespace orc_rt {
 namespace detail {
 
 template <typename... SPSArgTs> struct WFSPSHelper {
-  template <typename... ArgTs>
-  std::optional<WrapperFunctionBuffer> serialize(const ArgTs &...Args) {
+private:
+  template <typename... SerializableArgTs>
+  std::optional<WrapperFunctionBuffer>
+  serializeImpl(const SerializableArgTs &...Args) {
     auto R =
         WrapperFunctionBuffer::allocate(SPSArgList<SPSArgTs...>::size(Args...));
     SPSOutputBuffer OB(R.data(), R.size());
@@ -31,16 +33,61 @@ template <typename... SPSArgTs> struct WFSPSHelper {
     return std::move(R);
   }
 
+  template <typename T> static const T &toSerializable(const T &Arg) noexcept {
+    return Arg;
+  }
+
+  static SPSSerializableError toSerializable(Error Err) noexcept {
+    return SPSSerializableError(std::move(Err));
+  }
+
+  template <typename T>
+  static SPSSerializableExpected<T> toSerializable(Expected<T> Arg) noexcept {
+    return SPSSerializableExpected<T>(std::move(Arg));
+  }
+
+  template <typename... Ts> struct DeserializableTuple;
+
+  template <typename... Ts> struct DeserializableTuple<std::tuple<Ts...>> {
+    typedef std::tuple<
+        std::decay_t<decltype(toSerializable(std::declval<Ts>()))>...>
+        type;
+  };
+
+  template <typename... Ts>
+  using DeserializableTuple_t = typename DeserializableTuple<Ts...>::type;
+
+  template <typename T> static T fromSerializable(T &&Arg) noexcept {
+    return Arg;
+  }
+
+  static Error fromSerializable(SPSSerializableError Err) noexcept {
+    return Err.toError();
+  }
+
+  template <typename T>
+  static Expected<T> fromSerializable(SPSSerializableExpected<T> Val) noexcept {
+    return Val.toExpected();
+  }
+
+public:
+  template <typename... ArgTs>
+  std::optional<WrapperFunctionBuffer> serialize(ArgTs &&...Args) {
+    return serializeImpl(toSerializable(std::forward<ArgTs>(Args))...);
+  }
+
   template <typename ArgTuple>
   std::optional<ArgTuple> deserialize(WrapperFunctionBuffer ArgBytes) {
     assert(!ArgBytes.getOutOfBandError() &&
            "Should not attempt to deserialize out-of-band error");
     SPSInputBuffer IB(ArgBytes.data(), ArgBytes.size());
-    ArgTuple Args;
-    if (!SPSSerializationTraits<SPSTuple<SPSArgTs...>, ArgTuple>::deserialize(
-            IB, Args))
+    DeserializableTuple_t<ArgTuple> Args;
+    if (!SPSSerializationTraits<SPSTuple<SPSArgTs...>,
+                                decltype(Args)>::deserialize(IB, Args))
       return std::nullopt;
-    return Args;
+    return std::apply(
+        [](auto &&...A) { return ArgTuple(fromSerializable(A)...); },
+        std::move(Args));
   }
 };
 

orc-rt/include/orc-rt/WrapperFunction.h

@@ -168,7 +168,8 @@ struct ResultDeserializer<std::tuple<Expected<T>>, Serializer> {
                                  Serializer &S) {
     if (auto Val = S.result().template deserialize<std::tuple<T>>(
             std::move(ResultBytes)))
-      return std::move(std::get<0>(*Val));
+      return Expected<T>(std::move(std::get<0>(*Val)),
+                         ForceExpectedSuccessValue());
     else
       return make_error<StringError>("Could not deserialize result");
   }

orc-rt/unittests/SPSWrapperFunctionTest.cpp

@@ -144,3 +144,77 @@ TEST(SPSWrapperFunctionUtilsTest, TestBinaryOpViaFunctionPointer) {
       [&](Expected<int32_t> R) { Result = cantFail(std::move(R)); }, 41, 1);
   EXPECT_EQ(Result, 42);
 }
+
+static void improbable_feat_sps_wrapper(orc_rt_SessionRef Session,
+                                        void *CallCtx,
+                                        orc_rt_WrapperFunctionReturn Return,
+                                        orc_rt_WrapperFunctionBuffer ArgBytes) {
+  SPSWrapperFunction<SPSError(bool)>::handle(
+      Session, CallCtx, Return, ArgBytes,
+      [](move_only_function<void(Error)> Return, bool LuckyHat) {
+        if (LuckyHat)
+          Return(Error::success());
+        else
+          Return(make_error<StringError>("crushed by boulder"));
+      });
+}
+
+TEST(SPSWrapperFunctionUtilsTest, TestFunctionReturningErrorSuccessCase) {
+  bool DidRun = false;
+  SPSWrapperFunction<SPSError(bool)>::call(
+      DirectCaller(nullptr, improbable_feat_sps_wrapper),
+      [&](Expected<Error> E) {
+        DidRun = true;
+        cantFail(cantFail(std::move(E)));
+      },
+      true);
+
+  EXPECT_TRUE(DidRun);
+}
+
+TEST(SPSWrapperFunctionUtilsTest, TestFunctionReturningErrorFailureCase) {
+  std::string ErrMsg;
+  SPSWrapperFunction<SPSError(bool)>::call(
+      DirectCaller(nullptr, improbable_feat_sps_wrapper),
+      [&](Expected<Error> E) { ErrMsg = toString(cantFail(std::move(E))); },
+      false);
+
+  EXPECT_EQ(ErrMsg, "crushed by boulder");
+}
+
+static void halve_number_sps_wrapper(orc_rt_SessionRef Session, void *CallCtx,
+                                     orc_rt_WrapperFunctionReturn Return,
+                                     orc_rt_WrapperFunctionBuffer ArgBytes) {
+  SPSWrapperFunction<SPSExpected<int32_t>(int32_t)>::handle(
+      Session, CallCtx, Return, ArgBytes,
+      [](move_only_function<void(Expected<int32_t>)> Return, int N) {
+        if (N % 2 == 0)
+          Return(N >> 1);
+        else
+          Return(make_error<StringError>("N is not a multiple of 2"));
+      });
+}
+
+TEST(SPSWrapperFunctionUtilsTest, TestFunctionReturningExpectedSuccessCase) {
+  int32_t Result = 0;
+  SPSWrapperFunction<SPSExpected<int32_t>(int32_t)>::call(
+      DirectCaller(nullptr, halve_number_sps_wrapper),
+      [&](Expected<Expected<int32_t>> R) {
+        Result = cantFail(cantFail(std::move(R)));
+      },
+      2);
+
+  EXPECT_EQ(Result, 1);
+}
+
+TEST(SPSWrapperFunctionUtilsTest, TestFunctionReturningExpectedFailureCase) {
+  std::string ErrMsg;
+  SPSWrapperFunction<SPSExpected<int32_t>(int32_t)>::call(
+      DirectCaller(nullptr, halve_number_sps_wrapper),
+      [&](Expected<Expected<int32_t>> R) {
+        ErrMsg = toString(cantFail(std::move(R)).takeError());
+      },
+      3);
+
+  EXPECT_EQ(ErrMsg, "N is not a multiple of 2");
+}