Support bridging for Class methods return types (#51223)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51223

Changelog:
[General][Added] - Added support for bridging Class methods return types

Previously, this wouldn't work, unless you define your C++ implementation of the TM to have primitive return type that can be converted to JavaScript's type.

Reviewed By: javache

Differential Revision: D74478572

fbshipit-source-id: 75c7f589559394704446be1ebac245d38a5c4b2b

packages/react-native/ReactCommon/react/bridging/Class.h

@@ -41,7 +41,7 @@ T callFromJs(
         rt, fromJs<Args>(rt, std::forward<JSArgs>(args), jsInvoker)...);
     return jsi::Value();
 
-  } else if constexpr (is_jsi_v<T>) {
+  } else if constexpr (is_jsi_v<T> || supportsToJs<R, T>) {
     static_assert(supportsToJs<R, T>, "Incompatible return type");
 
     return toJs(
@@ -49,7 +49,6 @@ T callFromJs(
         (instance->*method)(
             rt, fromJs<Args>(rt, std::forward<JSArgs>(args), jsInvoker)...),
         jsInvoker);
-
   } else if constexpr (is_optional_jsi_v<T>) {
     static_assert(
         is_optional_v<R>

packages/react-native/ReactCommon/react/bridging/tests/ClassTest.cpp

@@ -92,4 +92,62 @@ TEST_F(BridgingTest, callFromJsTest) {
   EXPECT_TRUE(called);
 }
 
+struct MethodReturnTypeCastingTestObject {
+ public:
+  explicit MethodReturnTypeCastingTestObject(int value) : value_(value) {}
+
+  int toInteger() const {
+    return value_;
+  }
+
+ private:
+  int value_;
+};
+
+template <>
+struct Bridging<MethodReturnTypeCastingTestObject> {
+  static MethodReturnTypeCastingTestObject fromJs(
+      jsi::Runtime& /*rt*/,
+      const jsi::Value& value) {
+    return MethodReturnTypeCastingTestObject(
+        static_cast<int>(value.asNumber()));
+  }
+
+  static int toJs(
+      jsi::Runtime& /*rt*/,
+      const MethodReturnTypeCastingTestObject& value) {
+    return value.toInteger();
+  }
+};
+
+struct MethodReturnTypeCastingTestClass {
+  explicit MethodReturnTypeCastingTestClass(
+      std::shared_ptr<CallInvoker> invoker)
+      : invoker_(std::move(invoker)) {}
+
+  // This is the key, return type is not a primitive, but an object with defined
+  // bridging template.
+  MethodReturnTypeCastingTestObject
+  add(jsi::Runtime& /*unused*/, int a, int b) {
+    return MethodReturnTypeCastingTestObject(a + b);
+  }
+
+ private:
+  std::shared_ptr<CallInvoker> invoker_;
+};
+
+TEST_F(BridgingTest, methodReturnTypeCastingTest) {
+  auto instance = MethodReturnTypeCastingTestClass(invoker);
+
+  EXPECT_EQ(
+      2,
+      bridging::callFromJs<int>(
+          rt,
+          &MethodReturnTypeCastingTestClass::add,
+          invoker,
+          &instance,
+          1,
+          1));
+}
+
 } // namespace facebook::react