Support optional return types

Summary:
This fixes an issue in the C++ TurboModule codegen where optional return types would result in a compiler error because they were not being defaulted to `null` when converting to `jsi::Value`.

Changelog:
Internal

Reviewed By: javache

Differential Revision: D36989312

fbshipit-source-id: 525f9ce7a5638ba5a655fa69ba9647978030ab0b

ReactCommon/react/bridging/Class.h

@@ -50,6 +50,27 @@ T callFromJs(
             rt, fromJs<Args>(rt, std::forward<JSArgs>(args), jsInvoker)...),
         jsInvoker);
 
+  } else if constexpr (is_optional_v<T>) {
+    static_assert(
+        is_optional_v<R>
+            ? supportsToJs<typename R::value_type, typename T::value_type>
+            : supportsToJs<R, typename T::value_type>,
+        "Incompatible return type");
+
+    auto result = toJs(
+        rt,
+        (instance->*method)(
+            rt, fromJs<Args>(rt, std::forward<JSArgs>(args), jsInvoker)...),
+        jsInvoker);
+
+    if constexpr (std::is_same_v<decltype(result), jsi::Value>) {
+      if (result.isNull() || result.isUndefined()) {
+        return std::nullopt;
+      }
+    }
+
+    return convert(rt, std::move(result));
+
   } else {
     static_assert(std::is_convertible_v<R, T>, "Incompatible return type");
 

ReactCommon/react/bridging/Convert.h

@@ -24,6 +24,15 @@ inline constexpr bool is_jsi_v =
     std::is_same_v<jsi::String, remove_cvref_t<T>> ||
     std::is_base_of_v<jsi::Object, remove_cvref_t<T>>;
 
+template <typename>
+struct is_optional : std::false_type {};
+
+template <typename T>
+struct is_optional<std::optional<T>> : std::true_type {};
+
+template <typename T>
+inline constexpr bool is_optional_v = is_optional<T>::value;
+
 template <typename T>
 struct Converter;
 

packages/react-native-codegen/src/generators/modules/GenerateModuleCpp.js

@@ -17,6 +17,7 @@ import type {
   NativeModulePropertyShape,
   NativeModuleFunctionTypeAnnotation,
   NativeModuleParamTypeAnnotation,
+  NativeModuleTypeAnnotation,
 } from '../../CodegenSchema';
 
 import type {AliasResolver} from './Utils';
@@ -28,21 +29,33 @@ type FilesOutput = Map<string, string>;
 const HostFunctionTemplate = ({
   hasteModuleName,
   methodName,
-  isVoid,
+  returnTypeAnnotation,
   args,
 }: $ReadOnly<{
   hasteModuleName: string,
   methodName: string,
-  isVoid: boolean,
+  returnTypeAnnotation: Nullable<NativeModuleTypeAnnotation>,
   args: Array<string>,
 }>) => {
+  const isNullable = returnTypeAnnotation.type === 'NullableTypeAnnotation';
+  const isVoid = returnTypeAnnotation.type === 'VoidTypeAnnotation';
   const methodCallArgs = ['rt', ...args].join(', ');
-  const methodCall = `static_cast<${hasteModuleName}CxxSpecJSI *>(&turboModule)->${methodName}(${methodCallArgs});`;
+  const methodCall = `static_cast<${hasteModuleName}CxxSpecJSI *>(&turboModule)->${methodName}(${methodCallArgs})`;
 
   return `static jsi::Value __hostFunction_${hasteModuleName}CxxSpecJSI_${methodName}(jsi::Runtime &rt, TurboModule &turboModule, const jsi::Value* args, size_t count) {${
-    isVoid ? `\n  ${methodCall}` : ''
+    isVoid
+      ? `\n  ${methodCall};`
+      : isNullable
+      ? `\n  auto result = ${methodCall};`
+      : ''
   }
-  return ${isVoid ? 'jsi::Value::undefined();' : methodCall}
+  return ${
+    isVoid
+      ? 'jsi::Value::undefined()'
+      : isNullable
+      ? 'result ? jsi::Value(std::move(*result)) : jsi::Value::null()'
+      : methodCall
+  };
 }`;
 };
 
@@ -173,13 +186,11 @@ function serializePropertyIntoHostFunction(
 ): string {
   const [propertyTypeAnnotation] =
     unwrapNullable<NativeModuleFunctionTypeAnnotation>(property.typeAnnotation);
-  const isVoid =
-    propertyTypeAnnotation.returnTypeAnnotation.type === 'VoidTypeAnnotation';
 
   return HostFunctionTemplate({
     hasteModuleName,
     methodName: property.name,
-    isVoid,
+    returnTypeAnnotation: propertyTypeAnnotation.returnTypeAnnotation,
     args: propertyTypeAnnotation.params.map((p, i) =>
       serializeArg(p, i, resolveAlias),
     ),

packages/react-native-codegen/src/generators/modules/__tests__/__snapshots__/GenerateModuleCpp-test.js.snap

@@ -62,13 +62,16 @@ static jsi::Value __hostFunction_NativeSampleTurboModuleCxxSpecJSI_getArrays(jsi
   return jsi::Value::undefined();
 }
 static jsi::Value __hostFunction_NativeSampleTurboModuleCxxSpecJSI_getNullableObject(jsi::Runtime &rt, TurboModule &turboModule, const jsi::Value* args, size_t count) {
-  return static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableObject(rt);
+  auto result = static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableObject(rt);
+  return result ? jsi::Value(std::move(*result)) : jsi::Value::null();
 }
 static jsi::Value __hostFunction_NativeSampleTurboModuleCxxSpecJSI_getNullableGenericObject(jsi::Runtime &rt, TurboModule &turboModule, const jsi::Value* args, size_t count) {
-  return static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableGenericObject(rt);
+  auto result = static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableGenericObject(rt);
+  return result ? jsi::Value(std::move(*result)) : jsi::Value::null();
 }
 static jsi::Value __hostFunction_NativeSampleTurboModuleCxxSpecJSI_getNullableArray(jsi::Runtime &rt, TurboModule &turboModule, const jsi::Value* args, size_t count) {
-  return static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableArray(rt);
+  auto result = static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableArray(rt);
+  return result ? jsi::Value(std::move(*result)) : jsi::Value::null();
 }
 
 NativeSampleTurboModuleCxxSpecJSI::NativeSampleTurboModuleCxxSpecJSI(std::shared_ptr<CallInvoker> jsInvoker)
@@ -109,7 +112,8 @@ static jsi::Value __hostFunction_NativeSampleTurboModuleCxxSpecJSI_getMixed(jsi:
   return static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getMixed(rt, jsi::Value(rt, args[0]));
 }
 static jsi::Value __hostFunction_NativeSampleTurboModuleCxxSpecJSI_getNullableNumberFromNullableAlias(jsi::Runtime &rt, TurboModule &turboModule, const jsi::Value* args, size_t count) {
-  return static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableNumberFromNullableAlias(rt, args[0].isNull() || args[0].isUndefined() ? std::nullopt : std::make_optional(args[0].asObject(rt)));
+  auto result = static_cast<NativeSampleTurboModuleCxxSpecJSI *>(&turboModule)->getNullableNumberFromNullableAlias(rt, args[0].isNull() || args[0].isUndefined() ? std::nullopt : std::make_optional(args[0].asObject(rt)));
+  return result ? jsi::Value(std::move(*result)) : jsi::Value::null();
 }
 
 NativeSampleTurboModuleCxxSpecJSI::NativeSampleTurboModuleCxxSpecJSI(std::shared_ptr<CallInvoker> jsInvoker)