[V8] Implement object properties accessor

Author: tonyfreeman

Sources/CV8/include/wrappers.h

@@ -35,7 +35,7 @@ extern "C" {
     // called from JSValue's destructor
     void disposeValue(void * _Nonnull pointer);
 
-    void * _Nullable evaluate(void * _Nonnull isolatePtr, void * _Nonnull contextPtr, const char* _Nonnull scriptPtr, void * _Nullable* _Nonnull exception);
+    void * _Nullable evaluate(void * _Nonnull isolatePtr, void * _Nonnull contextPtr, const char* _Nonnull scriptPtr, void * _Nullable* _Nullable exception);
 
     int getUtf8StringLength(void * _Nonnull isolatePtr, void * _Nonnull valuePtr);
     void copyUtf8String(void * _Nonnull isolatePtr, void * _Nonnull valuePtr, void * _Nonnull buffer, int count);
@@ -61,6 +61,8 @@ extern "C" {
     void setReturnValueString(void * _Nonnull isolatePtr, void * _Nonnull returnValuePtr, const char* _Nonnull utf8);
     void setReturnValueEmptyString(void * _Nonnull isolatePtr, void * _Nonnull returnValuePtr);
 
+    void * _Nullable getProperty(void * _Nonnull isolate, void * _Nonnull value, const char * _Nonnull key, void * _Nullable* _Nullable exception);
+
 
 #ifdef __cplusplus
 }

Sources/CV8/wrappers.cpp

@@ -132,7 +132,9 @@ extern "C" {
         MaybeLocal<Value> result = script->Run(context);
 
         if (result.IsEmpty()) {
-            *exception = new Global<Value>(isolate, trycatch.Exception());
+            if (exception != nullptr) {
+                *exception = new Global<Value>(isolate, trycatch.Exception());
+            }
             return nullptr;
         }
         auto local = result.ToLocalChecked();
@@ -264,4 +266,28 @@ extern "C" {
         auto returnValue = reinterpret_cast<ReturnValue<Value>*>(returnValuePtr);
         returnValue->SetEmptyString();
     }
+
+    // MARK: properties
+
+    void* getProperty(void* isolatePtr, void* valuePtr, const char* keyPtr, void** exception) {
+        auto isolate = reinterpret_cast<Isolate*>(isolatePtr);
+        auto value = reinterpret_cast<Global<Value>*>(valuePtr);
+
+        Locker isolateLocker(isolate);
+        TryCatch trycatch(isolate);
+        Isolate::Scope isolate_scope(isolate);
+        HandleScope handle_scope(isolate);
+
+        auto object = value->Get(isolate)->ToObject();
+        auto key = String::NewFromUtf8(isolate, keyPtr);
+        auto result = object->GetRealNamedProperty(key);
+
+        if (result.IsEmpty()) {
+            if (exception != nullptr) {
+                *exception = new Global<Value>(isolate, trycatch.Exception());
+            }
+            return nullptr;
+        }
+        return new Global<Value>(isolate, result);
+    }
 }

Sources/V8/JSValue.swift

@@ -63,6 +63,18 @@ extension JSValue: JavaScript.JSValue {
     }
 }
 
+extension JSValue {
+    subscript(_ key: String) -> JSValue? {
+        guard isObject else {
+            return nil
+        }
+        guard let result = getProperty(isolate, pointer, key, nil) else {
+            return nil
+        }
+        return JSValue(isolate: isolate, pointer: result)
+    }
+}
+
 extension JSValue: CustomStringConvertible {
     public var description: String {
         return try! toString()

Tests/V8Tests/JSValueTests.swift

@@ -109,4 +109,20 @@ final class JSValueTests: TestCase {
             fail(String(describing: error))
         }
     }
+
+    func testProperty() {
+        do {
+            let runtime = JSRuntime()
+            let context = JSContext(runtime)
+            let result = try context.evaluate("""
+                (function(){
+                    return { property: 'test' }
+                })()
+                """)
+
+            assertEqual(try result["property"]?.toString(), "test")
+        } catch {
+            fail(String(describing: error))
+        }
+    }
 }

Tests/V8Tests/XCTestManifests.swift

@@ -7,6 +7,7 @@ extension JSValueTests {
         ("testIsNumber", testIsNumber),
         ("testIsString", testIsString),
         ("testIsUndefined", testIsUndefined),
+        ("testProperty", testProperty),
         ("testToInt", testToInt),
         ("testToString", testToString),
     ]