feat: implement extend decorator

src/extend.ts

@@ -0,0 +1,23 @@
+import 'reflect-metadata';
+import { extendRecursively } from './utils';
+
+export function Extend(): ClassDecorator {
+	return (constructor: Function): void => {
+		const instance: Object = constructor.prototype;
+		const instanceProto: Object = Object.getPrototypeOf(instance);
+
+		for (const propertyKey of Object.getOwnPropertyNames(instance)) {
+			const metadataKeys =
+				propertyKey === 'constructor'
+					? Reflect.getOwnMetadataKeys(instance.constructor)
+					: Reflect.getOwnMetadataKeys(instance, propertyKey);
+
+			extendRecursively(
+				instance,
+				metadataKeys,
+				propertyKey,
+				instanceProto,
+			);
+		}
+	};
+}

src/utils.ts

@@ -0,0 +1,81 @@
+export function extendRecursively(
+	instance: Object,
+	metadataKeys: any[], // eslint-disable-line
+	propertyKey: string | symbol,
+	instanceProto: Object,
+): void {
+	if (propertyKey === 'constructor')
+		extendConstructorRec(instance, metadataKeys, instanceProto);
+	else extendPropertyRec(instance, metadataKeys, propertyKey, instanceProto);
+}
+
+function extendConstructorRec(
+	instance: Object,
+	metadataKeys: any[], // eslint-disable-line
+	instanceProto: Object,
+) {
+	if (!instanceProto || !instanceProto.constructor) return;
+
+	const protoMetadataKeys = Reflect.getOwnMetadataKeys(
+		instanceProto.constructor,
+	);
+	for (const metadataKey of protoMetadataKeys) {
+		if (metadataKeys.includes(metadataKey)) continue;
+
+		const metadataValue = Reflect.getOwnMetadata(
+			metadataKey,
+			instanceProto.constructor,
+		);
+
+		Reflect.defineMetadata(
+			metadataKey,
+			metadataValue,
+			instance.constructor,
+		);
+		metadataKeys.push(metadataKey);
+	}
+
+	extendConstructorRec(
+		instance,
+		metadataKeys,
+		Object.getPrototypeOf(instanceProto),
+	);
+}
+
+function extendPropertyRec(
+	instance: Object,
+	metadataKeys: any[], // eslint-disable-line
+	propertyKey: string | symbol,
+	instanceProto: Object,
+) {
+	if (!instanceProto || !instanceProto.hasOwnProperty(propertyKey)) return;
+
+	const protoMetadataKeys = Reflect.getOwnMetadataKeys(
+		instanceProto,
+		propertyKey,
+	);
+	for (const metadataKey of protoMetadataKeys) {
+		if (metadataKeys.includes(metadataKey)) continue;
+
+		const metadataValue = Reflect.getOwnMetadata(
+			metadataKey,
+			instanceProto,
+			propertyKey,
+		);
+
+		Reflect.defineMetadata(
+			metadataKey,
+			metadataValue,
+			instance,
+			propertyKey,
+		);
+		metadataKeys.push(metadataKey);
+	}
+
+	extendPropertyRec(
+		instance,
+		metadataKeys,
+		propertyKey,
+		Object.getPrototypeOf(instanceProto),
+	);
+}