Fix metadata map getting recreated

package.json

@@ -10,6 +10,7 @@
     "clean": "rimraf dist",
     "prebuild": "npm run clean",
     "prepare": "npm run build",
+    "start": "jest --watch",
     "test": "jest"
   },
   "repository": {

src/define-metadata.test.ts

@@ -1,22 +1,27 @@
 import { Reflection as Reflect } from './index';
 
+const metadataKey = 'key';
+const metadataValue = 'value';
+const target = {};
+
 test('with invalid target', () => {
-  const metadataKey = 'key';
-  const metadataValue = 'value';
   expect(() => Reflect.defineMetadata(metadataKey, metadataValue)).toThrow(TypeError);
 });
 
 test('with target but no property key', () => {
-  const metadataKey = 'key';
-  const metadataValue = 'value';
-  const target = {};
   expect(() => Reflect.defineMetadata(metadataKey, metadataValue, target)).not.toThrow();
 });
 
 test('with target and property key', () => {
-  const metadataKey = 'key';
-  const metadataValue = 'value';
-  const target = {};
   const propertyKey = 'name';
   expect(() => Reflect.defineMetadata(metadataKey, metadataValue, target, propertyKey)).not.toThrow();
 });
+
+test('metadata map is reused', () => {
+  const metadataKey2 = 'key2';
+  const metadataValue2 = 'value2';
+  Reflect.defineMetadata(metadataKey, metadataValue, target);
+  Reflect.defineMetadata(metadataKey2, metadataValue2, target);
+  expect(Reflect.getOwnMetadata(metadataKey, target)).toEqual(metadataValue);
+  expect(Reflect.getOwnMetadata(metadataKey2, target)).toEqual(metadataValue2);
+});

src/index.ts

@@ -71,7 +71,7 @@ function decorateProperty(decorators: MemberDecorator[], target: Target, propert
 function ordinaryDefineOwnMetadata(metadataKey: MetadataKey, metadataValue: MetadataValue, target: Target, propertyKey?: PropertyKey): void {
   if (propertyKey && !['string', 'symbol'].includes(typeof propertyKey)) throw new TypeError();
 
-  createMetadataMap(target, propertyKey)
+  (getMetadataMap(target, propertyKey) || createMetadataMap(target, propertyKey))
     .set(metadataKey, metadataValue);
 }