docs: mention reflect-metadata behaviour

README.md

@@ -163,6 +163,15 @@ class Foo {
 }
 ```
 
+#### reflect-metadata
+If the global `Reflect` provides `getMetadataKeys`, `getMetadata` and `defineMetadata` methods, they will be used to attach corresponding data to the decorated targets.
+To enable, just add `reflect-metadata` to your dependencies and load it.
+```ts
+import 'reflect-metadata'
+import {constructDecorator} from '@qiwi/decorator-utils'
+// ...
+```
+
 ### Refs
 * [JS decorators by Axel Rauschmayer](https://2ality.com/2022/10/javascript-decorators.html)
 * ["aspect" syntax for JS](https://github.com/tc39/proposal-decorators)

src/main/ts/utils.ts

@@ -56,12 +56,12 @@ export function getClassChain(ctor: any): any[] {
 // Proxy is slow, so we use this wrapper
 export const Refl: Pick<typeof Reflect, 'getMetadataKeys' | 'defineMetadata' | 'getMetadata'> = ({
     getMetadataKeys(target: any) {
-      return Reflect.getMetadataKeys?.(target) || []
+      return Reflect?.getMetadataKeys?.(target) || []
     },
     defineMetadata(metadataKey: any, metadataValue: any, target: any) {
-      return Reflect.defineMetadata?.(metadataKey, metadataValue, target)
+      return Reflect?.defineMetadata?.(metadataKey, metadataValue, target)
     },
     getMetadata(metadataKey: any, target: any) {
-      return Reflect.getMetadata?.(metadataKey, target)
+      return Reflect?.getMetadata?.(metadataKey, target)
     }
   })