feat: implement virtual decorator

Author: LotfiMEZIANI

lib/decorators/index.ts

@@ -1,2 +1,3 @@
 export * from './prop.decorator';
 export * from './schema.decorator';
+export * from './virtual.decorator';

lib/decorators/virtual.decorator.ts

@@ -0,0 +1,29 @@
+import { VirtualTypeOptions } from 'mongoose';
+import { TypeMetadataStorage } from '../storages/type-metadata.storage';
+
+/**
+ * Interface defining property options that can be passed to `@Virtual()` decorator.
+ */
+export interface VirtualOptions {
+  options?: VirtualTypeOptions;
+  subPath?: string;
+  get?: (...args: any[]) => any;
+  set?: (...args: any[]) => any;
+}
+
+/**
+ * @Virtual decorator is used to mark a specific class property as a Mongoose virtual.
+ */
+export function Virtual(options?: VirtualOptions): PropertyDecorator {
+  return (target: object, propertyKey: string | symbol) => {
+    TypeMetadataStorage.addVirtualMetadata({
+      target: target.constructor,
+      options: options?.options,
+      name:
+        propertyKey.toString() +
+        (options?.subPath ? `.${options.subPath}` : ''),
+      setter: options?.set,
+      getter: options?.get,
+    });
+  };
+}