fix: lookup up property descriptors on the prototype (#1258)

Author: CodyTseng

src/TransformOperationExecutor.ts

@@ -295,7 +295,7 @@ export class TransformOperationExecutor {
 
         // if newValue is a source object that has method that match newKeyName then skip it
         if (newValue.constructor.prototype) {
-          const descriptor = Object.getOwnPropertyDescriptor(newValue.constructor.prototype, newValueKey);
+          const descriptor = this.getPropertyDescriptor(newValue.constructor.prototype, newValueKey);
           if (
             (this.transformationType === TransformationType.PLAIN_TO_CLASS ||
               this.transformationType === TransformationType.CLASS_TO_CLASS) &&
@@ -544,4 +544,12 @@ export class TransformOperationExecutor {
 
     return this.options.groups.some(optionGroup => groups.includes(optionGroup));
   }
+
+  private getPropertyDescriptor(obj: any, key: PropertyKey): PropertyDescriptor | undefined {
+    const descriptor = Object.getOwnPropertyDescriptor(obj, key);
+    if (descriptor) return descriptor;
+
+    const prototype = Object.getPrototypeOf(obj);
+    return prototype ? this.getPropertyDescriptor(prototype, key) : undefined;
+  }
 }

test/functional/basic-functionality.spec.ts

@@ -1664,6 +1664,55 @@ describe('basic functionality', () => {
     expect(transformedUser).toEqual(likeUser);
   });
 
+  it('should expose inherited method and accessors that have @Expose()', () => {
+    class User {
+      firstName: string;
+      lastName: string;
+
+      @Expose()
+      get name() {
+        return this.firstName + ' ' + this.lastName;
+      }
+
+      @Expose()
+      getName() {
+        return this.firstName + ' ' + this.lastName;
+      }
+    }
+    class Programmer extends User {
+      language: string;
+    }
+
+    const programmer = new Programmer();
+    programmer.firstName = 'Umed';
+    programmer.lastName = 'Khudoiberdiev';
+    programmer.language = 'en';
+
+    const fromPlainProgrammer = {
+      firstName: 'Umed',
+      lastName: 'Khudoiberdiev',
+      language: 'en',
+    };
+
+    const plainProgrammer: any = instanceToPlain(programmer);
+    expect(plainProgrammer).not.toBeInstanceOf(Programmer);
+    expect(plainProgrammer).toEqual({
+      firstName: 'Umed',
+      lastName: 'Khudoiberdiev',
+      language: 'en',
+      name: 'Umed Khudoiberdiev',
+      getName: 'Umed Khudoiberdiev',
+    });
+
+    const transformedProgrammer = plainToInstance(Programmer, fromPlainProgrammer);
+    expect(transformedProgrammer).toBeInstanceOf(Programmer);
+    const likeProgrammer = new Programmer();
+    likeProgrammer.firstName = 'Umed';
+    likeProgrammer.lastName = 'Khudoiberdiev';
+    likeProgrammer.language = 'en';
+    expect(transformedProgrammer).toEqual(likeProgrammer);
+  });
+
   it('should transform array', () => {
     defaultMetadataStorage.clear();