class-transformer @Transform() decorators copying is implemented

Author: korniychuk

src/api-property-ref.decorator.ts

@@ -3,7 +3,14 @@ import { DECORATORS } from '@nestjs/swagger/dist/constants';
 import { ApiPropertyOptions } from '@nestjs/swagger';
 import { createApiPropertyDecorator } from '@nestjs/swagger/dist/decorators/api-property.decorator';
 
-import { defaultMetadataStorage, TypeMetadata, ExposeMetadata, ExcludeMetadata } from './@import-fix/class-transformer';
+import {
+ defaultMetadataStorage,
+ ExcludeMetadata,
+ ExposeMetadata,
+ TransformationType,
+ TransformMetadata,
+ TypeMetadata,
+} from './@import-fix/class-transformer';
 import { getMetadataStorage, ValidationMetadata } from './@import-fix/class-validator';
 import { AnyObject, isClass, Type } from './utils';
 
@@ -213,6 +220,20 @@ export class ApiPropertyRefDecorator {
  const copy: ExcludeMetadata = { ...excludeOnClass, target: this.classProto.constructor, propertyName: undefined };
  storage.addExcludeMetadata(copy);
  }
+
+ const transformMetadataCopyCb = (meta: TransformMetadata) => {
+ const copy: TransformMetadata = { ...meta, target: this.classProto.constructor, propertyName: this.propertyKey };
+ storage.addTransformMetadata(copy);
+ };
+ // Notice: CLASS_TO_CLASS transformers is not tested, but should work.
+ // I don't understand what they do and how to use them. So I don't know how to test them and don't.
+ _.values(TransformationType).forEach(transformationTypeValue =>
+ storage.findTransformMetadatas(
+ EntityConstructor,
+ this.normalizedEntityPropertyKey,
+ transformationTypeValue as TransformationType,
+ ).forEach(transformMetadataCopyCb),
+ );
  }
 
 }

src/integration.spec.ts

@@ -1,7 +1,7 @@
 import { Body, Controller, INestApplication, Module, Post } from '@nestjs/common';
 import { Test } from '@nestjs/testing';
 
-import { classToPlain, Exclude, Expose, plainToClass, Type } from 'class-transformer';
+import { classToPlain, Exclude, Expose, plainToClass, Transform, Type } from 'class-transformer';
 import { IsInt, IsString, Max, Min, validate } from 'class-validator';
 import { ApiProperty, DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
 import { ReferenceObject, SchemaObject } from '@nestjs/swagger/dist/interfaces/open-api-spec.interface';
@@ -350,6 +350,54 @@ describe('Integration tests', () => {
  expect(raw).toEqual({ name: ins.name });
  });
  }); // END @Expose() & @Exclude() together
+
+ describe(`@${ Transform.name }() decorators`, () => {
+ describe('Copying @Transform() decorators from an Entity to a DTO.', () => {
+ it('Should copy PLAIN_TO_CLASS decorators', () => {
+ // arrange
+ const date = new Date();
+ class User {
+ @Transform(({ value }) => new Date(value))
+ public createdAt!: Date;
+ }
+ @ApiEntityRef(User)
+ class UserCreateDto {
+ @ApiPropertyRef()
+ public createdAt!: Date;
+ }
+ const raw = { createdAt: date.toISOString() };
+
+ // act
+ const ins = plainToClass(UserCreateDto, raw);
+
+ // assert
+ expect(ins.createdAt).toBeInstanceOf(Date);
+ expect(ins.createdAt.toISOString()).toEqual(date.toISOString());
+ });
+
+ it('Should copy CLASS_TO_PLAIN decorators', () => {
+ // arrange
+ const date = new Date();
+ class User {
+ @Transform(({ value }) => (value as Date).toISOString(), { toPlainOnly: true })
+ public createdAt!: Date;
+ }
+ @ApiEntityRef(User)
+ class UserCreateDto {
+ @ApiPropertyRef()
+ public createdAt!: Date;
+ }
+ const ins = new UserCreateDto();
+ ins.createdAt = date;
+
+ // act
+ const raw = classToPlain(ins);
+
+ // assert
+ expect(raw).toEqual({ createdAt: date.toISOString() });
+ });
+ });
+ }); // END @${ Transform.name }() decorators
  });
  });
 });