Validation issues using special mapped-types

dto.spec.ts

import {
  IntersectionType,
  OmitType,
  PartialType,
  PickType,
} from '@nestjs/mapped-types';
import { IsNotEmpty, IsString, Length, validate } from 'class-validator';

export class Base {
  @IsString()
  @Length(2, 100)
  subject?: string;
}

export class Create extends Base {
  @IsNotEmpty()
  subject: string;
}

describe('Create', () => {
  let create: Create;

  beforeEach(() => {
    create = new Create();
  });

  // PASS
  describe('Validations from Create', () => {
    it('should pass if subject is filled', async () => {
      create.subject = 'asdf';
      const results = await validate(create);

      expect(results.length).toBe(0);
    });
    it('should fail if subject is not filled', async () => {
      const results = await validate(create);
      expect(results.length).toBe(1);
    });
  });

  // FAILS. Not detecting Base Validations.
  describe('Validations from Base', () => {
    it('it should fail when subject len is less than 2', async () => {
      create.subject = 'a';
      const results = await validate(create);
      expect(results.length).toBe(1);
    });

    it('it should fail when subject is not a string', async () => {
      create.subject = 1 as unknown as string;
      const results = await validate(create);
      expect(results.length).toBe(1);
    });
  });
});

export class UpdatePartialType extends PartialType(Create) {}

describe('UpdatePartialType', () => {
  let update: UpdatePartialType;

  beforeEach(() => {
    update = new UpdatePartialType();
  });

  // PASS
  describe('Validations from Create', () => {
    it('should pass if subject is complete', async () => {
      update.subject = 'asdf';
      const results = await validate(update);
      expect(results.length).toBe(0); // FAIL. Not detecting Length.
    });

    it('it should pass if subject is empty', async () => {
      const results = await validate(update);
      expect(results.length).toBe(0);
    });
  });

  // FAILS. Not detecting Base Validations.
  describe('Validations from Base', () => {
    it('it should fail when subject len is less than 2', async () => {
      update.subject = 'a';
      const results = await validate(update);
      expect(results.length).toBe(1);
    });

    it('it should fail when subject is not a string', async () => {
      update.subject = 1 as unknown as string;
      const results = await validate(update);
      expect(results.length).toBe(1);
    });
  });
});

export class UpdatePartialWithPickType extends IntersectionType(
  PartialType(Create),
  PickType(Create, ['subject']),
) {}

describe('UpdatePartialWithPickType', () => {
  let update: UpdatePartialWithPickType;

  beforeEach(() => {
    update = new UpdatePartialWithPickType();
  });

  describe('Validations from Create', () => {
    // PASS
    it('should pass if subject is filled', async () => {
      update.subject = 'asdf';
      const results = await validate(update);
      expect(results.length).toBe(0); // FAIL. Not detecting Length.
    });

    // FAILS. Not detecting IsNotEmpty when PickType is used.
    it('it should fail if subject is empty', async () => {
      const results = await validate(update);
      expect(results.length).toBe(1);
    });
  });

  // FAILS. Not detecting Base Validations.
  describe('Validations from Base', () => {
    it('it should fail when subject len is less than 2', async () => {
      update.subject = 'a';
      const results = await validate(update);
      expect(results.length).toBe(1);
    });

    it('it should fail when subject is not a string', async () => {
      update.subject = 1 as unknown as string;
      const results = await validate(update);
      expect(results.length).toBe(1);
    });
  });
});

export class UpdatePartialWithOmitType extends IntersectionType(
  OmitType(PartialType(Create), ['subject']),
  PickType(Create, ['subject']),
) {}

describe('UpdatePartial3', () => {
  let update: UpdatePartialWithOmitType;

  beforeEach(() => {
    update = new UpdatePartialWithOmitType();
  });

  // PASS
  describe('Validations from Create', () => {
    it('should pass if subject is filled', async () => {
      update.subject = 'asdf';
      const results = await validate(update);

      expect(results.length).toBe(0);
    });

    // PASS. Better than UpdatePartialWithPickType.
    it('it should fail if subject is empty', async () => {
      const results = await validate(update);
      expect(results.length).toBe(1);
    });
  });

  // FAILS. Not detecting Base Validations.
  describe('Validations from Base', () => {
    it('it should fail when subject len is less than 2', async () => {
      update.subject = 'a';
      const results = await validate(update);
      expect(results.length).toBe(1);
    });

    it('it should fail when subject is not a string', async () => {
      update.subject = 1 as unknown as string;
      const results = await validate(update);
      expect(results.length).toBe(1);
    });
  });
});