Class-transformer: feature: ship common transforms in subdirectory

[ceopaludetto]

Description

Due to the deprecation of the class-sanitizer package, release common transformations will improve new users experience.

Proposed solution

I've imagined something like:

import { Trim, ToLowerCase } from 'class-transformer/common'

class Person {
  @Trim()
  @ToLowerCase()
  public email!: string;
}

Thus this can be achieved with this piece of code:

import { Trim } from 'class-transformer'

export function Trim() {
  return (target: any, key: string) => {
    return Transform((value: string) => value.trim())(target, key);
  };
}

Or in a more customizable way:

export function Trim(only?: "left" | "right") {
  return (target: any, key: string) => {
    return Transform((value: string) => {
      if (only) {
        if (only === "left") {
          return value.trimLeft();
        }

        return value.trimRight();
      }

      return value.trim();
    })(target, key);
  };
}

If the solution can't be shipped, encourage new users to create your own decorators to avoid mismatch between yours dtos.

Thanks for pay attention, awesome work!

[NoNameProvided]

Yes, this is on the roadmap but we need to figure out what is the best way to ship this. In the meantime feel free to use class-sanitizer the latest version is not deprecated just new development is halted. (I will deprecate only if a security bug arise.)

[ruscon]

ping, want this too.

[ruscon]

Better solution

import { Transform, TransformOptions } from 'class-transformer';

export interface TrimOptions {
    /** @default 'both' */
    strategy?: 'start' | 'end' | 'both';
}

export function Trim(options?: TrimOptions, transformOptions?: TransformOptions): (target: any, key: string) => void {
    return Transform((value: unknown) => {
        if ('string' !== typeof value) {
            return value;
        }

        switch (options?.strategy) {
            case 'start':
                return value.trimLeft();
            case 'end':
                return value.trimRight();
            default:
                return value.trim();
        }
    }, transformOptions);
}

Test

import { plainToClass } from 'class-transformer';

describe('#Trim', () => {
    class TestModel {
        @Trim()
        withDefault: string;
        @Trim({ strategy: 'start' })
        trimStart: string;
        @Trim({ strategy: 'end' })
        trimEnd: string;
        @Trim({ strategy: 'both' })
        trimBoth: string;
    }

    it('should transform with success', async () => {
        return plainToClass(TestModel, {
            withDefault: '   withDefault   ',
            trimStart: '   trimStart   ',
            trimEnd: '   trimEnd   ',
            trimBoth: '   trimBoth   ',
        }).should.eql({
            withDefault: 'withDefault',
            trimStart: 'trimStart   ',
            trimEnd: '   trimEnd',
            trimBoth: 'trimBoth',
        });
    });
});