feat(core): add autoMap mapping configuration

[gabrielkim13]

Avoid using the @AutoMap decorator by replacing it with calls to autoMap inside the profile.

---

Motivation

First of all, great job on @automapper! I'm familiar with using the O.G. AutoMapper on C# projects and this library has been a huge help for my "mapping" needs.

Nevertheless, I do have some minor pain points with it:

1. Using the @AutoMap decorator on models / DTOs definitions is undesirable, especially when used in DDD(-Lite) projects, where entity definitions are supposed to be "pure", exempt from any mapping responsibilities.

2. Although a good approach for solving the issue above, the @automapper/classes/transforme-plugin failed on me on a NestJS project in Monorepo mode; not really sure why. If it's of interest, I'm willing to submit an issue alongside a minimal repository simulating the error.

Not only that, neither can be used with constructor assignments:

class MyClass {
    constructor(public foo: string, private bar: number) {}
}

My homebrewed solution

In the end, I ended up ditching both of the solutions described above and use a local autoMap function, which is a simple wrapper over forMember:

export function autoMap<
    TSource extends { [key in TKey]: TValue },
    TDestination extends { [key in TKey]: TValue },
    TKey extends keyof TSource & keyof TDestination,
    TValue extends TSource[TKey] & TDestination[TKey]
>(prop: TKey): MappingConfiguration<TSource, TDestination> {
    return forMember(
        (dest) => dest[prop] as TValue,
        mapFrom((src) => src[prop])
    );
}

Then it can be used as:

createMap(
    mapper,
    DecoratorlessUser,
    DecoratorlessUserDto,
    autoMap('firstName'),
    autoMap('lastName'),
    forMember(
        (d) => d.fullName,
        mapFrom((s) => s.firstName + ' ' + s.lastName)
    )
);

Not really sure if it's worthy to be included on the lib. Just thought I would share my issues with it and my approach to working around them.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
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No Coverage information
0.0% Duplication

[nartc]

Although a good approach for solving the issue above, the @automapper/classes/transforme-plugin failed on me on a NestJS project in Monorepo mode; not really sure why. If it's of interest, I'm willing to submit an issue alongside a minimal repository simulating the error.

Please do provide the reproduce. Thank you for the PR.

Also, can you please write the doc for autoMap()?

[gabrielkim13]

Thank you for reviewing and merging this PR @nartc!

I submitted a new PR adding the docs for autoMap(), as per your request: #539.

---

I tried reproducing the error from @automapper/classes/transformer-plugin in a minimal project using Nest's Monorepo mode, but everything works out as expected when using the Nest CLI. I guess I was doing something wrong the first time around 😅.

In any case, I couldn't figure out how to successfully configure the transformer plugin to run with ts-jest. Here is the minimal reproduction repo: https://github.com/gabrielkim13/automapper-transformer-plugin-nestjs-monorepo.

The transform configuration is based on their official docs: AST transformers option.

[nartc]

@gabrielkim13 Looks like ts-jest requires the plugin to have name and version (for caching purposes). I added it on main but haven't tested. I'll be releasing it soon after some testing.

[gabrielkim13]

@nartc, I got the transformer plugin working by following the instructions on https://docs.nestjs.com/openapi/cli-plugin#integration-with-ts-jest-e2e-tests.

// automapper.plugin.ts

import * as plugin from '@automapper/classes/transformer-plugin';

export const name = '@automapper/classes/transformer-plugin';
export const version = 1;

export const factory = (cs) => {
  return plugin.before({ modelFileNameSuffix: ['.dto.ts'] }, cs.program);
};

// jest.config.ts

import type { JestConfigWithTsJest } from 'ts-jest';

export default {
  // ...
  transform: {
    '^.+\\.tsx?$': [
      'ts-jest',
      {
        astTransformers: {
          before: ['<rootDir>/automapper.plugin.ts'],
        },
      },
    ],
  },
} satisfies JestConfigWithTsJest;