External mapping definition

[tehmaestro]

Hi, super useful library, it was exactly what I needed and it works great for our project, really appreciate your work.
One question I have, would you be open to having the mappings defined as external files, like yaml?

The attributes added in the Application layer DTOs currently break our Clean Architecture setup.

[Pixelshaped]

Hi thanks!

I think FlatMapper DTOs are intended to live in Infrastructure (adapter/read-model layer), not in the Application core.
In an anemic domain style, this can work fine without extra mapping if both classes implement the same domain contract:

src/
├── Domain/Billing/BillableInterface.php
├── Domain/Billing/BillService.php
├── Domain/Author/Author.php                         # implements BillableInterface
├── Application/Billing/GenerateBillsHandler.php
└── Infrastructure/Author/ReadModel/AuthorDto.php.   # FlatMapper DTO, also implements BillableInterface

In that setup, FlatMapper DTOs are typically read-optimized subsets of entity data, tailored to specific views/use cases.
In a rich domain model, this is usually not enough because invariants/behavior live in aggregates.

For me the benefits of adding YAML/external mapping would be:

• Map classes you can’t modify (vendor/shared classes).
• Maintain multiple mapping profiles per use case without duplicating classes.

If the goal is to hydrate the same class across strict inner layers, that can reintroduce ORM-style persistence coupling (similar to using Doctrine entities as DDD entities).

That being said, I'm open to supporting YAML mappings as an optional mode. I can look into it :)

[Pixelshaped]

It was a rainy weekend. Can I let you review @tehmaestro if that suits your needs?

[tehmaestro]

Hey, super cool, I actually wanted to create a PR, that's why I asked if you're open to it, but it seems you've done it already. Thanks, will try it tomorrow.
For anybody wondering, my setup is like this:

Application
  - SomeService.php
  - MapperInterface.php
Domain
  - RepositoryInterface.php
Infrastructure
  - Repository.php
  - FlatMapper.php

SomeService uses the RepositoryInterface to execute a custom query made with DQL and then uses the MapperInterface to map the resulted array. To me it made sense to have the the infrastructure layer execute the mapping and return Application layer DTOs. Having an external mapping means the Application layer DTOs remain decoupled from the actual implementation in the infrastructure (meaning the FlatMapper attributes).

[Pixelshaped]

@tehmaestro let me know if everything worked out for you!

[tehmaestro]

Yes, works great for me
Thank you.