Hanami persistence proposal for 2.x

proposals
7

So I’ll comment on this in full soon enough, but in the meantime, I did want to point out one thing.

Over in my example app I’ve just moved my relation classes into app/, as a way to start getting a feel for the structure @jodosha has outlined above: Move relations to app/ by timriley · Pull Request #17 · decafsucks/decafsucks · GitHub

This change required I change my rom auto-registration setup to the following:

    rom_config.auto_registration(
      target.root.join("app"),
      namespace: Hanami.app.namespace.to_s
    )

With target.root.join("app") being given as the auto_registration directory, it means that rom will also look there for mappers/ and commands/ subdirectories, as well as the expected relations/.

Now defining custom mappers and commands is fairly advanced rom usage, but either way, I don’t think we’d want to see these defined in top-level directories under app. Those directories feel much too prominent for what are otherwise fairly niche concerns.

In addition, there’s a fair chance from naming collisions here too: “mappers” and “commands” are fairly common terms and there’s a non-zero chance that a user will try and create directories like those as the namespace for unrelated objects.

I tried passing this option to rom’s auto_registration method:

component_dirs: {
  relations: :relations
}

As well as this:

component_dirs: {
  relations: relations,
  mappers: nil,
  commands: nil,
}

But both of these failed because rom’s auto-registration setup expects these to be defined at all times.

I think this points to the need for rom’s auto-registration setup to be a little more flexible. Ideally I think we’d want the following:

  1. Ability to auto-register relations only in with one given root dir (app/) and namespace (e.g. "AppNamespace::Relations")
  2. And then to separately auto-register mappers and commands with different given root dir and namespace

Implicit in the above is that any for any single rom auto_registration call, it should be possible to disable registration for particular component types, such as mappers and commends.

Then after this, as a separate matter, we’d want to think about how whether we want to support default auto-registration for rom mappers and commands within Hanami apps, and if so, what directories they should use.

I suppose an alternative for Hanami’s rom setup could be to avoid rom’s auto_register entirely, and instead find and manually register all the rom components. But it’d probably be nice if we could make rom’s auto_register more flexible anyway :slight_smile:

cc @solnic since I think these could be useful things to solve with the upcoming version of rom.