PoC: Isolate dependency injections by specific pattern

[davydovanton]

Hey, I have a idea how to improve injector for scopes in business logic.

I create simple PR for discussing and share this idea

Idea

Imagine a situation when you have an application with 2 different scopes: Accounts and Orders. And in each scope (or domain) you have specific operations and repositories. And in account repo we have a similar method name find:

module Accounts
  # Operations for accounts
  module Operations
    class List
      # ...
    end

    class Show
      # ...
    end
  end

  # Repos for accounts
  module Repositories
    class Accounts
      def find(id)
        # ...
      end
    end
  end
end

module Orders
  # Operation for orders
  module Operations
    class Create
      # ...
    end

    class Checkout
      # ...
    end
  end

  # Repos for orders
  module Repositories
    class Orders
      # ...
    end

    class Accounts
      def find(order_id)
        # ...
      end
    end
  end
end

We put all these classes into a container and now we can fail if someone injects account repo from Accounts to Orders scope:

module Orders
  # Operation for orders
  module Operations
    class Create
      # OK for us
      include Inject['orders.repositories.accounts']

      # BAD but we get a exeption ONLY after first call
      include Inject['accounts.repositories.accounts']

      # ...
    end
  end
end

---

Important thing

This code (with injection 'accounts.repositories.accounts') raise error only after booting and first real call.

---

For detecting these situations I introduce allow method with simple regexp pattern:

module Accounts
  Inject = Inject.allow(/\Aaccounts.+/) # allow to inject only "accounts.*" keys

  # ...
end

module Orders
  Inject = Inject.allow(/\Aorders.+/) # allow to inject only "orders.*" keys

  module Operations
    class Create
      include Inject['orders.repositories.accounts'] # OK for us
      include Inject['accounts.repositories.accounts'] # raise error on object initialization step

      # ...
    end
  end

  # ...
end

And now, if we will try to inject 'accounts.repositories.accounts' to Orders::Operations::Create we fail on creating an instance of operation.

Implementation

It's just a proposal of my vision. I'm not sure that allow better name for this. But I'll be happy to discuss it with everyone ❤️

[davydovanton]

cc @solnic @timriley @flash-gordon @GustavoCaso

[rbUUbr]

I think, it will be better to raise some fixed error, not RuntimeError. I think, it would be great for programmers. WDYT about it?

[solnic]

Here is an overview of what got changed by this pull request:

Issues
======
- Added 4
           

See the complete overview on Codacy

[solnic]

Issue found: Redundant curly braces around a hash parameter.

[solnic]

Issue found: Prefer single-quoted strings when you don't need string interpolation or special symbols.

[solnic]

Issue found: Prefer single-quoted strings when you don't need string interpolation or special symbols.

[solnic]

Issue found: Space inside } missing.