inject-dependencies

name	inject-dependencies
license	MIT
type	atomic
description	Use when injecting dependencies in Hanami 2.x — always use `include Deps["dir.name"]` to inject (never call `Hanami.app["key"]` directly outside of providers), derive container keys from file paths via `app/{dir}/{name}.rb` → `"{dir}.{name}"`, exclude ROM-managed relations/structs/entities from auto-registration via `no_auto_register_paths`, access the dependency by its last key segment — for example `Deps["repos.user_repo"]` → use `user_repo`, and override dependencies in tests by passing stubs to `.new(keyword:)`. Covers container keys, auto-registration rules, no_auto_register_paths, and testing with stubs.
metadata	{"ecosystem_sources":["dry-rb/dry-system","hanami/hanami"],"tags":["di","dependencies","container","deps"],"version":"1.0.0"}

inject-dependencies

Use this skill when injecting dependencies into Hanami 2.x components.

Core principle: Dependencies are injected, not looked up. Never access the container directly — always use include Deps[].

---

Quick Reference

Scenario	Approach
Inject a dependency	include Deps["repos.user_repo"]
Inject multiple dependencies	include Deps["repos.user_repo", "views.users.index"]
Access injected dependency	Call the method name matching the last segment of the key: user_repo
Auto-registered key	File app/repos/user_repo.rb → key "repos.user_repo"
Exclude from auto-registration	Add path to no_auto_register_paths in the slice config
Test with stubs	Pass stubbed dependencies when instantiating the component
Override dependency	Pass the dependency as a keyword argument to .new

---

Core Rules

1. Always use include Deps[] to inject dependencies:

   # app/actions/users/index.rb
   # frozen_string_literal: true
   
   module MyApp
     module Actions
       module Users
         class Index < MyApp::Action
            include Deps["repos.user_repo"]
   
            def handle(request, response)
              # `view` is resolved by Hanami from the Action class name convention
              response.render(view, users: user_repo.all)
            end
         end
       end
     end
   end
   

2. The container key is derived from the file path:

   app/repos/user_repo.rb     → "repos.user_repo"
   app/views/users/index.rb   → "views.users.index"
   app/relations/users.rb     → "relations.users"
   

   Rule: app/{dir}/{name}.rb maps to container key "{dir}.{name}".

3. Certain directories are excluded from auto-registration because ROM manages them directly:

   • relations/
   • structs/
   • entities/

   These are handled by ROM and should not be auto-registered by dry-system.

4. Add custom exclusions in the slice configuration:

   # config/app.rb
   # frozen_string_literal: true
   
   module MyApp
     class App < Hanami::App
       config.no_auto_register_paths = ["app/serializers"]
     end
   end
   

5. Override dependencies in tests by passing them to .new:

   stub_repo = double("user_repo", all: [])
   action = MyApp::Actions::Users::Index.new(user_repo: stub_repo)
   

6. Never access the container directly:

   # BAD
   repo = Hanami.app["repos.user_repo"]
   
   # GOOD
   include Deps["repos.user_repo"]
   # use user_repo directly
   

---

Anti-Patterns & Mistakes

Mistake	Correct Approach
Hanami.app['key'] inside an Action	Direct container access is untestable. Always use include Deps[].
Guessing container keys	Keys follow app/{dir}/{name}.rb → "{dir}.{name}". Learn the rule, do not guess.
Auto-registering relations/, structs/, or entities/	These are managed by ROM. Adding them to auto-registration causes boot errors.
Custom initialize for dependency injection	Deps mixin handles constructor injection for you. Do not write custom initialize methods for DI.
Forgetting to update tests after renaming a file	When you move a file, the container key changes. Update all Deps[] references and test stubs.
Accessing the full key name as a method	Access by the last segment only: include Deps["repos.user_repo"] → use user_repo.