create-new-slice

name	create-new-slice
license	MIT
type	persona
description	Use when creating a new Slice in Hanami 2.x — including when a user wants to add a slice, scaffold a slice, create a new Hanami module, or set up a bounded context. Chains create-slice, define-routes, configure-slice, inject-dependencies, and write-request-spec to generate the slice, configure routes, set up dependencies, and write smoke tests.
metadata	{"ecosystem_sources":["hanami/hanami","dry-rb/dry-system"],"tags":["personas","slices","modularization","bounded-contexts"],"version":"1.0.0"}

create-new-slice

Use this workflow when creating a new Slice in Hanami 2.x.

---

Workflow

1. Generate Slice — Load skill: create-slice

Run the generator and register the slice:

bundle exec hanami generate slice blog

# config/app.rb
slice :blog, at: "/blog"

Verify the slice boots: bundle exec hanami console — confirm Hanami.app[:slices] includes the new slice.

---

2. Configure Routes — Load skill: define-routes

Define RESTful routes in the slice:

# slices/blog/config/routes.rb
routes.namespace "/blog" do
  resources :posts
end

Verify routes are registered: bundle exec hanami routes — confirm expected paths appear under the slice namespace.

---

3. Configure Slice — Load skill: configure-slice

Define slice-specific settings, providers, and auto-registration:

# slices/blog/config/slice.rb
module Blog
  class Slice < Hanami::Slice
    # Slice-specific settings
    setting :posts_per_page, default: 10

    # Slice-specific provider
    register_provider :cache do
      start { register(:cache, MyCache.new) }
    end
  end
end

Verify providers load without errors: bundle exec hanami console — call Blog::Slice[:cache] (or relevant key) to confirm resolution.

---

4. Setup DI — Load skill: inject-dependencies

Import required components from other slices and export what this slice provides:

# slices/blog/config/slice.rb
module Blog
  class Slice < Hanami::Slice
    # Import a component from the main app
    import keys: ["persistence.db"], from: :app

    # Export components for other slices
    export keys: ["repositories.posts"]
  end
end

Verify cross-slice dependencies resolve:

# In hanami console
Blog::Slice["persistence.db"]        # => must not raise
Hanami.app["blog.repositories.posts"] # => must not raise

---

5. Write Tests — Load skill: write-request-spec

Write smoke tests confirming the slice mounts and routes respond:

# spec/requests/blog/posts_spec.rb
RSpec.describe "Blog::Posts", type: :request do
  it "lists posts" do
    get "/blog/posts"
    expect(last_response.status).to eq(200)
  end
end

Run the smoke tests: bundle exec rspec spec/requests/blog/ — all examples must pass before considering the slice complete.

---

Pitfalls

Mistake	Correct Approach
Slice without clear bounded context	Slices represent bounded contexts — do not create slices for arbitrary grouping.
Circular dependencies between slices	Slices should be acyclic: Slice A imports from Slice B, not vice versa.
Forgetting to register the slice in config/app.rb	The slice must be registered in the app to be mounted.
Duplicating main app configuration	Slices inherit app configuration — only override when necessary.
Defining routes in the main app	Slice routes belong in slices/<name>/config/routes.rb.
Missing smoke tests for slice routes	Always verify the slice mounts and responds at its path.