Allow using callable objects as scopes #261

docs/scoping.md

@@ -37,6 +37,29 @@ class PostPolicy < ApplicationPolicy
 end
 ```
 
+Or just pass class name where included logic of scope to `relation_scope` and write `.call` method:
+
+```ruby
+class PostsController < ApplicationController
+  def index
+    @posts = authorized_scope(Post.all)
+  end
+end
+
+class PostPolicy < ApplicationPolicy
+  relation_scope AuthorizedPosts
+end
+
+class AuthorizedPosts
+  class << self
+    def call(policy, relation)
+      user = policy.user
+      user.admin? ? relation : relation.where(user: user)
+    end
+  end
+end
+```
+
 ## Define scopes
 
 To define scope you should use either `scope_for` or `smth_scope` methods in your policy:

lib/action_policy/policy/scoping.rb

@@ -113,8 +113,11 @@ def lookup_type_from_target(target)
 
       module ClassMethods # :nodoc:
         # Register a new scoping method for the `type`
-        def scope_for(type, name = :default, &block)
+        def scope_for(type, name = :default, callable = nil, &block)
+          name, callable = prepare_args(name, callable)
+
           mid = :"__scoping__#{type}__#{name}"
+          block = ->(target) { callable.call(self, target) } if callable
 
           define_method(mid, &block)
 
@@ -154,6 +157,14 @@ def scope_matchers
             []
           end
         end
+
+        private
+
+        def prepare_args(name, callable)
+          return [name, callable] if name && callable
+          return [name, nil] if name.is_a?(Symbol) || name.is_a?(String)
+          [:default, name]
+        end
       end
     end
   end

test/action_policy/rails/scope_matchers_test.rb

@@ -154,6 +154,96 @@ def test_named_filtered_params_admin
   end
 end
 
+class TestRailsScopeMatchersViaClass < ActionController::TestCase
+  class AuthorizedPosts
+    class << self
+      def call(policy, relation)
+        user = policy.user
+        scope = user.admin? ? relation : relation.where(user: user)
+        scope.order(:title)
+      end
+    end
+  end
+
+  class PostPolicy < ActionPolicy::Base
+    relation_scope AuthorizedPosts
+  end
+
+  class PostsController < ActionController::Base
+    authorize :user, through: :current_user
+
+    def index
+      render json: authorized_scope(AR::Post.all)
+    end
+
+    private
+
+    def current_user
+      @current_user ||= AR::User.find(params[:user_id])
+    end
+  end
+
+  tests PostsController
+
+  attr_reader :admin, :guest
+
+  def setup
+    ActiveRecord::Base.connection.begin_transaction(joinable: false)
+    @guest = AR::User.create!(name: "Jack")
+    @admin = AR::User.create!(name: "John", role: "admin")
+  end
+
+  def teardown
+    ActiveRecord::Base.connection.rollback_transaction
+  end
+
+  def json_body
+    @json_body ||= JSON.parse(response.body)
+  end
+
+  def test_authorized_relation_guest
+    get :index, params: {user_id: guest.id}
+
+    assert_equal 0, json_body.size
+  end
+
+  def test_authorized_relation_admin
+    get :index, params: {user_id: admin.id}
+
+    assert_equal 0, json_body.size
+  end
+
+  def test_authorized_association
+    AR::Post.create!(title: "[wip]", user: admin)
+    AR::Post.create!(title: "Good news!", user: guest)
+
+    get :index, params: {user_id: guest.id}
+
+    assert_equal 1, json_body.size
+    assert_equal "Good news!", json_body.first["title"]
+  end
+
+  def test_authorized_association_2
+    AR::Post.create!(title: "[wip]", user: admin)
+    AR::Post.create!(title: "Good news!", user: guest)
+
+    get :index, params: {user_id: admin.id}
+
+    assert_equal 2, json_body.size
+    assert_equal ["Good news!", "[wip]"], json_body.map { _1["title"] }
+  end
+
+  def test_authorized_association_3
+    AR::Post.create!(title: "[wip]", user: guest)
+    AR::Post.create!(title: "Admin news", user: admin)
+    AR::Post.create!(title: "Good news!", user: guest)
+
+    get :index, params: {user_id: guest.id}
+
+    assert_equal 2, json_body.size
+  end
+end
+
 # See https://github.com/palkan/action_policy/issues/101
 class TestRelationMutability < ActionController::TestCase
   class UserPolicy < ActionPolicy::Base