Namespace inferred serializer resolution.

.rubocop.yml

@@ -1,5 +1,9 @@
 inherit_from: .rubocop_todo.yml
+
 AllCops:
   Exclude:
     - Guardfile
     - grape-active_model_serializers.gemspec
+
+Style/BlockDelimiters:
+  Enabled: false

.rubocop_todo.yml

@@ -18,7 +18,3 @@ Style/Documentation:
 # Configuration parameters: Exclude.
 Style/FileName:
   Enabled: false
-
-# Offense count: 4
-Style/RegexpLiteral:
-  MaxSlashes: 0

grape-active_model_serializers.gemspec

@@ -24,5 +24,5 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency 'rack-test'
   gem.add_development_dependency 'rake'
   gem.add_development_dependency 'guard-rspec'
-  gem.add_development_dependency 'rubocop', '0.28.0'
+  gem.add_development_dependency 'rubocop'
 end

lib/grape-active_model_serializers/endpoint_extension.rb

@@ -9,7 +9,7 @@ module Grape
     attr_accessor :controller_name
 
     def namespace_options
-      if self.respond_to?(:inheritable_setting)
+      if respond_to?(:inheritable_setting)
         inheritable_setting.namespace
       else
         settings[:namespace] ? settings[:namespace].options : {}
@@ -17,7 +17,7 @@ module Grape
     end
 
     def route_options
-      if self.respond_to?(:inheritable_setting)
+      if respond_to?(:inheritable_setting)
         inheritable_setting.route
       else
         options[:route_options]

lib/grape-active_model_serializers/options_builder.rb

@@ -9,7 +9,7 @@ module Grape
       def options
         @options ||= (
           options = endpoint_options
-          options.merge!(scope: endpoint) unless options.key?(:scope)
+          options[:scope] = endpoint unless options.key?(:scope)
           options.merge!(default_root_options) unless options.key?(:root)
           options.merge!(meta_options)
           options

lib/grape-active_model_serializers/serializer_resolver.rb

@@ -8,7 +8,7 @@ module Grape
 
       def serializer
         @serializer ||= (
-          serializer_klass.new(resource, options) if serializer_klass
+          serializer_class.new(resource, options) if serializer_class
         )
       end
 
@@ -16,26 +16,57 @@ module Grape
 
       attr_accessor :resource, :options
 
-      def serializer_klass
-        serializer_klass = options[:serializer]
-        serializer_klass ||= namespaced_resource_serializer_klass
-        serializer_klass
+      def serializer_class
+        serializer_class = resource_defined_class
+        serializer_class ||= collection_class
+        serializer_class ||= options[:serializer]
+        serializer_class ||= namespace_inferred_class
+        serializer_class ||= version_inferred_class
+        serializer_class ||= resource_serializer_class
+        serializer_class
       end
 
-      def namespaced_resource_serializer_klass
-        "#{namespace}::#{resource_serializer_klass}".constantize
-      rescue NameError
-        resource_serializer_klass
+      def resource_defined_class
+        resource.serializer_class if resource.respond_to?(:serializer_class)
       end
 
-      def namespace
+      def collection_class
+        return nil unless resource.respond_to?(:to_ary)
+        ActiveModel::Serializer.config.collection_serializer
+      end
+
+      def namespace_inferred_class
+        return nil unless options[:for]
+        namespace = options[:for].to_s.deconstantize
+        "#{namespace}::#{resource_serializer_klass}".safe_constantize
+      end
+
+      def version_inferred_class
+        "#{version}::#{resource_serializer_klass}".safe_constantize
+      end
+
+      def version
         options[:version].try(:classify)
       end
 
       def resource_serializer_klass
-        @resource_serializer_klass ||= ActiveModel::Serializer.serializer_for(
-          resource
-        )
+        @resource_serializer_klass ||= [
+          resource_namespace,
+          "#{resource_klass}Serializer"
+        ].compact.join('::')
+      end
+
+      def resource_klass
+        resource.class.name.demodulize
+      end
+
+      def resource_namespace
+        klass = resource.class.name.deconstantize
+        klass.empty? ? nil : klass
+      end
+
+      def resource_serializer_class
+        ActiveModel::Serializer.serializer_for(resource)
       end
     end
   end

lib/grape-active_model_serializers/version.rb

@@ -1,5 +1,5 @@
 module Grape
   module ActiveModelSerializers
-    VERSION = '1.4.0'
+    VERSION = '1.4.0'.freeze
   end
 end

spec/grape/active_model_serializers/serializer_resolver_spec.rb

@@ -0,0 +1,102 @@
+require 'spec_helper'
+
+# asserts serializer resolution order:
+#   1. resource_defined_class     # V1::UserSerializer
+#   2. collection_class           # CollectionSerializer
+#   3. options[:serializer]       # V2::UserSerializer
+#   4. namespace_inferred_class   # V3::UserSerializer
+#   5. version_inferred_class     # V4::UserSerializer
+#   6. resource_serializer_class  # UserSerializer
+#   7. missing resource           # nil
+
+describe Grape::ActiveModelSerializers::SerializerResolver do
+  let(:resolver) { described_class.new(resource, options) }
+  let(:resource) { User.new }
+  let(:options) {
+    {
+      serializer: options_serializer_class, # options defined
+      for:        V3::UsersApi,             # namespace inference
+      version:    'v4'                      # version inference
+    }
+  }
+  # resource defined
+  let(:resource_defined?) { true }
+  let(:defined_serializer_class) { V1::UserSerializer }
+  # options defined
+  let(:options_serializer_class) { V2::UserSerializer }
+
+  let(:serializer) { resolver.serializer }
+
+  before do
+    if resource_defined?
+      allow(resource).to receive(:respond_to?).and_call_original
+      allow(resource).to receive(:respond_to?).with(:to_ary) { true }
+      allow(resource).to receive(:serializer_class) { defined_serializer_class }
+    end
+  end
+
+  context 'resource defined' do
+    it 'returns serializer' do
+      expect(serializer).to be_kind_of(defined_serializer_class)
+    end
+  end
+
+  context 'not resource defined' do
+    let(:resource_defined?) { false }
+
+    context 'resource collection' do
+      let(:resource) { [User.new] }
+      let(:serializer_class) { ActiveModel::Serializer::CollectionSerializer }
+
+      it 'returns serializer' do
+        expect(serializer).to be_kind_of(serializer_class)
+      end
+    end
+
+    context 'not resource collection' do
+      context 'specified by options' do
+        it 'returns specified serializer' do
+          expect(serializer).to be_kind_of(V2::UserSerializer)
+        end
+      end
+
+      context 'not specified by options' do
+        let(:options) { super().except(:serializer) }
+
+        context 'namespace inferred' do
+          it 'returns inferred serializer' do
+            expect(serializer).to be_kind_of(V3::UserSerializer)
+          end
+        end
+
+        context 'not namespace inferred' do
+          let(:options) { super().except(:for) }
+
+          context 'version inferred' do
+            it 'returns inferred serializer' do
+              expect(serializer).to be_kind_of(V4::UserSerializer)
+            end
+          end
+
+          context 'not version inferred' do
+            let(:options) { super().except(:version) }
+
+            context 'ASM resolved' do
+              it 'returns serializer' do
+                expect(serializer).to be_kind_of(UserSerializer)
+              end
+            end
+
+            context 'not ASM resolved' do
+              let(:resource) { nil }
+
+              it 'returns nil' do
+                expect(serializer).to eq(nil)
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/support/api/users_api.rb

@@ -0,0 +1,13 @@
+class UsersApi < Grape::API
+  resource :users do
+    desc 'all users'
+    get do
+      [User.new]
+    end
+
+    desc 'specified user'
+    get '/:id' do
+      User.new
+    end
+  end
+end

spec/support/api/v3/users_api.rb

@@ -0,0 +1,15 @@
+module V3
+  class UsersApi < Grape::API
+    resource :users do
+      desc 'all users'
+      get do
+        [User.new]
+      end
+
+      desc 'specified user'
+      get '/:id' do
+        User.new
+      end
+    end
+  end
+end

spec/support/serializers/v2/user_serializer.rb

@@ -0,0 +1,5 @@
+module V2
+  class UserSerializer < ActiveModel::Serializer
+    attributes :first_name, :last_name, :email
+  end
+end

spec/support/serializers/v3/user_serializer.rb

@@ -0,0 +1,5 @@
+module V3
+  class UserSerializer < ActiveModel::Serializer
+    attributes :first_name, :last_name, :email
+  end
+end

spec/support/serializers/v4/user_serializer.rb

@@ -0,0 +1,5 @@
+module V4
+  class UserSerializer < ActiveModel::Serializer
+    attributes :first_name, :last_name, :email
+  end
+end