Associations refactoring

* Move all associations related code from Serializer class to Associations module
* Introduce Reflection class hierarchy
* Introduce Association class
* Rid off Serializer#each_association
* Introduce Serializer#associations enumerator

test/serializers/association_macros_test.rb

@@ -0,0 +1,36 @@
+require 'test_helper'
+
+module ActiveModel
+  class Serializer
+    class AssociationMacrosTest < Minitest::Test
+      AuthorSummarySerializer = Class.new
+      class AssociationsTestSerializer < Serializer
+        belongs_to :author, serializer: AuthorSummarySerializer
+        has_many :comments, embed: :ids
+        has_one :category
+      end
+
+      def before_setup
+        @reflections = AssociationsTestSerializer._reflections
+      end
+
+      def test_has_one_defines_reflection
+        has_one_reflection = HasOneReflection.new(:category, {})
+
+        assert_includes(@reflections, has_one_reflection)
+      end
+
+      def test_has_many_defines_reflection
+        has_many_reflection = HasManyReflection.new(:comments, embed: :ids)
+
+        assert_includes(@reflections, has_many_reflection)
+      end
+
+      def test_belongs_to_defines_reflection
+        belongs_to_reflection = BelongsToReflection.new(:author, serializer: AuthorSummarySerializer)
+
+        assert_includes(@reflections, belongs_to_reflection)
+      end
+    end
+  end
+end

test/serializers/associations_test.rb

@@ -45,21 +45,20 @@ module ActiveModel
       end
 
       def test_has_many_and_has_one
-        assert_equal(
-          { posts: { type: :has_many, association_options: { embed: :ids } },
-            roles: { type: :has_many, association_options: { embed: :ids } },
-            bio: { type: :has_one, association_options: {} } },
-          @author_serializer.class._associations
-        )
-        @author_serializer.each_association do |key, serializer, options|
-          if key == :posts
-            assert_equal({embed: :ids}, options)
+        @author_serializer.associations.each do |association|
+          key = association.key
+          serializer = association.serializer
+          options = association.options
+
+          case key
+          when :posts
+            assert_equal({ embed: :ids }, options)
             assert_kind_of(ActiveModel::Serializer.config.array_serializer, serializer)
-          elsif key == :bio
+          when :bio
             assert_equal({}, options)
             assert_nil serializer
-          elsif key == :roles
-            assert_equal({embed: :ids}, options)
+          when :roles
+            assert_equal({ embed: :ids }, options)
             assert_kind_of(ActiveModel::Serializer.config.array_serializer, serializer)
           else
             flunk "Unknown association: #{key}"
@@ -68,7 +67,11 @@ module ActiveModel
       end
 
       def test_has_many_with_no_serializer
-        PostWithTagsSerializer.new(@post).each_association do |key, serializer, options|
+        PostWithTagsSerializer.new(@post).associations.each do |association|
+          key = association.key
+          serializer = association.serializer
+          options = association.options
+
           assert_equal key, :tags
           assert_equal serializer, nil
           assert_equal [{ attributes: { name: "#hashtagged" }}].to_json, options[:virtual_value].to_json
@@ -76,70 +79,67 @@ module ActiveModel
       end
 
       def test_serializer_options_are_passed_into_associations_serializers
-        @post_serializer.each_association do |key, association|
-          if key == :comments
-            assert association.first.custom_options[:custom_options]
-          end
-        end
+        association = @post_serializer
+                        .associations
+                        .detect { |association| association.key == :comments }
+
+        assert association.serializer.first.custom_options[:custom_options]
       end
 
       def test_belongs_to
-        assert_equal(
-          { post: { type: :belongs_to, association_options: {} },
-            author: { type: :belongs_to, association_options: {} } },
-          @comment_serializer.class._associations
-        )
-        @comment_serializer.each_association do |key, serializer, options|
-          if key == :post
-            assert_equal({}, options)
+        @comment_serializer.associations.each do |association|
+          key = association.key
+          serializer = association.serializer
+
+          case key
+          when :post
             assert_kind_of(PostSerializer, serializer)
-          elsif key == :author
-            assert_equal({}, options)
+          when :author
             assert_nil serializer
           else
             flunk "Unknown association: #{key}"
           end
+
+          assert_equal({}, association.options)
         end
       end
 
       def test_belongs_to_with_custom_method
-        blog_is_present = false
-
-        @post_serializer.each_association do |key, serializer, options|
-          blog_is_present = true if key == :blog
-        end
-
-        assert blog_is_present
+        assert(
+          @post_serializer.associations.any? do |association|
+            association.key == :blog
+          end
+        )
       end
 
       def test_associations_inheritance
         inherited_klass = Class.new(PostSerializer)
 
-        assert_equal(PostSerializer._associations, inherited_klass._associations)
+        assert_equal(PostSerializer._reflections, inherited_klass._reflections)
       end
 
       def test_associations_inheritance_with_new_association
         inherited_klass = Class.new(PostSerializer) do
           has_many :top_comments, serializer: CommentSerializer
         end
-        expected_associations = PostSerializer._associations.merge(
-          top_comments: {
-            type: :has_many,
-            association_options: {
-              serializer: CommentSerializer
-            }
-          }
+
+        assert(
+          PostSerializer._reflections.all? do |reflection|
+            inherited_klass._reflections.include?(reflection)
+          end
+        )
+
+        assert(
+          inherited_klass._reflections.any? do |reflection|
+            reflection.name == :top_comments
+          end
         )
-        assert_equal(inherited_klass._associations, expected_associations)
       end
 
       def test_associations_custom_keys
         serializer = PostWithCustomKeysSerializer.new(@post)
 
-        expected_association_keys = []
-        serializer.each_association do |key, serializer, options|
-          expected_association_keys << key
-        end
+        expected_association_keys = serializer.associations.map(&:key)
 
         assert expected_association_keys.include? :reviews
         assert expected_association_keys.include? :writer