Adding Fragment Cache to AMS

It's an upgrade based on the new Cache implementation #693.
It allows to use the Rails conventions to cache
specific attributes or associations.
It's based on the Cache Composition implementation.

test/serializers/cache_test.rb

@@ -3,21 +3,33 @@ module ActiveModel
   class Serializer
     class CacheTest < Minitest::Test
       def setup
-        @post            = Post.new({ title: 'New Post', body: 'Body' })
-        @comment         = Comment.new({ id: 1, body: 'ZOMG A COMMENT' })
-        @author          = Author.new(name: 'Joao M. D. Moura')
-        @role            = Role.new(name: 'Great Author')
-        @author.posts    = [@post]
-        @author.roles    = [@role]
-        @author.bio      = nil
-        @post.comments   = [@comment]
-        @post.author     = @author
-        @comment.post    = @post
-        @comment.author  = @author
+        ActionController::Base.cache_store.clear
+        @comment        = Comment.new(id: 1, body: 'ZOMG A COMMENT')
+        @blog           = Blog.new(id: 999, name: "Custom blog")
+        @post           = Post.new(title: 'New Post', body: 'Body')
+        @bio            = Bio.new(id: 1, content: 'AMS Contributor')
+        @author         = Author.new(name: 'Joao M. D. Moura')
+        @role           = Role.new(name: 'Great Author')
+        @location       = Location.new(lat: '-23.550520', lng: '-46.633309')
+        @place          = Place.new(name: 'Amazing Place')
+        @author.posts   = [@post]
+        @author.roles   = [@role]
+        @role.author    = @author
+        @author.bio     = @bio
+        @bio.author     = @author
+        @post.comments  = [@comment]
+        @post.author    = @author
+        @comment.post   = @post
+        @comment.author = @author
+        @post.blog      = @blog
+        @location.place = @place
 
-        @post_serializer    = PostSerializer.new(@post)
-        @author_serializer  = AuthorSerializer.new(@author)
-        @comment_serializer = CommentSerializer.new(@comment)
+        @location_serializer = LocationSerializer.new(@location)
+        @bio_serializer      = BioSerializer.new(@bio)
+        @role_serializer     = RoleSerializer.new(@role)
+        @post_serializer     = PostSerializer.new(@post)
+        @author_serializer   = AuthorSerializer.new(@author)
+        @comment_serializer  = CommentSerializer.new(@comment)
       end
 
       def test_cache_definition
@@ -33,28 +45,82 @@ module ActiveModel
       end
 
       def test_cache_key_interpolation_with_updated_at
-        author = render_object_with_cache_without_cache_key(@author)
+        author = render_object_with_cache(@author)
         assert_equal(nil, ActionController::Base.cache_store.fetch(@author.cache_key))
-        assert_equal(author, ActionController::Base.cache_store.fetch("#{@author_serializer.class._cache_key}/#{@author_serializer.object.id}-#{@author_serializer.object.updated_at}").to_json)
+        assert_equal(@author_serializer.attributes.to_json, ActionController::Base.cache_store.fetch("#{@author_serializer.class._cache_key}/#{@author_serializer.object.id}-#{@author_serializer.object.updated_at}").to_json)
       end
 
       def test_default_cache_key_fallback
-        comment = render_object_with_cache_without_cache_key(@comment)
-        assert_equal(comment, ActionController::Base.cache_store.fetch(@comment.cache_key).to_json)
+        comment = render_object_with_cache(@comment)
+        assert_equal(@comment_serializer.attributes.to_json, ActionController::Base.cache_store.fetch(@comment.cache_key).to_json)
       end
 
       def test_cache_options_definition
-        assert_equal({expires_in: 0.05}, @post_serializer.class._cache_options)
+        assert_equal({expires_in: 0.1}, @post_serializer.class._cache_options)
         assert_equal(nil, @author_serializer.class._cache_options)
         assert_equal({expires_in: 1.day}, @comment_serializer.class._cache_options)
       end
 
+      def test_fragment_cache_definition
+        assert_equal([:name], @role_serializer.class._cache_only)
+        assert_equal([:content], @bio_serializer.class._cache_except)
+      end
+
+      def test_associations_separately_cache
+        ActionController::Base.cache_store.clear
+        assert_equal(nil, ActionController::Base.cache_store.fetch(@post.cache_key))
+        assert_equal(nil, ActionController::Base.cache_store.fetch(@comment.cache_key))
+
+        post = render_object_with_cache(@post)
+
+        assert_equal(@post_serializer.attributes, ActionController::Base.cache_store.fetch(@post.cache_key))
+        assert_equal(@comment_serializer.attributes, ActionController::Base.cache_store.fetch(@comment.cache_key))
+      end
+
+      def test_associations_cache_when_updated
+        # Clean the Cache
+        ActionController::Base.cache_store.clear
+
+        # Generate a new Cache of Post object and each objects related to it.
+        render_object_with_cache(@post)
+
+        # Check if if cache the objects separately
+        assert_equal(@post_serializer.attributes, ActionController::Base.cache_store.fetch(@post.cache_key))
+        assert_equal(@comment_serializer.attributes, ActionController::Base.cache_store.fetch(@comment.cache_key))
+
+        # Simulating update on comments relationship with Post
+        new_comment            = Comment.new(id: 2, body: 'ZOMG A NEW COMMENT')
+        new_comment_serializer = CommentSerializer.new(new_comment)
+        @post.comments         = [new_comment]
+
+        # Ask for the serialized object
+        render_object_with_cache(@post)
+
+        # Check if the the new comment was cached
+        assert_equal(new_comment_serializer.attributes, ActionController::Base.cache_store.fetch(new_comment.cache_key))
+        assert_equal(@post_serializer.attributes, ActionController::Base.cache_store.fetch(@post.cache_key))
+      end
+
+      def test_fragment_fetch_with_virtual_associations
+        expected_result = {
+          id: @location.id,
+          lat: @location.lat,
+          lng: @location.lng,
+          place: 'Nowhere'
+        }
+
+        hash = render_object_with_cache(@location)
+
+        assert_equal(hash, expected_result)
+        assert_equal({place: 'Nowhere'}, ActionController::Base.cache_store.fetch(@location.cache_key))
+      end
+
       private
-      def render_object_with_cache_without_cache_key(obj)
+      def render_object_with_cache(obj)
         serializer_class = ActiveModel::Serializer.serializer_for(obj)
         serializer = serializer_class.new(obj)
         adapter = ActiveModel::Serializer.adapter.new(serializer)
-        adapter.to_json
+        adapter.serializable_hash
       end
     end
   end

test/serializers/meta_test.rb

@@ -4,6 +4,7 @@ module ActiveModel
   class Serializer
     class MetaTest < Minitest::Test
       def setup
+        ActionController::Base.cache_store.clear
         @blog = Blog.new(id: 1,
                          name: 'AMS Hints',
                          writer: Author.new(id: 2, name: "Steve"),