Added serializer namespacing option

CHANGELOG.md

@@ -5,4 +5,5 @@
   * adds `has_one` attribute for backwards compatibility [@ggordon]
   * updates JSON API support to RC3 [@mateomurphy]
   * adds fragment cache support [@joaomdmoura]
-  * adds cache support to attributes and associations [@joaomdmoura]
+  * adds cache support to attributes and associations [@joaomdmoura]
+  * adds a `:namespace` option to association and array serializer [@groyoh]

README.md

@@ -249,6 +249,16 @@ The `has_many`, `has_one`, and `belongs_to` declarations describe relationships
 resources. By default, when you serialize a `Post`, you will get its `Comment`s
 as well.
 
+You may use the `:namespace` options to specify the `module` where the serializer(s) of an
+association may be found, for example:
+
+```ruby
+  has_many :comments, namespace: Blogging::Serializers
+```
+The serializer used then depends on the class of the object to be serialized e.g. if a
+comment is an instance of class `AdminComment`, the serializer would use
+`Blogging::Serializers::AdminComment` to serializer this comment.
+
 You may also use the `:serializer` option to specify a custom serializer class, for example:
 
 ```ruby
@@ -258,6 +268,20 @@ You may also use the `:serializer` option to specify a custom serializer class,
 The `url` declaration describes which named routes to use while generating URLs
 for your JSON. Not every adapter will require URLs.
 
+## Array serializer
+When calling the `ActiveModel::Serializer::ArraySerializer#new`, you may pass the `:namespace`
+to specify the module in which the objects serializers may be found. The serializers used then
+depend on the objects class.
+
+Take the example below:
+
+```ruby
+a = [Post.new,AdminComment.new]
+ActiveRecord::Serializer.ArraySerializer.new(a, namespace: Blogging::Serializers)
+```
+Here the objects of `a` would respectively be serialized using `Blogging::Serializers::Post`
+and `Blogging::Serializers::AdminComment.`
+
 ## Caching
 
 To cache a serializer, call ```cache``` and pass its options.

lib/active_model/serializer.rb

@@ -118,9 +118,14 @@ def self.serializer_for(resource, options = {})
       if resource.respond_to?(:to_ary)
         config.array_serializer
       else
-        options
-          .fetch(:association_options, {})
-          .fetch(:serializer, get_serializer_for(resource.class))
+        resource_class = resource.class
+        association_options = options.fetch(:association_options, {})
+        namespace = options[:namespace] || association_options[:namespace]
+        if namespace
+          get_namespaced_serializer_for(namespace,resource_class)
+        else
+          association_options.fetch(:serializer, get_serializer_for(resource_class))
+        end
       end
     end
 
@@ -228,8 +233,11 @@ def each_association(&block)
 
     def serializer_from_options(options)
       opts = {}
-      serializer = options.fetch(:association_options, {}).fetch(:serializer, nil)
-      opts[:serializer] = serializer if serializer
+      association_options = options.fetch(:association_options, {})
+      [:serializer,:namespace].each do |key|
+        value = association_options.fetch(key, nil)
+        opts[key] = value if value
+      end
       opts
     end
 
@@ -241,6 +249,19 @@ def self.serializers_cache
 
     attr_reader :options
 
+    def self.get_namespaced_serializer_for(namespace, klass)
+      serializer_class_name = "#{namespace}::#{klass.name.demodulize}"
+      serializers_cache.fetch_or_store(serializer_class_name) do
+        serializer_class = serializer_class_name.safe_constantize
+
+        if serializer_class
+          serializer_class
+        elsif klass.superclass
+          get_namespaced_serializer_for(namespace, klass.superclass)
+        end
+      end
+    end
+
     def self.get_serializer_for(klass)
       serializers_cache.fetch_or_store(klass) do
         serializer_class_name = "#{klass.name}Serializer"

lib/active_model/serializer/array_serializer.rb

@@ -8,11 +8,10 @@ class ArraySerializer
 
       def initialize(objects, options = {})
         options.merge!(root: nil)
-
         @objects = objects.map do |object|
           serializer_class = options.fetch(
             :serializer,
-            ActiveModel::Serializer.serializer_for(object)
+            ActiveModel::Serializer.serializer_for(object, options)
           )
           serializer_class.new(object, options)
         end

test/array_serializer_test.rb

@@ -24,6 +24,18 @@ def test_each_object_should_be_serialized_with_appropriate_serializer
 
         assert_equal serializers.last.custom_options[:some], :options
       end
+
+      def test_each_object_should_be_serialized_with_appropriate_serializer
+        @comment = BasicComment.new
+        @serializer = ArraySerializer.new([@comment, @post], {namespace: Test::Serializer})
+        serializers =  @serializer.to_a
+
+        assert_kind_of Test::Serializer::BasicComment, serializers.first
+        assert_kind_of Comment, serializers.first.object
+
+        assert_kind_of Test::Serializer::Post, serializers.last
+        assert_kind_of Post, serializers.last.object
+      end
     end
   end
 end

test/fixtures/poro.rb

@@ -57,16 +57,18 @@ class ProfilePreviewSerializer < ActiveModel::Serializer
   urls :posts, :comments
 end
 
-Post     = Class.new(Model)
-Like     = Class.new(Model)
-Comment  = Class.new(Model)
-Author   = Class.new(Model)
-Bio      = Class.new(Model)
-Blog     = Class.new(Model)
-Role     = Class.new(Model)
-User = Class.new(Model)
-Location = Class.new(Model)
-Place    = Class.new(Model)
+Post           = Class.new(Model)
+Like           = Class.new(Model)
+Comment        = Class.new(Model)
+BasicComment   = Class.new(Comment)
+SpecialComment = Class.new(Comment)
+Author         = Class.new(Model)
+Bio            = Class.new(Model)
+Blog           = Class.new(Model)
+Role           = Class.new(Model)
+User           = Class.new(Model)
+Location       = Class.new(Model)
+Place          = Class.new(Model)
 
 module Spam; end
 Spam::UnrelatedLink = Class.new(Model)
@@ -204,3 +206,29 @@ def self.root_name
 Spam::UnrelatedLinkSerializer = Class.new(ActiveModel::Serializer) do
   attributes :id
 end
+
+module Test
+  module Serializer
+    Post = Class.new(ActiveModel::Serializer) do
+      attributes :id, :title
+
+      has_many :comments, namespace: Test::Serializer
+    end
+
+    BasicComment = Class.new(ActiveModel::Serializer) do
+      attribute :id
+
+      belongs_to :post, namespace: Test::Serializer
+    end
+
+    SpecialComment = Class.new(ActiveModel::Serializer) do
+      attributes :id, :special
+
+      belongs_to :post, namespace: Test::Serializer
+
+      def special
+        "I'm so special!"
+      end
+    end
+  end
+end

test/serializers/associations_test.rb

@@ -73,6 +73,15 @@ def test_serializer_options_are_passed_into_associations_serializers
         end
       end
 
+      def test_association_with_namespace_options_uses_namespace_serializer
+        @post.comments = [BasicComment.new, SpecialComment.new]
+        @post_serializer = Test::Serializer::Post.new(@post)
+        @post_serializer.each_association do |name, serializer, options|
+          assert_kind_of Test::Serializer::BasicComment, serializer.to_a.first
+          assert_kind_of Test::Serializer::SpecialComment, serializer.to_a.last
+        end
+      end
+
       def test_belongs_to
         assert_equal(
           { post: { type: :belongs_to, association_options: {} },

test/serializers/serializer_for_test.rb

@@ -30,6 +30,9 @@ class SerializerTest <  Minitest::Test
         class MyProfile < Profile
         end
 
+        class TopComment < BasicComment
+        end
+
         def setup
           @profile = Profile.new
           @my_profile = MyProfile.new
@@ -50,6 +53,18 @@ def test_serializer_inherited_serializer
           serializer = ActiveModel::Serializer.serializer_for(@my_profile)
           assert_equal ProfileSerializer, serializer
         end
+
+        def test_serializer_in_module
+          post = Post.new
+          serializer = ActiveModel::Serializer.serializer_for(post, { namespace: Test::Serializer })
+          assert_equal Test::Serializer::Post, serializer
+        end
+
+        def test_serializer_inherited_serializer_in_module
+          comment = TopComment.new
+          serializer = ActiveModel::Serializer.serializer_for(comment, { namespace: Test::Serializer })
+          assert_equal Test::Serializer::BasicComment, serializer
+        end
       end
     end
   end