From 4ad9c64e46dbd7766726d0a013934b30ba4fdbc8 Mon Sep 17 00:00:00 2001
From: Yehuda Katz <wycats@gmail.com>
Date: Wed, 11 Jan 2012 20:56:36 -0700
Subject: [PATCH] Allow serializers to receive instructions to explicitly
 include or exclude specific lists of associations.

---
 lib/active_model/serializer.rb | 18 +++++++-
 test/association_test.rb       | 84 ++++++++++++++++++++++++++++++++++
 2 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index f601a409..1ba94bec 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -372,7 +372,23 @@ module ActiveModel
 
     def include_associations!(node)
       _associations.each do |attr, klass|
-        include! attr, :node => node
+        opts = { :node => node }
+
+        if options.include?(:include) || options.include?(:exclude)
+          opts[:include] = included_association?(attr)
+        end
+
+        include! attr, opts
+      end
+    end
+
+    def included_association?(name)
+      if options.key?(:include)
+        options[:include].include?(name)
+      elsif options.key?(:exclude)
+        !options[:exclude].include?(name)
+      else
+        true
       end
     end
 
diff --git a/test/association_test.rb b/test/association_test.rb
index dcb8d53e..b8687b33 100644
--- a/test/association_test.rb
+++ b/test/association_test.rb
@@ -305,4 +305,88 @@ class AssociationTest < ActiveModel::TestCase
       }, @root_hash)
     end
   end
+
+  class InclusionTest < AssociationTest
+    def setup
+      super
+
+      comment_serializer_class = @comment_serializer_class
+
+      @post_serializer_class.class_eval do
+        root :post
+        embed :ids, :include => true
+        has_many :comments, :serializer => comment_serializer_class
+      end
+    end
+
+    def test_when_it_is_included
+      post_serializer = @post_serializer_class.new(
+        @post, nil, :include => [:comments]
+      )
+
+      json = post_serializer.as_json
+
+      assert_equal({
+        :post => {
+          :title => "New Post",
+          :body => "Body",
+          :comments => [ 1 ]
+        },
+        :comments => [
+          { :id => 1, :body => "ZOMG A COMMENT" }
+        ]
+      }, json)
+    end
+
+    def test_when_it_is_not_included
+      post_serializer = @post_serializer_class.new(
+        @post, nil, :include => []
+      )
+
+      json = post_serializer.as_json
+
+      assert_equal({
+        :post => {
+          :title => "New Post",
+          :body => "Body",
+          :comments => [ 1 ]
+        }
+      }, json)
+    end
+
+    def test_when_it_is_excluded
+      post_serializer = @post_serializer_class.new(
+        @post, nil, :exclude => [:comments]
+      )
+
+      json = post_serializer.as_json
+
+      assert_equal({
+        :post => {
+          :title => "New Post",
+          :body => "Body",
+          :comments => [ 1 ]
+        }
+      }, json)
+    end
+
+    def test_when_it_is_not_excluded
+      post_serializer = @post_serializer_class.new(
+        @post, nil, :exclude => []
+      )
+
+      json = post_serializer.as_json
+
+      assert_equal({
+        :post => {
+          :title => "New Post",
+          :body => "Body",
+          :comments => [ 1 ]
+        },
+        :comments => [
+          { :id => 1, :body => "ZOMG A COMMENT" }
+        ]
+      }, json)
+    end
+  end
 end