Improved integration with Global ID

Implementing `Decorator.find` improves compatibility with Global ID and
allows one to use decorated objects in jobs seamlessly.

Resolves #663.
Improves #817.

README.md

@@ -652,9 +652,8 @@ you can include this module manually.
 [Active Job](http://edgeguides.rubyonrails.org/active_job_basics.html) allows you to pass ActiveRecord
 objects to background tasks directly and performs the necessary serialization and deserialization. In
 order to do this, arguments to a background job must implement [Global ID](https://github.com/rails/globalid).
-Decorated objects implement Global ID by delegating to the object they are decorating. This means
-you can pass decorated objects to background jobs, however, the object won't be decorated when it is
-deserialized.
+Decorators implement Global ID.
+This means you can pass decorated objects to background jobs, and get them just as decorated when deserialized.
 
 ## Contributors
 

lib/draper/compatibility/global_id.rb

@@ -5,17 +5,21 @@ module Compatibility
     # and deserialization. In order to do this, arguments to a background job must implement
     # [Global ID](https://github.com/rails/globalid).
     #
-    # This compatibility patch implements Global ID for decorated objects by delegating to the object
-    # that is decorated. This means you can pass decorated objects to background jobs, but 
-    # the object won't be decorated when it is deserialized. This patch is meant as an intermediate
-    # fix until we can find a way to deserialize the decorated object correctly.
+    # This compatibility patch implements Global ID for decorated objects by defining `.find(id)`
+    # class method that uses the original one and decorates the result.
+    # This means you can pass decorated objects to background jobs and they will be decorated when
+    # deserialized.
     module GlobalID
       extend ActiveSupport::Concern
 
       included do
         include ::GlobalID::Identification
+      end
 
-        delegate :to_global_id, :to_signed_global_id, to: :object
+      class_methods do
+        def find(*args)
+          object_class.find(*args).decorate
+        end
       end
     end
   end

spec/dummy/spec/decorators/post_decorator_spec.rb

@@ -61,4 +61,13 @@
   it "uses a test view context from BaseController" do
     expect(Draper::ViewContext.current.controller).to be_an BaseController
   end
+
+  describe 'Global ID' do
+    it { expect(GlobalID::Locator.locate decorator.to_gid).to eq decorator }
+    it { expect(GlobalID::Locator.locate decorator.to_gid).to be_decorated }
+    it { expect(GlobalID::Locator.locate object.to_gid).not_to be_decorated }
+    it { expect(GlobalID::Locator.locate_signed decorator.to_sgid).to eq decorator }
+    it { expect(GlobalID::Locator.locate_signed decorator.to_sgid).to be_decorated }
+    it { expect(GlobalID::Locator.locate_signed object.to_sgid).not_to be_decorated }
+  end
 end

spec/dummy/spec/jobs/publish_post_job_spec.rb

@@ -4,6 +4,8 @@
   subject(:job) { described_class.perform_later(post) }
 
   it 'queues the job' do
-    expect { job }.to have_enqueued_job(described_class).with(post.object)
+    expect { job }.to have_enqueued_job(described_class).with { |post|
+      expect(post).to be_decorated
+    }
   end
 end

spec/dummy/spec/models/post_spec.rb

@@ -5,11 +5,4 @@
   it_behaves_like 'a decoratable model'
 
   it { should be_a ApplicationRecord }
-
-  describe '#to_global_id' do
-    let(:post) { Post.create }
-    subject { post.to_global_id }
-
-    it { is_expected.to eq post.decorate.to_global_id }
-  end
 end