Fix serialize/deserialize circular entries

Fixes: #204

Author: artofhuman

lib/temporal/json.rb

@@ -5,6 +5,7 @@ module Temporal
   module JSON
     OJ_OPTIONS = {
       mode: :object,
+      circular: true,
       # use ruby's built-in serialization.  If nil, OJ seems to default to ~15 decimal places of precision
       float_precision: 0
     }.freeze

spec/unit/lib/temporal/connection/serializer/failure_spec.rb

@@ -80,7 +80,7 @@ def initialize(message)
       expect(avoids_truncation_error).to eq(old_style_deserialized_error)
     end
 
-    it 'logs a helpful error when the payload is too large' do 
+    it 'logs a helpful error when the payload is too large' do
       e = MyBigError.new('Uh oh!')
 
       allow(Temporal.logger).to receive(:error)
@@ -90,10 +90,9 @@ def initialize(message)
         .to have_received(:error)
         .with(
           "Could not serialize exception because it's too large, so we are using a fallback that may not deserialize "\
-          "correctly on the client.  First #{max_bytes} bytes:\n{\"^o\":\"MyBigError\",\"big_payload\":\"1234567890123456",
+          "correctly on the client.  First #{max_bytes} bytes:\n{\"^o\":\"MyBigError\",\"^i\":1,\"big_payload\":\"123456789",
           { unserializable_error: 'MyBigError' }
         )
-
     end
 
     class MyArglessError < RuntimeError

spec/unit/lib/temporal/json.rb

@@ -2,12 +2,25 @@
 
 describe Temporal::JSON do
   let(:hash) { { 'one' => 'one', two: :two, ':three' => ':three' } }
-  let(:json) { '{"one":"one",":two":":two","\u003athree":"\u003athree"}' }
+  let(:json) { '{"^i":1,"one":"one",":two":":two","\u003athree":"\u003athree"}' }
 
   describe '.serialize' do
     it 'generates JSON string' do
       expect(described_class.serialize(hash)).to eq(json)
     end
+
+    it 'does not raise error on circular entries' do
+      author = Struct.new('Author', :name, :books)
+      book = Struct.new('Book', :author)
+      author_entry = author.new(name: 'David')
+      book_entry = book.new(title: 'test', author: author)
+
+      author_entry.books = [book_entry]
+      json = described_class.serialize(author_entry)
+
+      result = described_class.deserialize(json)
+      expect(result).to eq(author_entry)
+    end
   end
 
   describe '.deserialize' do