Merge pull request #285 from seratch/feature/issue137

Fix #137 Make DefaultFormats serializable

core/src/main/scala/org/json4s/Formats.scala

@@ -37,7 +37,7 @@ object Formats {
 @implicitNotFound(
   "No org.json4s.Formats found. Try to bring an instance of org.json4s.Formats in scope or use the org.json4s.DefaultFormats."
 )
-trait Formats { self: Formats =>
+trait Formats extends Serializable { self: Formats =>
   def dateFormat: DateFormat
   def typeHints: TypeHints = NoTypeHints
   def customSerializers: List[Serializer[_]] = Nil

tests/src/test/scala/org/json4s/FormatsSpec.scala

@@ -0,0 +1,21 @@
+package org.json4s
+
+import org.specs2.mutable.Specification
+
+class FormatsSpec extends Specification {
+
+  "Formats" should {
+    "be a Serializable" in {
+      val f = new Formats {
+        def dateFormat: DateFormat = ???
+      }
+      f.isInstanceOf[Serializable] must beTrue
+    }
+  }
+
+  "DefaultFormats" should {
+    "be a Serializable" in {
+      DefaultFormats.isInstanceOf[Serializable] must beTrue
+    }
+  }
+}