@jsonstrict to always use Play's default format

Author: martinraison

README.md

@@ -29,6 +29,8 @@ If the case class contains 2 fields or more, Play's [JSON macro inception](http:
 
 This is often more convenient than Play's default format ```{"name": "San Francisco"}```.
 
+If you would rather stick to Play's default format even for single field case classes, you can use ```@jsonstrict``` instead of ```@json```.
+
 #Installation
 
 If you're using Play (version 2.1 or higher) with SBT, you should add the following settings to your build:

src/main/scala/com/kifi/macros/JsonFormatAnnotation.scala

@@ -6,6 +6,9 @@ import scala.annotation.StaticAnnotation
 
 import CrossVersionDefs._
 
+object jsonMacroInstance extends jsonMacro(false)
+object jsonStrictMacroInstance extends jsonMacro(true)
+
 /**
  * "@json" macro annotation for case classes
  *
@@ -21,10 +24,24 @@ import CrossVersionDefs._
  * then A(4) will be serialized as '4' instead of '{"value": 4}'.
  */
 class json extends StaticAnnotation {
-  def macroTransform(annottees: Any*): Any = macro jsonMacro.impl
+  def macroTransform(annottees: Any*): Any = macro jsonMacroInstance.impl
+}
+
+/**
+ * "@jsonstrict" macro annotation for case classes
+ *
+ * Same as "@json" annotation, except that it always uses the default Play formatter.
+ * For example, if A is defined as:
+ *
+ *     case class A(value: Int)
+ *
+ * then A(4) will be serialized as '{"value": 4}'.
+ */
+class jsonstrict extends StaticAnnotation {
+  def macroTransform(annottees: Any*): Any = macro jsonStrictMacroInstance.impl
 }
 
-object jsonMacro {
+class jsonMacro(isStrict: Boolean) {
   def impl(c: CrossVersionContext)(annottees: c.Expr[Any]*): c.Expr[Any] = {
     import c.universe._
 
@@ -40,8 +57,8 @@ object jsonMacro {
     def jsonFormatter(className: TypeName, fields: List[ValDef]) = {
       fields.length match {
         case 0 => c.abort(c.enclosingPosition, "Cannot create json formatter for case class with no fields")
-        case 1 =>
-          // Only one field, use the serializer for the field
+        case 1 if !isStrict => {
+          // use the serializer for the field
           q"""
             implicit val jsonAnnotationFormat = {
               import play.api.libs.json._
@@ -51,9 +68,11 @@ object jsonMacro {
               )
             }
           """
-        case _ =>
-          // More than one field, use Play's macro
+        }
+        case _ => {
+          // use Play's macro
           q"implicit val jsonAnnotationFormat = play.api.libs.json.Json.format[$className]"
+        }
       }
     }
 

src/test/scala/com/kifi/macros/JsonFormatAnnotationTest.scala

@@ -4,9 +4,11 @@ import org.specs2.mutable.Specification
 import play.api.libs.json._
 
 @json case class City(name: String)
-
 @json case class Person(name: String, age: Int)
 
+@jsonstrict case class City2(name: String)
+@jsonstrict case class Person2(name: String, age: Int)
+
 class JsonFormatAnnotationTest extends Specification {
 
   "@json annotation" should {
@@ -16,7 +18,7 @@ class JsonFormatAnnotationTest extends Specification {
       val city = City("San Francisco")
       val json = Json.toJson(city)
       json === JsString("San Francisco")
-      Json.fromJson[City](json) === JsSuccess(city)
+      Json.fromJson[City](json).asOpt must beSome(city)
     }
 
     "create correct formatter for case class with >= 2 fields" in {
@@ -27,7 +29,29 @@ class JsonFormatAnnotationTest extends Specification {
         "name" -> "Victor Hugo",
         "age" -> 46
       )
-      Json.fromJson[Person](json) === JsSuccess(person)
+      Json.fromJson[Person](json).asOpt must beSome(person)
+    }
+  }
+
+  "@jsonstrict annotation" should {
+
+    "create correct formatter for case class with 1 field" in {
+
+      val city = City2("San Francisco")
+      val json = Json.toJson(city)
+      json === Json.obj("name" -> "San Francisco")
+      Json.fromJson[City2](json).asOpt must beSome(city)
+    }
+
+    "create correct formatter for case class with >= 2 fields" in {
+
+      val person = Person2("Victor Hugo", 46)
+      val json = Json.toJson(person)
+      json === Json.obj(
+        "name" -> "Victor Hugo",
+        "age" -> 46
+      )
+      Json.fromJson[Person2](json).asOpt must beSome(person)
     }
   }
 }