Expose fieldName when able in deserialization errors

3 files changed, 19 insertions, 5 deletions

diff --git a/src/main/scala/spray/json/ProductFormats.scala b/src/main/scala/spray/json/ProductFormats.scala
index 9914b55..9e494ff 100644
--- a/src/main/scala/spray/json/ProductFormats.scala
+++ b/src/main/scala/spray/json/ProductFormats.scala
@@ -56,9 +56,11 @@ trait ProductFormats extends ProductFormatsInstances {
       try reader.read(x.fields(fieldName))
       catch {
         case e: NoSuchElementException =>
-          deserializationError("Object is missing required member '" + fieldName + "'", e)
+          deserializationError("Object is missing required member '" + fieldName + "'", e, fieldName :: Nil)
+        case DeserializationException(msg, cause, fieldNames) =>
+          deserializationError(msg, cause, fieldName :: fieldNames)
       }
-    case _ => deserializationError("Object expected in field '" + fieldName + "'")
+    case _ => deserializationError("Object expected in field '" + fieldName + "'", fieldNames = fieldName :: Nil)
   }
 
   protected def extractFieldNames(classManifest: ClassManifest[_]): Array[String] = {
diff --git a/src/main/scala/spray/json/package.scala b/src/main/scala/spray/json/package.scala
index fe37c8b..f79b99e 100644
--- a/src/main/scala/spray/json/package.scala
+++ b/src/main/scala/spray/json/package.scala
@@ -20,7 +20,7 @@ package object json {
 
   type JsField = (String, JsValue)
 
-  def deserializationError(msg: String, cause: Throwable = null) = throw new DeserializationException(msg, cause)
+  def deserializationError(msg: String, cause: Throwable = null, fieldNames: List[String] = Nil) = throw new DeserializationException(msg, cause, fieldNames)
   def serializationError(msg: String) = throw new SerializationException(msg)
 
   def jsonReader[T](implicit reader: JsonReader[T]) = reader
@@ -32,7 +32,7 @@ package object json {
 
 package json {
 
-  class DeserializationException(msg: String, cause: Throwable = null) extends RuntimeException(msg, cause)
+  case class DeserializationException(msg: String, cause: Throwable = null, fieldNames: List[String] = Nil) extends RuntimeException(msg, cause)
   class SerializationException(msg: String) extends RuntimeException(msg)
 
   private[json] class PimpedAny[T](any: T) {
@@ -44,4 +44,4 @@ package json {
     def asJson: JsValue = parseJson
     def parseJson: JsValue = JsonParser(string)
   }
-}
\ No newline at end of file
+}
diff --git a/src/test/scala/spray/json/ProductFormatsSpec.scala b/src/test/scala/spray/json/ProductFormatsSpec.scala
index a290604..ba9d907 100644
--- a/src/test/scala/spray/json/ProductFormatsSpec.scala
+++ b/src/test/scala/spray/json/ProductFormatsSpec.scala
@@ -23,6 +23,7 @@ class ProductFormatsSpec extends Specification {
   case class Test0()
   case class Test2(a: Int, b: Option[Double])
   case class Test3[A, B](as: List[A], bs: List[B])
+  case class Test4(t2: Test2)
   case class TestTransient(a: Int, b: Option[Double]) {
     @transient var c = false
   }
@@ -35,6 +36,7 @@ class ProductFormatsSpec extends Specification {
     implicit val test0Format = jsonFormat0(Test0)
     implicit val test2Format = jsonFormat2(Test2)
     implicit def test3Format[A: JsonFormat, B: JsonFormat] = jsonFormat2(Test3.apply[A, B])
+    implicit def test4Format = jsonFormat1(Test4)
     implicit def testTransientFormat = jsonFormat2(TestTransient)
     implicit def testStaticFormat = jsonFormat2(TestStatic)
     implicit def testMangledFormat = jsonFormat1(TestMangled)
@@ -71,6 +73,16 @@ class ProductFormatsSpec extends Specification {
     "throw a DeserializationException if the JsValue is not a JsObject" in (
       JsNull.convertTo[Test2] must throwA(new DeserializationException("Object expected in field 'a'"))
     )
+    "expose the fieldName in the DeserializationException when able" in {
+      JsNull.convertTo[Test2] must throwA[DeserializationException].like {
+        case DeserializationException(_, _, fieldNames) => fieldNames mustEqual "a" :: Nil
+      }
+    }
+    "expose all gathered fieldNames in the DeserializationException" in {
+      JsObject("t2" -> JsObject("a" -> JsString("foo"))).convertTo[Test4] must throwA[DeserializationException].like {
+        case DeserializationException(_, _, fieldNames) => fieldNames mustEqual "t2" :: "a" :: Nil
+      }
+    }
   }
 
   "A JsonProtocol mixing in NullOptions" should {