allow nullable in marshalled classes, for people who like to shoot themselves in the foot

Author: mpollmeier

gremlin-scala/src/test/scala/gremlin/scala/marshallable/MarshallableSpec.scala

@@ -6,6 +6,7 @@ import gremlin.scala.{
   asScalaVertex,
   id,
   label,
+  nullable,
   underlying,
   Edge,
   Element,
@@ -26,6 +27,7 @@ case class CCWithOption(i: Int, s: Option[String])
 case class CCWithOptionValueClass(s: String, i: Option[MyValueClass])
 case class CCWithOptionAnyVal(x: Option[Int], y: Option[Long])
 case class CCWithList(s: String, ss: List[String], is: List[Int], ds: List[Double])
+case class CCWithNullable(i: Int, @nullable maybeNull: String)
 
 case class CCWithOptionId(s: String, @id id: Option[Int])
 case class CCWithOptionIdNested(s: String, @id id: Option[Int], i: MyValueClass)
@@ -151,6 +153,13 @@ class MarshallableSpec extends WordSpec with Matchers {
       properties.map(_.value) shouldBe List("one", "two")
     }
 
+    "allows members to be `null` if annotated with `@nullable`" in new Fixture {
+      val cc = CCWithNullable(i = 42, maybeNull = null)
+
+      val v = graph + cc
+      v.toCC[CCWithNullable] shouldBe cc
+    }
+
     "define their custom marshaller" in new Fixture {
       val ccWithOptionNone = CCWithOption(Int.MaxValue, None)
 

macros/src/main/scala/gremlin/scala/Annotations.scala

@@ -14,6 +14,12 @@ class underlying extends StaticAnnotation
 @getter @beanGetter
 class id extends StaticAnnotation
 
+/** annotate a non-option member with `@nullable` to allow `null` values.
+  * by default this would throw an error on deserialization
+  * a.k.a. license to shoot yourself in the foot */
+@getter @beanGetter
+class nullable extends StaticAnnotation
+
 class label(val label: String = "") extends StaticAnnotation
 
 object Annotations {

macros/src/main/scala/gremlin/scala/Marshallable.scala

@@ -32,7 +32,7 @@ object Marshallable {
           val decoded = name.decodedName.toString
           val returnType = field.returnType
 
-          def handleStandardProperty = {
+          def handleStandardProperty(nullable: Boolean) = {
             // check if the property is a value class and try to extract everything we need to unwrap it
             val treesForValueClass = for {
               valueName <- valueGetter(returnType)
@@ -45,9 +45,16 @@ object Marshallable {
                _toCCParams :+ q"$valueClassCompanion(element.value[$wrappedType]($decoded)).asInstanceOf[$returnType]")
             }
             treesForValueClass.getOrElse { //normal property
+              val toCCParams =
+                if (!nullable) {
+                  q"element.value[$returnType]($decoded)"
+                } else {
+                  // for people who like to shoot themselves in the foot
+                  q"new _root_.gremlin.scala.PropertyOps(element.property[$returnType]($decoded)).toOption.orNull"
+                }
               (_idParam,
                _fromCCParams :+ q"_root_.scala.collection.immutable.List($decoded -> cc.$name)",
-               _toCCParams :+ q"element.value[$returnType]($decoded)")
+               _toCCParams :+ toCCParams)
             }
           }
 
@@ -171,7 +178,8 @@ object Marshallable {
             } else if (returnType.typeSymbol == weakTypeOf[List[_]].typeSymbol) {
               handleListProperty
             } else {
-              handleStandardProperty
+              handleStandardProperty(
+                nullable = field.annotations.map(_.tree.tpe).contains(weakTypeOf[nullable]))
             }
           }
 
@@ -204,9 +212,7 @@ object Marshallable {
           }
       """
     }
-    // if (tpe.toString.contains("CCWithList")) {
-    // println(ret)
-    // }
+    // if (tpe.toString.contains("CCWithNullable")) println(ret)
     ret
   }