Fix issue with lost siblings when modifying at some path (#3)

Author: svroonland

src/main/scala/nl/vroste/playjsonoptics/JsLens.scala

@@ -75,17 +75,16 @@ object JsLens {
   private def optionalValueAtPath(path: JsPath): Lens[JsValue, Option[JsValue]] =
     Lens[JsValue, Option[JsValue]](path.asSingleJsResult(_).asOpt) {
       newValueOpt =>
-        root =>
-          root match {
-            case rootObj@JsObject(_) =>
-              newValueOpt match {
-                case Some(obj) =>
-                  rootObj ++ JsPath.createObj((path, obj))
-                case None =>
-                  path.json.prune.reads(rootObj).getOrElse(rootObj)
-              }
-            case _ => root
-          }
+        {
+          case rootObj@JsObject(_) =>
+            newValueOpt match {
+              case Some(obj) =>
+                rootObj deepMerge JsPath.createObj((path, obj))
+              case None =>
+                path.json.prune.reads(rootObj).getOrElse(rootObj)
+            }
+          case root => root
+        }
     }
 
   // Allows remove syntax

src/test/scala/nl/vroste/playjsonoptics/JsLensSpec.scala

@@ -79,6 +79,32 @@ class JsLensSpec extends FlatSpec with MustMatchers with Inside with OptionValue
     optic.modify(_ + "X")(json) mustBe expectedJson
   }
 
+  it must "leave siblings intact when modifing at some path" in {
+    val json = Json.parse(
+      """
+        |{"a" : {
+        |   "b" : "someValue",
+        |   "c" : "otherValue"
+        |   }
+        | }
+      """.stripMargin
+    )
+
+    val expectedJson = Json.parse(
+      """
+        |{"a" : {
+        |   "b" : "someValue",
+        |   "c" : "otherValueadd"
+        |   }
+        | }
+      """.stripMargin
+    )
+
+    val optic = JsLens[String](__ \ "a" \ "c")
+
+    optic.modify(_ + "add")(json) mustBe expectedJson
+  }
+
   "Removing at a given path" must "prune the JSON at that path" in {
     val json: JsValue = Json.obj(
       "field1" -> Json.obj(