Added method for sorted print

This method prints in the same format
as PrettyPrinter but sorts the keys
of each object lexicographically.

The impetus for this change was this
question:
http://stackoverflow.com/questions/31418626/sort-fields-in-rendered-json

In general it is useful to be able to have more deterministic
control over the ordering of output, if diff tools
are to be used.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/main/scala/spray/json/PrettyPrinter.scala b/src/main/scala/spray/json/PrettyPrinter.scala
index 57cf35e..6af5443 100644
--- a/src/main/scala/spray/json/PrettyPrinter.scala
+++ b/src/main/scala/spray/json/PrettyPrinter.scala
@@ -37,9 +37,11 @@ trait PrettyPrinter extends JsonPrinter {
     }
   }
 
+  protected def organiseMembers(members: Map[String, JsValue]): Seq[(String, JsValue)] = members.toSeq
+
   protected def printObject(members: Map[String, JsValue], sb: StringBuilder, indent: Int) {
     sb.append("{\n")    
-    printSeq(members, sb.append(",\n")) { m =>
+    printSeq(organiseMembers(members), sb.append(",\n")) { m =>
       printIndent(sb, indent + Indent)
       printString(m._1, sb)
       sb.append(": ")