fix #3884. restore json serialization of Crystal::Exception

Brian J. Cardiff · Brian J. Cardiff · commit 82671f506f25 · 2017-01-13T11:03:01.000-03:00
diff --git a/src/compiler/crystal/tools/playground/server.cr b/src/compiler/crystal/tools/playground/server.cr
@@ -121,7 +121,9 @@ module Crystal::Playground
       json.object do
         json.field "message", ex.to_s
         if ex.is_a?(Crystal::Exception)
-          json.field "payload", ex.to_s
+          json.field "payload" do
+            ex.to_json(json)
+          end
         end
       end
     end
