Fix deserialization of objects with default field values

Author: Anuken

src/jsony.nim

@@ -599,6 +599,7 @@ proc fromJson*[T](s: string, x: typedesc[T]): T =
   ## * Missing json fields keep their default values.
   ## * `proc newHook(foo: var ...)` Can be used to populate default values.
   var i = 0
+  result = default(T)
   s.parseHook(i, result)
   eatSpace(s, i)
   if i != s.len:

tests/test_objects.nim

@@ -7,6 +7,15 @@ block:
   var v = s.fromJson(Entry1)
   doAssert v.color == ""
 
+block:
+  type Frog = object
+    legs: int = 4
+
+  var s = "{}"
+  var f = s.fromJson(Frog)
+  # Make sure the default value is deserialized correctly.
+  doAssert f.legs == 4
+
 block:
   type Foo2 = ref object
     field: string