Jsonutils: pass opt for object in object (#16615)

* jsonutils: fromJson forward opt param fix

* jsonutils: object in object test + fix: opt pass

lib/std/jsonutils.nim

@@ -119,7 +119,7 @@ template fromJsonFields(newObj, oldObj, json, discKeys, opt) =
     when key notin discKeys:
       if json.hasKey key:
         numMatched.inc
-        fromJson(val, json[key])
+        fromJson(val, json[key], opt)
       elif opt.allowMissingKeys:
         # if there are no discriminant keys the `oldObj` must always have the
         # same keys as the new one. Otherwise we must check, because they could

tests/stdlib/tjsonutils.nim

@@ -123,6 +123,9 @@ template fn() =
       a: int
       b: string
       c: float
+    type Bar = object
+      foo: Foo
+      boo: string
     var f: seq[Foo]
     try:
       fromJson(f, parseJson """[{"b": "bbb"}]""")
@@ -131,6 +134,9 @@ template fn() =
       doAssert true
     fromJson(f, parseJson """[{"b": "bbb"}]""", Joptions(allowExtraKeys: true, allowMissingKeys: true))
     doAssert f == @[Foo(a: 0, b: "bbb", c: 0.0)]
+    var b: Bar
+    fromJson(b, parseJson """{"foo": {"b": "bbb"}}""", Joptions(allowExtraKeys: true, allowMissingKeys: true))
+    doAssert b == Bar(foo: Foo(a: 0, b: "bbb", c: 0.0))
 
   block testHashSet:
     testRoundtrip(HashSet[string]()): "[]"