Set: unwrap nested *Json so Get can traverse them

simplejson.go

@@ -53,19 +53,37 @@ func (j *Json) MarshalJSON() ([]byte, error) {
 	return json.Marshal(&j.data)
 }
 
+// unwrapJSON stores the underlying payload when val is a Json wrapper.
+// Get() wraps map values in a new Json; leaving a *Json in the map would
+// make nested Get/Map fail because they type-assert to map[string]interface{}.
+func unwrapJSON(val interface{}) interface{} {
+	switch v := val.(type) {
+	case *Json:
+		if v == nil {
+			return nil
+		}
+		return v.data
+	case Json:
+		return v.data
+	default:
+		return val
+	}
+}
+
 // Set modifies `Json` map by `key` and `value`
 // Useful for changing single key/value in a `Json` object easily.
 func (j *Json) Set(key string, val interface{}) {
 	m, err := j.Map()
 	if err != nil {
 		return
 	}
-	m[key] = val
+	m[key] = unwrapJSON(val)
 }
 
 // SetPath modifies `Json`, recursively checking/creating map keys for the supplied path,
 // and then finally writing in the value
 func (j *Json) SetPath(branch []string, val interface{}) {
+	val = unwrapJSON(val)
 	if len(branch) == 0 {
 		j.data = val
 		return

simplejson_test.go

@@ -221,6 +221,48 @@ func TestSet(t *testing.T) {
 	}
 }
 
+func TestSetJsonValue(t *testing.T) {
+	xx, err := NewJson([]byte(`{"name": "Alice"}`))
+	if err != nil {
+		t.Fatalf("err %#v", err)
+	}
+
+	yy := New()
+	yy.Set("Contact", xx)
+	s, err := yy.Get("Contact").Get("name").String()
+	if err != nil {
+		t.Fatalf("err %#v", err)
+	}
+	if s != "Alice" {
+		t.Errorf("got %#v", s)
+	}
+
+	yy2 := New()
+	yy2.Set("Contact", xx.Interface())
+	s, err = yy2.Get("Contact").Get("name").String()
+	if err != nil {
+		t.Fatalf("err %#v", err)
+	}
+	if s != "Alice" {
+		t.Errorf("got %#v", s)
+	}
+
+	yy.SetPath([]string{"nested", "contact"}, xx)
+	s, err = yy.GetPath("nested", "contact", "name").String()
+	if err != nil {
+		t.Fatalf("err %#v", err)
+	}
+	if s != "Alice" {
+		t.Errorf("got %#v", s)
+	}
+
+	var n *Json
+	yy.Set("empty", n)
+	if yy.Get("empty").Interface() != nil {
+		t.Errorf("nil *Json should store nil, got %#v", yy.Get("empty").Interface())
+	}
+}
+
 func TestReplace(t *testing.T) {
 	js, err := NewJson([]byte(`{}`))
 	if err != nil {