type (
	ComplexObject struct {
		Field1 string
		Field2 []ComplexSubObject
	}
	ComplexSubObject struct {
		SubField1 string
		SubField2 struct {
			SubSubField1 string
			SubSubField2 string
		}
	}

	SimpleObject struct {
		Field1 string
		Field2 []SimpleSubObject
	}
	SimpleSubObject struct {
		SubField1 string
		SubField2 struct {
			SubSubField1 string
		}
	}
)

func TestFieldMismatchLoading() {
	ctx := context.Background()
	c, err := datastore.NewClient(ctx, "my-project")
	if err != nil {
		panic(err)
	}

	o := ComplexObject{
		Field1: "field-1",
		Field2: []ComplexSubObject{{
			SubField1: "sub-field-1",
			SubField2: struct {
				SubSubField1 string
				SubSubField2 string
			}{
				SubSubField1: "sub-sub-field-1",
				SubSubField2: "sub-sub-field-2",
			},
		}},
	}
	fmt.Printf("%+v\n", o)
	key, err := c.Put(ctx, datastore.IncompleteKey("test", nil), &o)
	if err != nil {
		panic(err)
	}

	var s SimpleObject
	err = c.Get(ctx, key, &s)
	if err != nil {
		if _, ok := err.(*datastore.ErrFieldMismatch); !ok {
			panic(err)
		}
	}
	fmt.Printf("%+v\n", s)
}