UnmarshalFromString can't Unmarshal empty string.

[yankooo]

for example:

func Test_customize_field_by_extension(t *testing.T) {
	should := require.New(t)
	cfg := jsoniter.Config{}.Froze()
	cfg.RegisterExtension(&testExtension{})
	obj := TestObject1{}
	err := cfg.UnmarshalFromString(``, &obj)
	should.Nil(err)
}

expect: err is nil, but err: "Read: unexpected value type: 0, error found in #0 byte of ...||..., bigger context ...||..."。

can't understand this error is a valid case?

[fraenky8]

An empty string is not valid json. The stdlib throws an error as well: unexpected end of JSON input.

can't understand this error is a valid case?

To answer your question, yes this error is valid.