Question about DER encoding discrepancy between versions (0.7 -> 0.8)

Hi! I had some tests for my project to make sure the serialization format is preserved across project updates. I was initially only testing deserialization but recently made a change in my project that made testing serialization deterministically possible as well. The interesting thing is that I noticed the serialization format changed from when I wrote the test (this was back on v0.7).

I wrote a quick test to check this out and came up with two results:

#[derive(Debug, Clone, AsnType, Encode, Decode)]
#[rasn(choice)]
enum Tx {
    #[rasn(tag(explicit(0)))]
    Test,
    #[rasn(tag(explicit(1)))]
    Reset {
        #[rasn(tag(explicit(0)))]
        keys: Option<Vec<u32>>,
    }
}
let tx1 = Tx::Reset { keys: None };
let tx1_ser = rasn::der::encode(&tx1).unwrap();
println!("--- {:?}", tx1_ser);

In v0.7 this produces (https://lapo.it/asn1js/#oQIwAA):

[161, 2, 48, 0]

And in v0.8 this produces (https://lapo.it/asn1js/#oQQwAqAA):

[161, 4, 48, 2, 160, 0]

I'm not entirely sure which one "correct" now. It seems v0.8+ encode None as their own sequence instead of omitting the value...is this the desired behavior? From my (admittedly limited) understanding, OPTIONAL fields are omitted when they are blank.

librasn / rasn

Question about DER encoding discrepancy between versions (0.7 -> 0.8) #217