equivalent of `#[serde(default)]` about borsh-rs HOT 2 CLOSED

@cameron1024 probably, you could achieve optionality by expressing it with type:

struct FooV3 {
  data: Vec<u8>,
  something_else: Option<i32>,
}

This juggling of encoded bytes of one type and decoding them as another type looks weird at first glance.
I've checked #serde[(default=... doc , it's not obvious how alleged #[borsh(default= ... attribute must behave, given that borsh format doesn't encode field names and current field being decoded is assumed from context (position in stream). Thus atm it's either a field is always present in output, or always skipped. As already mentioned, optionality can be expressed with Option<T> without using any additional encoding attributes.

from borsh-rs.

As already mentioned, optionality can be expressed with Option without using any additional encoding attributes.

@dj8yfo Well, None still requires an explicit 0 byte in the input, so FooV1 { data } is not byte-equal to FooV2 { data, something_else: None }.

@cameron1024 Since Borsh does not have schema inside, it can become ambiguous if you randomly try to have default field value and expect to skip it. I recommend you manually implement BorshDeserialize for FooV2 that will handle it manually.

from borsh-rs.