feat req: skip some fields in the struct

[fslongjin]

In serde, we can use #[serde(skip)] on fields we don't want to serialize/deserialize.
Here is an example:

#[derive(Serialize, Deserialize)]
struct A {
  xxxx: B,
  #[serde(skip)]
  yyyy: C,
}

In the case above, Type C should not derive Serialize and Deserialize.

[lbirkert]

This would be a great addition, as sometimes certain fields can be computed from others so storing every field is wasteful (if computing performance is not a factor here). How does it work in practice though? Do I have to provide a value for yyyy while deserializing or does it use the default value? How does serde currently handle it?

[lbirkert]

The semantic way to do this currently would be just to create a seperate struct.

struct A {
  xxxx: B,
  yyyy: C,
}

#[derive(Encode, Decode)]
struct ARaw {
  xxxx: B,
}

impl From<A> for ARaw {
     fn from(val: A) -> Self {
        ARaw { xxxx: val.xxxx }
    }
}

What benefits does creating a separate macro bring except boilerplate reduction? What if I don't want my yyyy to implement default? How would we handle this case?

[finnbear]

#[serde(skip)] uses Default::default() (can be overridden by #[serde(skip, default = "some_fn")])

[lbirkert]

seams reasonable then