Simpler way to write serde custom deserialization?

[anon80458984]

I'm finding serde custom deserialization impls to be alot more error prone than I expect.

I'm wondering if there is a library that lets me do the following:

1. Suppose we want to custom derive on type T

2. I want to specify types U along with two functions

f :: T -> Result<U, String>
g :: U -> Result<T, String>

3. U is serialized via standard derive macro.

4. If serde comes across T during serialization, it calls f and uses that output.

5. If serde comes across T during deserialization, it gets a U from the data, then calls g.

Is there a library that does this? The main here is that I'd rather write f and g rather than write all the visitor patterns.

[Hyeonu]

You can do so within the body of Serialize::serialize and Deserialize::deserialize impl.

impl Serialize for T {
    fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
        f(self).map_err(S::Error::custom)?.serialize(s)
    }
}