Deserialize a type using FromStr

[dtolnay]

From IRC:

Is there a way to tell serde to desrialize my struct using it's FromStr implementation?

[dtolnay]

extern crate serde;

use std::str::FromStr;
use serde::{de, Deserialize, Deserializer};

struct S;

impl FromStr for S {
    type Err = String;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        unimplemented!()
    }
}

impl<'de> Deserialize<'de> for S {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
        where D: Deserializer<'de>
    {
        let s = String::deserialize(deserializer)?;
        FromStr::from_str(&s).map_err(de::Error::custom)
    }
}

[clarfonthey]

Considering how this is such a common pattern, is there not a way to do this with attributes?

[njam]

This is available in serde_with as display_fromstr.

[blueforesticarus]

The serde-with method works for fields of a struct, but if you want to serialize/deserialize the whole struct as a string via Display and FromStr, there does not seem to be any easy way to do that.

[adwhit]

@blueforesticarus sure it works, see: https://docs.rs/serde_with/latest/serde_with/derive.DeserializeFromStr.html