Deserialize true/false from 1/0

[dtolnay]

Question from IRC:

<Tachyon_> if I have a json where I have a field where true/false is represented as 0/1, can I make serde_json to automagically map it to a bool ?

[dtolnay]

#[macro_use]
extern crate serde_derive;

extern crate serde;
extern crate serde_json;

use serde::de::{self, Deserialize, Deserializer, Unexpected};

#[derive(Deserialize, Debug)]
struct Tachyon {
    #[serde(deserialize_with = "bool_from_int")]
    value: bool,
}

fn bool_from_int<'de, D>(deserializer: D) -> Result<bool, D::Error>
where
    D: Deserializer<'de>,
{
    match u8::deserialize(deserializer)? {
        0 => Ok(false),
        1 => Ok(true),
        other => Err(de::Error::invalid_value(
            Unexpected::Unsigned(other as u64),
            &"zero or one",
        )),
    }
}

fn main() {
    println!("{:?}", serde_json::from_str::<Tachyon>("{\"value\":0}").unwrap());
    println!("{:?}", serde_json::from_str::<Tachyon>("{\"value\":1}").unwrap());
    println!("{}", serde_json::from_str::<Tachyon>("{\"value\":2}").unwrap_err());
}

Tachyon { value: false }
Tachyon { value: true }
invalid value: integer `2`, expected zero or one at line 1 column 11

[0xpr03]

Thanks for that example.
In case anyone was wondering how to do the same with strings (with the CSV crate in my case) here my code:

/// example struct
#[derive(Debug,Deserialize)]
struct MyStruct {
    #[serde(deserialize_with = "bool_from_string")]
    is_ok: bool
}

/// Deserialize bool from String with custom value mapping
fn bool_from_string<'de, D>(deserializer: D) -> Result<bool, D::Error>
where
    D: Deserializer<'de>,
{
    match String::deserialize(deserializer)?.as_ref() {
        "OK" => Ok(true),
        "nOK" => Ok(false),
        other => Err(de::Error::invalid_value(
            Unexpected::Str(other),
            &"OK or nOK",
        )),
    }
}