Crate serde_ignored

Find out about keys that are ignored when deserializing data. This crate provides a wrapper that works with any existing Serde Deserializer and invokes a callback on every ignored field.

You can use this to warn users about extraneous keys in a config file, for example.

Note that if you want unrecognized fields to be an error, consider using the #[serde(deny_unknown_fields)] attribute instead.

Example

use serde::Deserialize;
use std::collections::{BTreeSet as Set, BTreeMap as Map};

#[derive(Debug, PartialEq, Deserialize)]
struct Package {
    name: String,
    dependencies: Map<String, Dependency>,
}

#[derive(Debug, PartialEq, Deserialize)]
struct Dependency {
    version: String,
}

let j = r#"{
    "name": "demo",
    "dependencies": {
        "serde": {
            "version": "1.0",
            "typo1": ""
        }
    },
    "typo2": {
        "inner": ""
    },
    "typo3": {}
}"#;

// Some Deserializer.
let jd = &mut serde_json::Deserializer::from_str(j);

// We will build a set of paths to the unused elements.
let mut unused = Set::new();

let p: Package = serde_ignored::deserialize(jd, |path| {
    unused.insert(path.to_string());
})?;

assert_eq!(p, Package {
    name: "demo".to_owned(),
    dependencies: {
        let mut map = Map::new();
        map.insert("serde".to_owned(), Dependency {
            version: "1.0".to_owned(),
        });
        map
    },
});

assert_eq!(unused, {
    let mut expected = Set::new();
    expected.insert("dependencies.serde.typo1".to_owned());
    expected.insert("typo2".to_owned());
    expected.insert("typo3".to_owned());
    expected
});

Structs

Deserializer

Deserializer adapter that invokes a callback with the path to every unused field of the input.

Enums

Path	Path to the current value in the input, like dependencies.serde.typo1.

Functions

deserialize

Entry point. See crate documentation for an example.