Serde support

[calebmer]

This PR adds support for optional serialization/deserialization using the serde library.

Pretty much a clone of @dtolnay's PR, contain-rs/linked-hash-map#48, which was reviewed by @apasel422.

[FlashCat]

r? @cgaebel

(I've picked a reviewer for you, use r? to override)

[dtolnay]

Link to a specific commit instead because the line numbers in "master" will become outdated.

• https://github.com/serde-rs/serde/blob/97856462467db2e90cf368e407c7ebcc726a01a9/serde/src/ser/impls.rs#L601-L611
• https://github.com/serde-rs/serde/blob/97856462467db2e90cf368e407c7ebcc726a01a9/serde/src/de/impls.rs#L694-L746

[calebmer]

Of course, thanks. Usually I'm good at catching that 😊

[dtolnay]

This does not need to be pub - then you don't need the #[allow(missing_docs)]. Same for LinearMapVisitor::new.

[calebmer]

I use LinearMap in a Value-like enum in my code base. I'd like to serialize/deserialize that value. Is there a good way to deserialize a map of its visitor is not public?

[dtolnay]

Even so, why does the visitor need to be public? All you should need are the Serialize and Deserialize traits implemented for LinearMap. Here is a working example that deserializes a Value-like enum containing a LinearMap:

#![feature(plugin, custom_derive)]
#![plugin(serde_macros)]

extern crate serde;
extern crate serde_yaml;
extern crate linear_map;

use linear_map::LinearMap;

#[derive(Deserialize, PartialEq, Debug)]
enum Value {
    Null,
    Map(LinearMap<String, String>),
}

fn main() {
    let y = "Map: {k: v}";
    let v: Value = serde_yaml::from_str(&y).unwrap();
    assert_eq!(v, expected());
}

fn expected() -> Value {
    let mut map = LinearMap::new();
    map.insert(String::from("k"), String::from("v"));
    Value::Map(map)
}

[calebmer]

I have a requirement to be on stable, so no custom derives, and we really don't want to use syntex because the interface is very undesirable 😐

serde_json uses the visitor implementation here, so as that was my reference I also did it that way. I thought it that was the canonical way of deserializing in this way.

It's not too hard for me to reimplement this functionality, I'll make it private 👍

[dtolnay]

Okay I understand now why it makes sense for it to be public. You can change it back.

[dtolnay]

r? @apasel422

[calebmer]

Ok, added the pub exports back in. @apasel422 look good?

[calebmer]

Fixed the build errors, @apasel422 how does contain-rs feel about this?

[calebmer]

Thanks so much for the merge! Is there a plan on when this will be released to http://crates.io?