I’m happy to announce that I’ve released serde 0.3 on crates.io today. For those unfamiliar with serde, it’s a generic serialization framework, much like rustc-serialize, but much more powerful. Check out my serialization series if you’re interested in serde’s original development.

There’s been a ton of work since 0.2. Here are the highlights:

• Ported over from std::old_io to std::io. There is a bit of a performance hit when serializing to &mut [u8], although it’s really not that bad. In my goser benchmarks, previously it ran in 373 MB/s, but now it’s running at 260 MB/s. However, this hasn’t impacted the Vec<u8> serialization performance, nor deserialization performance.

• Much better JSON deserialization errors. Now std::io::Error is properly propogated, and error locations are reported when a Deserialize raises an error.

• Merged serde::ser::Serializer and serde::ser::Visitor.

• Renamed serde::ser::Serialize::visit to serde::ser::Serialize::serialize.

• Replaced serde::ser::{Seq,Map}Visitor::size_hint with a len() method that returns an optional length. This has a little stronger emphasis that we either need an exactly length or no length. Formats that need an exact length should make sure to verify the length passed in matches the actual amount of values serialized.

• serde::json now deserializes missing values as a ().

• Finished implementing #[derive(Serialize, Deserialize)] for all struct and enum forms.

• Ported serde_macros over to aster and quasi, which simplies code generation.

• Removed the unnessary first argument from visit_{seq,map}_elt.

• Rewrote enum deserializations to not require allocations. Oddly enough this is a tad slower than the allocation form. I suspect it’s coming from the function calls not getting inlined away.

• Allowed enum serialization and deserialization to support more than one variant.

• Allowed Deserialize types to hint that it’s expecting a sequence or a map.

• Allowed maps to be deserialized from a ().

• Added a serde::bytes::{Bytes,ByteBuf}, which wrap &[u8]/Vec<u8> to allow some formats to encode these values more efficiently than generic sequences.

• Added serde::de::value, which contains some helper deserializers to deserialize from a Rust type.

• Added impls for most collection types in the standard library.

Thanks everyone that’s helped out with this release!