serde_describe 0.2.2

Make a non-self-describing serde format (like bincode, bitcode or postcard) behave as like a self-describing one by transparently serializing a schema alongside (or separately from) the data.

The main entry point to the crate is [SelfDescribed]. For advanced uses [SchemaBuilder] and [Schema] may also be of interest.

use serde::{Deserialize, Serialize};
use serde_describe::{Schema, SelfDescribed};

// Define a type that non-self-describing formats would generally struggle
// with, using skipped fields and untagged unions.
#[derive(Debug, PartialEq, Serialize, Deserialize)]
struct TopLevel {
    int32: u32,

    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    items: Vec<Item>,
}

#[derive(Debug, PartialEq, Serialize, Deserialize)]
#[serde(untagged)]
enum Item {
    Int(u32),
    Str(String),
}

// Serialize a `Vec<TopLevel>` using the `SelfDescribed` wrapper and bitcode, a
// particularly restrictive binary format.
let original = vec![
    TopLevel {
        int32: 10,
        items: vec![Item::Str("hello".to_owned()), Item::Int(10)],
    },
    TopLevel {
        int32: 20,
        items: Vec::new(),
    },
];
let bytes = bitcode::serialize(&SelfDescribed(&original))?;

// Then deserialize using the same wrapper to use the embedded schema.
let roundtripped =
    bitcode::deserialize::<SelfDescribed<Vec<TopLevel>>>(&bytes)?;
assert_eq!(roundtripped, original);

# Ok::<_, Box<dyn std::error::Error>>(())