Crate interface 

Typed, lossy-aware interface translation between API versions.

This crate models the migration of data structures between versioned API schemas. Each translation carries a Diff and is parameterised by a Lossiness marker that distinguishes whether the conversion is information-preserving (Lossless) or destructive (Lossy).

Quick start

use interface::{Diff, Lossless, Lossy, Translation, Upgrade, Downgrade};

#[derive(Debug, PartialEq, Eq)]
struct UserV1 { name: String }

#[derive(Debug, PartialEq, Eq)]
struct UserV2 { name: String, email: String }

impl Upgrade<UserV2> for UserV1 {
    type Lossiness = Lossless;
    fn upgrade(self) -> Translation<Self, UserV2, Lossless> {
        let diff = Diff::new().add("email", "default@example.com");
        Translation::new(self, Box::new(|s| UserV2 {
            name: s.name,
            email: "default@example.com".into(),
        }), diff)
    }
}

impl Downgrade<UserV1> for UserV2 {
    type Lossiness = Lossy;
    fn downgrade(self) -> Translation<Self, UserV1, Lossy> {
        let diff = Diff::new().sub("email", &self.email);
        Translation::new(self, Box::new(|s| UserV1 { name: s.name }), diff)
    }
}

let t = UserV1 { name: "Alice".into() }.upgrade();
assert!(!t.is_lossy());
let v2 = t.translate();
assert_eq!(v2.email, "default@example.com");

let t = v2.downgrade();
assert!(t.is_lossy());
let v1 = t.translate_lossy();
assert_eq!(v1.name, "Alice");

Structs

Diff

A human-readable record of fields added or removed during a translation.

Lossless

Marker: the translation preserves all information from the source.

Lossy

Marker: the translation drops information present in the source.

Translation

A pending translation from Source to Target.

Traits

Downgrade

Implement this to describe how Self migrates backward to Prev.

Lossiness

Sealed marker trait for translation lossiness.

Upgrade

Implement this to describe how Self migrates forward to Next.