Branded

Branded types for Rust.

This crate is a continuation of the now-archived bty crate. It has been rewritten to be a derive macro, and to support SQLx 0.8.

Branded types are types that have a unique brand attached to them. They are particularly useful for managing ID types in large domains where it is easy to confuse the IDs of different domain objects. With Rust's nominal typing, branded types makes it impossible to confuse the IDs.

Thanks to Rust's trait system, we can transparently derive traits for our branded types based on the inner type, making them completely transparent to other libraries such as serde, and sqlx. This means that the brand types derive common traits such as Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Default, and Hash, if the inner type implements them.

The crate provides the Branded trait and the Branded derive macro.

The crate has no official MSRV, but it is tested against 1.82 and nightly.

# Cargo.toml

# The `serde` feature transparently derives the `Serialize` and `Deserialize` traits for the branded type.
# The `sqlx` feature derives the `Type`, `Encode`, and `Decode` traits for the branded type.
# The `uuid` feature exposes `nil()` and `new_v4()` methods on the branded type.
[dependencies]
branded = { version = "0.1", features = ["serde", "sqlx", "uuid"] }

Example

use branded::Branded;

// It is now impossible to confuse a UserId with a LogRecordId.
#[derive(Branded)]
pub struct UserId(String);

fn foo() {
    let user = UserId::new("123456".to_owned());
    // Get a reference to the inner type
    let user_id = user.inner();
    // Convert the branded type to the inner type
    let user_id = user.into_inner();
}

Serde

The serde feature transparently derives the Serialize and Deserialize traits for the branded type. Pass serde as an option to the Branded derive macro to enable this feature.

use branded::Branded;

#[derive(Branded)]
#[branded(serde)]
pub struct UserId(String);

SQLx

The sqlx feature derives the Type, Encode, and Decode traits for the branded type. Pass sqlx as an option to theBranded derive macro to enable this feature.

use branded::Branded;

#[derive(Branded)]
#[branded(sqlx)]
pub struct LogRecordId(i64);

UUID

The uuid feature exposes nil() and new_v4() methods on the branded type. Pass uuid as an option to the Branded derive macro to enable this feature.

use branded::Branded;

#[derive(Branded)]
#[branded(uuid)]
pub struct AuditLogEntryId(uuid::Uuid);

License

Licensed under the MIT License.