mnesis-macros

Procedural macros for mnesis. Three macros, zero boilerplate.

#[derive(DomainEvent)]

Derive on an enum. Generates Message + DomainEvent impls with name() returning variant names as &'static str.

#[derive(Debug, Clone, DomainEvent)]
enum AccountEvent {
    Opened(AccountOpened),
    Deposited(MoneyDeposited),
    Closed(AccountClosed),
}

#[mnesis::aggregate]

Attribute macro on a unit struct. Generates impl Aggregate plus a convenience BankAccount::new(id) -> AggregateRoot<Self> constructor; the struct stays a bare marker. Implement Handle<C> on the marker as handle(state, cmd) -> events.

#[mnesis::aggregate(state = AccountState, error = AccountError, id = AccountId)]
struct BankAccount;

impl Handle<Withdraw> for BankAccount {
    fn handle(
        state: &AccountState,
        cmd: Withdraw,
    ) -> Result<Option<Events<AccountEvent>>, AccountError> {
        // pure decision: read state, return decided events — or `Ok(None)`
        // when the command changes nothing
    }
}

#[mnesis::transforms]

Attribute macro on an impl block. Generates an Upcaster impl for schema evolution. Transform functions are annotated with #[transform(event = "...", from = N, to = N+1)].

#[mnesis::transforms(aggregate = BankAccount, error = MyUpcastError)]
impl BankAccountTransforms {
    #[transform(event = "Deposited", from = 1, to = 2)]
    fn add_currency(payload: &[u8]) -> Result<Vec<u8>, MyUpcastError> {
        // migrate v1 → v2
    }
}

MSRV & stability

MSRV 1.95 (pinned stable). 1.0 tier, version-locked to mnesis with an exact = pin. See STABILITY.md.

License

Licensed under your choice of MIT or Apache-2.0.