xstate-macros

Procedural macros for xstate-core:

• #[derive(TypedEvent)]: an enum as the typed event vocabulary of a machine (rename rules, payload mapping, From / TryFrom<Event>, declared_events(), check against a Machine);
• #[derive(TypedState)]: an enum naming a machine’s leaf states (is_active, check);
• statechart!: a Rust-literal chart DSL covering every XState construct, validated at compile time (duplicates, initial children, target resolution, tree shape) and building a Machine.

Status: 0.1.0, with trybuild UI tests for the diagnostics. The xstate-statemachine facade (feature macros) is enough: the generated code resolves xstate_core and serde_json through it, and a CI job checks a crate that depends on the facade alone (tests/facade-only/). Using xstate-macros directly still needs xstate-core (and serde for payload types) in the calling crate, and statechart! additionally needs serde_json.

#![allow(unused)]
fn main() {
use xstate_core::{MachineLogic, SyncInterpreter};
use xstate_macros::{TypedEvent, TypedState, statechart};

#[derive(TypedEvent)]
#[event(rename_all = "SCREAMING_SNAKE_CASE")]
enum DoorEvent { Open, Close }

#[derive(Debug, Clone, Copy, PartialEq, TypedState)]
#[state(machine = "door")]
enum Door { Closed, Opened }

let machine = statechart! {
    id: "door",
    initial: closed,
    states: {
        closed { on { OPEN => opened } }
        opened { on { CLOSE => closed } }
    }
}?;
let mut door = SyncInterpreter::new(machine, MachineLogic::dynamic());
door.start()?;
door.send(DoorEvent::Open)?;
assert!(Door::Opened.is_active(&door));
Ok::<(), xstate_core::Error>(())
}

Features

None (a proc-macro crate).

Python counterpart

The Pythonic DSL (xstate_statemachine.pythonic): class-based StateMachine / State, the builder and the functional form. Rust gets typed enums and a compile-time-checked macro instead of metaclass scanning.