statelyai/xstate xstate@6.0.0-alpha.4

on GitHub

Major Changes

• c3f7a9d: Actor logic now returns effects from both regular and initial transitions.

  Hand-written actor logic should return [snapshot, effects] from transition(...) and provide initialTransition(...) for creating the initial [snapshot, effects] tuple. getInitialSnapshot(...) remains available for snapshot-only reads.

  const logic = {
    transition: (snapshot, event) => [snapshot, []],
    initialTransition: (input, _scope) => [
      {
        status: 'active',
        output: undefined,
        error: undefined,
        input
      },
      []
    ],
    getInitialSnapshot: (scope, input) =>
      logic.initialTransition(input, scope)[0]
  };

  transition(...) and initialTransition(...) continue to return [snapshot, actions] for machine logic.

  fromStore(...) effects now run after the actor snapshot is committed, so effect callbacks read the updated snapshot from enqueue.getSnapshot().

• 309b106: Add schemas.children for explicitly typing child actor refs by child ID. Declared child refs type children.someId, child snapshots, and invoke configs so invoke: { id: 'someId', src } must match the declared child actor contract.

• fa2bbf0: Built-in executable effects returned from transition(...) and initialTransition(...) are now easier to inspect declaratively.

  Use isBuiltInExecutableAction(effect) to narrow an executable effect to XState's built-in effect union, then switch on effect.type to access stable, named metadata fields:

  const [snapshot, effects] = initialTransition(machine);
  
  for (const effect of effects) {
    if (!isBuiltInExecutableAction(effect)) {
      continue;
    }
  
    switch (effect.type) {
      case '@xstate.start':
        effect.id;
        effect.logic;
        effect.src;
        effect.input;
        break;
  
      case '@xstate.sendTo':
        effect.target;
        effect.event;
        effect.delay;
        break;
  
      case '@xstate.raise':
        effect.event;
        effect.delay;
        break;
    }
  }

  The built-in stop effect is now exposed as @xstate.stop, matching @xstate.start.