Migrate command emit to effects

Ignite Element now treats commands as intent triggers and effects as the place where state transitions produce DOM events.

Before

const registerToggle = igniteCore({
  source: machine,
  events: (event) => ({
    toggled: event<{ isOn: boolean }>(),
  }),
  commands: ({ actor, emit }) => ({
    toggle: () => {
      actor.send({ type: "TOGGLE" });
      emit("toggled", { isOn: true });
    },
  }),
});

After

const registerToggle = igniteCore({
  source: machine,
  events: (event) => ({
    toggled: event<{ isOn: boolean }>(),
  }),
  commands: ({ actor }) => ({
    toggle: () => {
      actor.send({ type: "TOGGLE" });
    },
  }),
  effects: ({ snapshot, prevSnapshot, emit }) => {
    if (snapshot.matches("on") === prevSnapshot.matches("on")) return;
    emit("toggled", { isOn: snapshot.matches("on") });
  },
});

Migration checklist

1. Remove emit from the commands parameter list.
2. Keep commands limited to actor/store/observable intent.
3. Add an effects callback and destructure only the fields you use.
4. Compare state before emitting, such as snapshot with prevSnapshot.
5. Keep your events map so emit stays typed.

Scripted assist

From the repo root:

node scripts/migrate-emit-to-effects.mjs

The script reports files that still:

• destructure emit in commands
• call emit(...) in code that likely needs migration

Use --report <path> to save the output to a file.

Breaking release note

emit has been removed from command context. Commands still receive { actor, command, host }; typed event emission belongs in effects().

Release boundary

• Migration tooling and docs remain available to help with old command emit patterns.
• effects() is now the supported path for typed event emission.