system-id.md

Suggest using systemId for invoked or spawned actors

Provide systemId for invoked and spawned actors to make them available in the actor.system registry.

Rule Details

Specifying a systemId property within invoke blocks, and within options passed as the second argument to spawn calls, will make the actor available in the actor.system registry.

The systemId property is supported in XState version 5 and above.

Examples of incorrect code for this rule:

// ❌ missing systemId in an invoke block
createMachine({
  states: {
    playing: {
      invoke: {
        src: 'game',
      },
    },
  },
})

// ❌ missing systemId in a spawn call
createMachine({
  states: {
    initializing: {
      entry: assign({
        gameRef: () => spawn(game),
      }),
    },
  },
})

// ❌ invalid systemId value
createMachine({
  states: {
    playing: {
      invoke: {
        src: 'game',
        system: [],
      },
    },
  },
})

// ❌ duplicate systemIds
createMachine({
  states: {
    playing: {
      invoke: {
        src: 'game',
        systemId: 'actor1',
      },
      entry: assign({
        gameRef: () => spawn(game, { systemId: 'actor1' }),
      }),
    },
  },
})

Examples of correct code for this rule:

// ✅
createMachine{{
  states: {
    playing: {
      invoke: {
        src: 'game',
        systemId: 'actor1',
      },
    },
  },
}}

// ✅
createMachine({
  states: {
    initializing: {
      entry: assign({
        gameRef: () => spawn(game, { systemId: 'actor1' }),
      }),
    },
  },
})