Dynamic spawnChild parameters

[AntoninRousset]

I would like to access the event or context when spawning a child, in order to set a dynamic id to the child. Currently, the following does not build:

export const machine = setup({
  actors: {
    child: fromPromise(async () => {}),
  },
  types: {} as {
    context: {
      count: number;
    };
  },
}).createMachine({
  id: 'machine',
  context: { count: 0 },
  entry: spawnChild('child', ({ context }) => ({
    id: `${context.count}`;
  }),
});

A use case could be a server that spawns a machine on each request and would close the corresponding connection when a child is done by matching its id.

Currently I work around this limitation using enqueueActions:

enqueueActions(({ context, enqueue }) => enqueue.spawnChild('child', {id: `${context.count}`})

which fails to build with Type 'string' is not assignable to type 'undefined' but seems to do the job just right (once the error ignored).