Bug: any string can be passed to `initial` or `target` fields

[tomdohnal]

XState version

XState version 5

Description

I'd expect to get TS errors for this code:

const feedbackMachine = setup({
  types: {
    context: {} as { feedback: string },
    events: {} as { type: "feedback.good" } | { type: "feedback.bad" },
  },
}).createMachine({
  context: {
    feedback: "",
  },
  initial: "NON_EXISTING_STATE", // <---- i'd expect a TS error here
  states: {
    idle: {
      on: {
        "feedback.good": {
          target: "NON_EXISTING_STATE", // <---- i'd expect a TS error here
        },
      },
    },
  },
});

Expected result

I should only be allowed to pass valid state values (in my example only idle) to the initial and target fields

Actual result

I'm allowed to pass a non existing state value to the initial and target fields, which then yields runtime errors

Reproduction

https://codesandbox.io/p/devbox/great-leavitt-fw32ld?file=%2Fsrc%2FfeedbackMachine.ts%3A10%2C69

Additional context

No response

[davidkpiano]

You're right, but that's been difficult to implement with the current XState v5 design. In the upcoming XState v6 version, we plan to make this more strictly typed.