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statelyai / xstate-tools

Public monorepo for XState tooling
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Expose`matchesStates` type through machine #169

Closed MarkBennett closed 2 years ago

MarkBennett commented 2 years ago

I'm writing a React component and want to make sure that I'm covering all possible machine states in the UX. To do this, I'm exporting the matchStates type from the typegen in the same file where I define my machine.

export type AuthMachineStates =
  import("./authMachine.typegen").Typegen0["matchesStates"];

This seems tightly coupled to the typegen implementation though, so I'd be curious if there's a safer or more reliable way to export this, or to ensure a client library is handling all possible values of state.value? Would you be open to a PR exposing this, and if so any preferences on how?

Andarist commented 2 years ago

There is already StateValueFrom type helper that you might use - however, it probably won't help you with making sure that you have covered all the cases. It sort of works but I'm worried that it might be a little bit problematic when it comes to covering parallel states and stuff.

I didn't play with it enough to be sure though. It would be best to just play with a type actually generated by the typegen to see how the narrowing works with what we produce there.

MarkBennett commented 2 years ago

Thanks @Andarist. I'll take a look at StateValueFrom as you suggest and see if that works. I've not worked too much with the never type before so this is a chance to try that out!