[core] Ensure root node gets included in configuration for entry/exit actions

[davidkpiano]

Fixes #2147, fixes #2176

[changeset-bot]

🦋 Changeset detected

Latest commit: 47b9af5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
xstate	Patch

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[davidkpiano]

@Andarist Ready for final review

[Andarist]

Observation: before investigating #2176 I had a mental model of us adding an "implied" root node but I've realized here that it cannot be seen as such without overcomplicating abstract logic for final states. What we do (in contrast to SCXML) is that we allow <scxml> to work more closely to <state>/<parallel> - by allowing, for example, transitions to be defined for it. If we plan to support XState -> SCXML conversion then this should be accounted for as wrapping the whole thing in that extra "implied" root node would just not cut it.

Question: what should be the value of a combinatorial machine?

[davidkpiano]

Question: what should be the value of a combinatorial machine?

Just an object: {}

[Andarist]

Isn't this looking slighty weird?

// value: {}
createmachine({})

// value: 'a'
createMachine({
  initial: 'a',
  states: {
    a: {}
  }
})

// value: { a: 'b' }
createMachine({
  initial: 'a',
  states: {
    a: {
      initial: 'b',
      states: {
        b: {}
      }
    }
  }
})

[VanTanev]

Do you think the second one should be: { a: {} }?

[davidkpiano]

Do you think the second one should be: { a: {} }?

Maybe in version 5 🤔 that's not a bad idea.