Bug: TestModel.getSimplePaths generates paths through guard-blocked transitions

[Ivanok]

XState version

XState version 5

Description

createTestModel(...).getSimplePaths() returns paths that pass through transitions whose guards evaluate to false. The guards are not being respected during graph traversal.

Example minimal reproduction:

const machine = createMachine({
  id: 'bug-repro',
  initial: 'start',          // <-- separate initial state is required to trigger the bug
  context: { allowed: false },
  states: {
    start: {
      on: { NEXT: 'idle' },
    },
    idle: {
      on: {
        // Guard blocks this until ALLOW has been dispatched first
        PROCEED: {
          target: 'done',
          guard: ({ context }) => context.allowed === true,
        },
        ALLOW: {
          target: 'idle',
          actions: assign({ allowed: () => true }),
        },
      },
    },
    done: { type: 'final' },
  },
});

const model = createTestModel(machine);
const paths = model.getSimplePaths({ toState: (s) => s.status === 'done' });

paths.forEach((p) => console.log(p.description));

Expected result

One path, requiring ALLOW before PROCEED

Reaches state "done"({"allowed":true}): xstate.init → NEXT → ALLOW → PROCEED

Actual result

Two paths, one of which passes through PROCEED before ALLOW has ever fired, ignoring the guard:

Reaches state "done"({"allowed":true}): xstate.init → NEXT → PROCEED → ALLOW → PROCEED
Reaches state "done"({"allowed":true}): xstate.init → NEXT → ALLOW → PROCEED

Reproduction

https://stackblitz.com/edit/github-cguebm7g?file=src%2Fmain.ts

Additional context

I have also prepared the same machine with xstate 4 and @xstate/test, which illustrates the expected result: https://stackblitz.com/edit/github-cguebm7g-hv4u2asb

[davidkpiano]

@Ivanok I made a tentative PR, but I’m reconsidering it because this may be valid default behavior.

That edge in the graph does not cease to exist just because it is currently blocked. Especially for model-based testing, it can be useful to include blocked transitions so you can verify that they are actually blocked. If a transition that is supposed to be blocked ends up taking the machine to a different state, that would indicate a bug.

I may add a filterEvents option to make enabled-only exploration easier when that is the behavior you want.