Infinite paths in @xstate/graph

[pipex]

Hi,

For state machines with context, it looks like getShortestPaths and getSimplePaths may not terminate.

For instance, the following machine

const machine = Machine<{ pings: number }>({
  initial: "ready",
  context: { pings: 0 },
  states: {
    ready: {
      on: {
        PING: {
          target: "pinging",
          actions: actions.assign({ pings: ({ pings }) => pings + 1 })
        },
        DONE: "stopped"
      }
    },
    pinging: {
      on: {
        DONE: "ready"
      }
    },
    stopped: {
      type: "final"
    }
  }
});

Since there is a loop between the states pinging and ready, I get the error too much recursion

Is this intended behavior? Any advice on how to prevent this?

Here is a link with an example sandbox
https://codesandbox.io/s/compassionate-worker-iuw01?file=/src/index.ts

[davidkpiano]

Yes, it is intended behavior. Finite states are finite; extended state (in context) can be infinite.

The overall state is a combination of finite state (ready or pinging or stopped) and extended state (count: 0 ... ∞)

You have to limit the state:

getShortestPaths(machine, {
  filter: (state) => state.context.pings < 10
})

[pipex]

Oh, that actually makes a lot of sense now that you put it that way. Thanks for the answer!

Finite states are finite; extended state (in context) can be infinite.