invoke-usage.md

Enforce correct invocation of services

Enforce that the invoke property of state nodes is correctly used.

Rule Details

The invoke property used to invoke service must have an object value with a src property, which can be:

• a machine
• a function that returns a Promise
• a function that returns a "callback handler"
• a function that returns an observable
• a string, which refers to any of the 4 listed options defined in this machine's options.services

Examples of incorrect code for this rule:

// ❌ invoke must not be a function
createMachine({
  initial: 'active',
  states: {
    active: {
      invoke: () => {},
    },
  },
})

// ❌ invoke must not be a string
createMachine({
  initial: 'active',
  states: {
    active: {
      invoke: 'someService',
    },
  },
})

// ❌ invoke object must have a src property
createMachine({
  initial: 'active',
  states: {
    active: {
      invoke: {
        onDone: 'inactive',
      },
    },
  },
})

// ❌ the src property must be machine, function, string or object
createMachine({
  initial: 'active',
  states: {
    active: {
      invoke: {
        src: true,
      },
    },
  },
})

Examples of correct code for this rule:

// ✅
createMachine({
  initial: 'active',
  states: {
    active: {
      invoke: {
        src: () => {},
      },
    },
  },
})

// ✅
createMachine({
  initial: 'active',
  states: {
    active: {
      invoke: {
        src: 'someService',
      },
    },
  },
})

// ✅ "src" from a variable is fine
createMachine({
  initial: 'active',
  states: {
    active: {
      invoke: {
        src: someService,
      },
    },
  },
})