entry-exit-action.md

Forbid invalid entry/exit actions declarations

Enforce valid declarations of entry and exit actions.

Rule Details

It is easy to mistake entry/exit action declarations with transition declarations, especially when user wishes to declare a conditional action. Valid entry/exit actions are:

• a function
• an action creator call
• an action object
• a string, which refers to any of the above in this machine's options.actions
• a variable, which refers to any of the above
• an array with any of the above elements

Most notably, an action is not an object with a cond property:

// ❌ this is a transition, not action declaration
{
  entry: {
    cond: 'someGuard',
    actions: 'someAction'
  }
}

Examples of incorrect code for this rule:

// ❌ confused transitions with actions
createMachine({
  entry: [
    {
      cond: 'someGuard',
      actions: 'someAction',
    },
    {
      actions: 'defaultAction',
    },
  ],
})

// ❌ invalid entry/exit action values
createMachine({
  entry: 123, // numbers are invalid
  exit: {}, // objects without a "type" property are invalid
})

// ❌ array od invalid action values
createMachine({
  entry: [123, {}, { actions: 'someAction' }],
})

Examples of correct code for this rule:

// ✅ using valid action values
createMachine({
  entry: 'someAction',
  exit: ['someAction', () => {}, assign({ foo: true }), someAction],
})

// ✅ declare conditional actions with "choose"
createMachine({
  entry: choose([
    {
      cond: 'someGuard',
      actions: 'someAction',
    },
    {
      actions: 'defaultAction',
    },
  ]),
})

// ✅ alternatively, declare conditional/dynamic actions with "pure"
createMachine({
  entry: pure((ctx) => {
    const actions = []
    // your conditional logic here
    // if (someCondition) actions.push('someAction')
    return actions
  }),
})