eslint-plugin-xstate

ESLint plugin to check for common mistakes and enforce good practices when using XState library.

Installation

You'll first need to install ESLint:

$ npm i eslint --save-dev

Next, install eslint-plugin-xstate:

$ npm install eslint-plugin-xstate --save-dev

Usage

Add xstate to the plugins section of your .eslintrc configuration file. You can omit the eslint-plugin- prefix:

{
  "plugins": ["xstate"]
}

Then configure the rules you want to use under the rules section.

{
  "rules": {
    "xstate/spawn-usage": "error",
    "xstate/no-infinite-loop": "error",
    "xstate/no-imperative-action": "error",
    "xstate/no-ondone-outside-compound-state": "error",
    "xstate/invoke-usage": "error",
    "xstate/entry-exit-action": "error",
    "xstate/prefer-always": "error",
    "xstate/prefer-predictable-action-arguments": "error",
    "xstate/no-misplaced-on-transition": "error",
    "xstate/no-invalid-transition-props": "error",
    "xstate/no-invalid-state-props": "error",
    "xstate/no-invalid-conditional-action": "error",
    "xstate/no-async-guard": "error",
    "xstate/event-names": ["warn", "macroCase"],
    "xstate/state-names": ["warn", "camelCase"],
    "xstate/no-inline-implementation": "warn",
    "xstate/no-auto-forward": "warn",
    "xstate/system-id": "warn"
  }
}

Shareable Configurations

This plugin exports a recommended configuration which checks for common mistakes. To enable this configuration use the extends property in your .eslintrc.js config file:

{
  "extends": ["plugin:xstate/recommended"]
}

There is also an all configuration which includes every available rule. It enforces both correct usage and best XState practices.

{
  "extends": ["plugin:xstate/all"]
}

XState Version

The default shareable configurations are for XState v5. If you use XState version 4, append _v4 to the name of the configuration you want to use.

{
  "extends": ["plugin:xstate/recommended_v4"]
}

{
  "extends": ["plugin:xstate/all_v4"]
}

If you do not use shareable configs, you need to manually specify the XState version in the ESLint config (defaults to 5):

{
  "settings": {
    "xstate": {
      "version": 4
    }
  }
}

Supported Rules

Possible Errors

Rule	Description	Recommended
spawn-usage	Enforce correct usage of spawn. Only for XState v4!	✔️
no-infinite-loop	Detect infinite loops with eventless transitions	✔️
no-imperative-action	Forbid using action creators imperatively	✔️
no-ondone-outside-compound-state	Forbid onDone transitions on atomic, history and final nodes	✔️
invoke-usage	Enforce correct invocation of services	✔️
entry-exit-action	Forbid invalid declarations of entry/exit actions	✔️
no-misplaced-on-transition	Forbid invalid declarations of on transitions	✔️
no-invalid-transition-props	Forbid invalid properties in transition declarations	✔️
no-invalid-state-props	Forbid invalid properties in state node declarations	✔️
no-async-guard	Forbid asynchronous guard functions	✔️
no-invalid-conditional-action	Forbid invalid declarations inside the choose action creator	✔️

Best Practices

Rule	Description	Recommended
no-inline-implementation	Suggest refactoring guards, actions and services into machine options
prefer-always	Suggest using the always syntax for transient (eventless) transitions	✔️
prefer-predictable-action-arguments	Suggest turning on the predictableActionArguments option	✔️
no-auto-forward	Forbid auto-forwarding events to invoked services or spawned actors
system-id	Suggest using systemId for invoked or spawned actors

Stylistic Issues

Rule	Description	Recommended
event-names	Suggest consistent formatting of event names
state-names	Suggest consistent formatting of state names and prevent confusing names

Comment Directives

By default, the plugin lints only code within the createMachine or Machine calls. However, if your machine configuration is imported from another file, you will need to enable this plugin's rules by adding a comment directive to the top of the file:

/* eslint-plugin-xstate-include */
// 💡 This machine config will now be linted too.
export const machine = {
  initial: 'active',
  context: {},
  // etc
}