# eslint-plugin-promise
Enforce best practices for JavaScript promises.
[![CI](https://github.com/eslint-community/eslint-plugin-promise/actions/workflows/CI.yml/badge.svg)](https://github.com/eslint-community/eslint-plugin-promise/actions/workflows/CI.yml)
[![npm version](https://badge.fury.io/js/eslint-plugin-promise.svg)](https://www.npmjs.com/package/eslint-plugin-promise)
[![code style: prettier](https://img.shields.io/badge/code_style-prettier-ff69b4.svg)](https://github.com/prettier/prettier)
<!-- START doctoc generated TOC please keep comment here to allow auto update -->
<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
- [Installation](#installation)
- [Usage](#usage)
- [Rules](#rules)
- [Maintainers](#maintainers)
- [License](#license)
<!-- END doctoc generated TOC please keep comment here to allow auto update -->
## Installation
You'll first need to install [ESLint](http://eslint.org):
```
$ npm install eslint --save-dev
```
Next, install `eslint-plugin-promise`:
```
$ npm install eslint-plugin-promise --save-dev
```
**Note:** If you installed ESLint globally (using the `-g` flag) then you must
also install `eslint-plugin-promise` globally.
## Usage
Add `promise` to the plugins section of your `.eslintrc.json` configuration
file. You can omit the `eslint-plugin-` prefix:
```json
{
"plugins": ["promise"]
}
```
Then configure the rules you want to use under the rules section.
```json
{
"rules": {
"promise/always-return": "error",
"promise/no-return-wrap": "error",
"promise/param-names": "error",
"promise/catch-or-return": "error",
"promise/no-native": "off",
"promise/no-nesting": "warn",
"promise/no-promise-in-callback": "warn",
"promise/no-callback-in-promise": "warn",
"promise/avoid-new": "warn",
"promise/no-new-statics": "error",
"promise/no-return-in-finally": "warn",
"promise/valid-params": "warn"
}
}
```
or start with the recommended rule set:
```json
{
"extends": ["plugin:promise/recommended"]
}
```
## Rules
| rule | description | recommended | fixable |
| -------------------------------------------------------- | -------------------------------------------------------------------------------- | ----------- | -------- |
| [`catch-or-return`][catch-or-return] | Enforces the use of `catch()` on un-returned promises. | :bangbang: | |
| [`no-return-wrap`][no-return-wrap] | Avoid wrapping values in `Promise.resolve` or `Promise.reject` when not needed. | :bangbang: | |
| [`param-names`][param-names] | Enforce consistent param names and ordering when creating new promises. | :bangbang: | |
| [`always-return`][always-return] | Return inside each `then()` to create readable and reusable Promise chains. | :bangbang: | |
| [`no-native`][no-native] | In an ES5 environment, make sure to create a `Promise` constructor before using. | | |
| [`no-nesting`][no-nesting] | Avoid nested `then()` or `catch()` statements | :warning: | |
| [`no-promise-in-callback`][no-promise-in-callback] | Avoid using promises inside of callbacks | :warning: | |
| [`no-callback-in-promise`][no-callback-in-promise] | Avoid calling `cb()` inside of a `then()` (use [nodeify][] instead) | :warning: | |
| [`avoid-new`][avoid-new] | Avoid creating `new` promises outside of utility libs (use [pify][] instead) | | |
| [`no-new-statics`][no-new-statics] | Avoid calling `new` on a Promise static method | :bangbang: | :wrench: |
| [`no-return-in-finally`][no-return-in-finally] | Disallow return statements in `finally()` | :warning: | |
| [`valid-params`][valid-params] | Ensures the proper number of arguments are passed to Promise functions | :warning: | |
| [`prefer-await-to-then`][prefer-await-to-then] | Prefer `await` to `then()`/`catch()`/`finally()` for reading Promise values | :seven: | |
| [`prefer-await-to-callbacks`][prefer-await-to-callbacks] | Prefer async/await to the callback pattern | :seven: | |
| [`no-multiple-resolved`][no-multiple-resolved] | Disallow creating new promises with paths that resolve multiple times | | |
**Key**
| icon | description |
| ---------- | ----------------------------------------------- |
| :bangbang: | Reports as error in recommended configuration |
| :warning: | Reports as warning in recommended configuration |
| :seven: | ES2017 Async Await rules |
| :wrench: | Rule is fixable with `eslint --fix` |
## Maintainers
- Jamund Ferguson - [@xjamundx][]
- Macklin Underdown - [@macklinu][]
- Aadit M Shah - [@aaditmshah][]
## License
- (c) MMXV jden <mailto:jason@denizac.org> - ISC license.
- (c) 2016 Jamund Ferguson <mailto:jamund@gmail.com> - ISC license.
[catch-or-return]: docs/rules/catch-or-return.md
[no-return-wrap]: docs/rules/no-return-wrap.md
[param-names]: docs/rules/param-names.md
[always-return]: docs/rules/always-return.md
[no-native]: docs/rules/no-native.md
[no-nesting]: docs/rules/no-nesting.md
[no-promise-in-callback]: docs/rules/no-promise-in-callback.md
[no-callback-in-promise]: docs/rules/no-callback-in-promise.md
[avoid-new]: docs/rules/avoid-new.md
[no-new-statics]: docs/rules/no-new-statics.md
[no-return-in-finally]: docs/rules/no-return-in-finally.md
[valid-params]: docs/rules/valid-params.md
[prefer-await-to-then]: docs/rules/prefer-await-to-then.md
[prefer-await-to-callbacks]: docs/rules/prefer-await-to-callbacks.md
[no-multiple-resolved]: docs/rules/no-multiple-resolved.md
[nodeify]: https://www.npmjs.com/package/nodeify
[pify]: https://www.npmjs.com/package/pify
[@aaditmshah]: https://github.com/aaditmshah
[@macklinu]: https://github.com/macklinu
[@xjamundx]: https://github.com/xjamundx