# Neutrino Airbnb Base Preset

`@neutrinojs/airbnb-base` is a Neutrino preset that supports linting JavaScript
projects with Airbnb's base ESLint config, following the
[Airbnb styleguide](https://github.com/airbnb/javascript).

[![NPM version][npm-image]][npm-url] [![NPM downloads][npm-downloads]][npm-url]

## Features

- Zero upfront configuration necessary to start linting your project
- Modern Babel knowledge supporting ES modules, JSX (when used with React
  preset), Web and Node.js apps
- Highly visible during development, fails compilation when building for
  production
- Easily extensible to customize your project as needed

_Note: If you are building a React project, you should probably use
[`@neutrinojs/airbnb`](https://www.npmjs.com/package/@neutrinojs/airbnb)
instead._

## Requirements

- Node.js 10+
- Yarn v1.2.1+, or npm v5.4+
- Neutrino 9 and one of the Neutrino build presets
- webpack 4
- ESLint 6 or 7

## Quickstart

The fastest way to get started is by using the `create-project` scaffolding
tool. See the
[Create new project](https://neutrinojs.org/installation/create-new-project/)
docs for more details.

Don’t want to use the CLI helper? No worries, we have you covered with the
[manual installation](#manual-installation).

## Manual Installation

First follow the manual installation instructions for your chosen build preset.

`@neutrinojs/airbnb-base` can be installed via the Yarn or npm clients. Inside
your project, make sure `@neutrinojs/airbnb-base` and `eslint` are development
dependencies. You will also be using another Neutrino preset for building your
application source code.

#### Yarn

```bash
❯ yarn add --dev @neutrinojs/airbnb-base eslint
```

#### npm

```bash
❯ npm install --save-dev @neutrinojs/airbnb-base eslint
```

After that, edit your project's `.neutrinorc.js` to add the preset for linting
**before** your build preset. For example, when building your project using
`@neutrinojs/web`:

```js
const airbnbBase = require('@neutrinojs/airbnb-base');
const web = require('@neutrinojs/web');

module.exports = {
  options: {
    root: __dirname,
  },
  use: [airbnbBase(), web()],
};
```

Start the app, then check your console for any linting errors. If everything is
successful, you should see no errors in the console. ESLint errors visible
during development are reported, but will still continue to build and serve your
project. ESLint errors during build will not build the project, and will cause
the command to fail.

#### Yarn

```bash
❯ yarn start

ERROR in ./src/index.js
Module Error (from ./node_modules/eslint-loader/index.js):

error: Missing semicolon (semi) at src/index.js:35:51:
  33 |
  34 |
> 35 | const MOUNT_NODE = document.getElementById("root")
     |                                                   ^
  36 |
  37 |
  38 |

1 error found.
1 error potentially fixable with the `--fix` option.
```

#### npm

```bash
❯ npm start

ERROR in ./src/index.js
Module Error (from ./node_modules/eslint-loader/index.js):

error: Missing semicolon (semi) at src/index.js:35:51:
  33 |
  34 |
> 35 | const MOUNT_NODE = document.getElementById("root")
     |                                                   ^
  36 |
  37 |
  38 |

1 error found.
1 error potentially fixable with the `--fix` option.
```

## Project Layout

`@neutrinojs/airbnb-base` follows the standard
[project layout](https://neutrinojs.org/project-layout/) specified by Neutrino.
This means that by default all project source code should live in a directory
named `src` in the root of the project.

## Building

`@neutrinojs/airbnb-base` will cause errors to **fail your build** when
`NODE_ENV` is not `'development'`. If you want to ease introduction of this
linting preset to your project, consider only adding it to your `use` list
during development until all linting errors have been resolved.

```bash
❯ yarn build

ERROR in ./src/index.js
Module Error (from ./node_modules/eslint-loader/index.js):

error: Missing semicolon (semi) at src/index.js:35:51:
  33 |
  34 |
> 35 | const MOUNT_NODE = document.getElementById("root")
     |                                                   ^
  36 |
  37 |
  38 |

1 error found.
1 error potentially fixable with the `--fix` option.
```

_Example: ease linting into project by only enabling when `NODE_ENV=development`
(ie: `--mode development`):_

```js
const airbnbBase = require('@neutrinojs/airbnb-base');
const web = require('@neutrinojs/web');

module.exports = {
  options: {
    root: __dirname,
  },
  use: [process.env.NODE_ENV === 'development' ? airbnbBase() : false, web()],
};
```

## Middleware options

This preset uses the same middleware options as
[@neutrinojs/eslint](https://neutrinojs.org/packages/eslint/#usage). If you wish
to customize what is included, excluded, or any ESLint options, you can provide
an options object with the middleware and this will be merged with our internal
defaults for this preset.

_Example: Extend from a custom configuration (it will be applied after Airbnb)
and turn off semicolons from being required._

```js
const airbnbBase = require('@neutrinojs/airbnb-base');

module.exports = {
  options: {
    root: __dirname,
  },
  use: [
    airbnbBase({
      eslint: {
        // For supported options, see:
        // https://github.com/webpack-contrib/eslint-loader#options
        // https://eslint.org/docs/developer-guide/nodejs-api#cliengine
        // The options under `baseConfig` correspond to those
        // that can be used in an `.eslintrc.*` file.
        baseConfig: {
          extends: ['my-custom-config'],
          rules: {
            'babel/semi': 'off',
          },
        },
      },
    }),
  ],
};
```

## Exposing generated lint configuration via `.eslintrc.js`

`@neutrinojs/eslint`, from which this preset inherits, provides an `.eslintrc()`
output handler for generating the ESLint configuration in a format suitable for
use in an `.eslintrc.js` file. This allows the ESLint CLI to be used outside of
building the project, and for IDEs and text editors to provide linting
hints/fixes.

Create a `.eslintrc.js` file in the root of the project, containing:

```js
// .eslintrc.js
const neutrino = require('neutrino');

module.exports = neutrino().eslintrc();
```

This `.eslintrc.js` configuration will be automatically used when running the
ESLint CLI. For convenience a `lint` script alias can be added to your
`package.json`, allowing linting to be run via `yarn lint` or `npm run lint`:

```json
{
  "scripts": {
    "lint": "eslint --cache --format codeframe --ext mjs,jsx,js src"
  }
}
```

Projects may face a problem when their editor or IDE lints all files and
highlights errors that were normally excluded from source, i.e. Neutrino's
`include` and `exclude` options. This is because the ESLint CLI does not have a
way to specify included and excluded files from the `.eslintrc.js`
configuration. Instead you will need to create an
[.eslintignore](https://eslint.org/docs/user-guide/configuring#ignoring-files-and-directories)
file that controls which files should be excluded from linting.

## Using your own `.eslintrc.*`

If instead you would prefer to use your own non-generated `.eslintrc.*` file,
set `useEslintrc` to `true`. This will cause `@neutrinojs/airbnb-base` to only
set the loader-specific configuration defaults, and leave all other linting
configuration to be managed by the standalone `.eslintrc.*` file.

See the `@neutrinojs/eslint`
[documentation](https://neutrinojs.org/packages/eslint/#using-your-own-eslintrc)
for more details.

## Customizing

To override the lint configuration, start with the documentation on
[customization](https://neutrinojs.org/customization/).
`@neutrinojs/airbnb-base` creates some conventions to make overriding the
configuration easier once you are ready to make changes.

### Rules

The following is a list of rules and their identifiers which can be overridden:

| Name   | Description                                                                                                                                                                  | NODE_ENV |
| ------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------- |
| `lint` | By default, lints JS and JSX files from the `src` and `test` directories using ESLint. Contains a single loader named `eslint`. This is inherited from `@neutrinojs/eslint`. | all      |

## Contributing

This preset is part of the [neutrino](https://github.com/neutrinojs/neutrino)
repository, a monorepo containing all resources for developing Neutrino and its
core presets and middleware. Follow the
[contributing guide](https://neutrinojs.org/contributing/) for details.

[npm-image]: https://img.shields.io/npm/v/@neutrinojs/airbnb-base.svg
[npm-downloads]: https://img.shields.io/npm/dt/@neutrinojs/airbnb-base.svg
[npm-url]: https://www.npmjs.com/package/@neutrinojs/airbnb-base