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# Stylelint Config Terra

This configuration reflects Terra's supported stylelint policy for stylesheets. It extends the  [stylelint-config-sass-guidelines](https://github.com/bjankord/stylelint-config-sass-guidelines) configuration which is based on [sass-guidelines](https://sass-guidelin.es/). Additionally, this configuration utilizes the [stylelint-no-unsupported-browser-features](https://github.com/ismay/stylelint-no-unsupported-browser-features) plugin to check if the styles used are supported by the local browserslist being targeted.

## What is Stylelint?

[Stylelint](https://stylelint.io/) is a mighty, modern CSS linter and fixer that helps you avoid errors and enforce consistent conventions in your stylesheets.

## Installation

Install the module

```shell
$ npm install stylelint --save-dev
$ npm install @cerner/stylelint-config-terra --save-dev
```

## Usage

### package.json

```json
{
  "stylelint": {
    "extends": "@cerner/stylelint-config-terra"
  }
}
```

### Extending Terra's Configuration

It is possible to specify and override the rules defined by stylelint-config-terra. Read more about it [here](https://stylelint.io/user-guide/configuration/#extends).

For example, it is possible to override the browsers specified to the no-unsupported-browser-features plugin.

```json
{
  "stylelint": {
    "extends @cerner/stylelint-config-terra",
    "rules": {
      "plugin/no-unsupported-browser-features": [
        true,
        "browsers": ["iOS >= 10"],
        "severity": "warning",
      ]
    }
  }
}
```

## Custom Lint Rules

The following custom rules are enabled by default.

* [terra/custom-property-name](/dev_tools/terra-toolkit-docs/stylelint-config-terra/custom-rules/custom-property-name): Requires custom properties to be suffixed with the css property name.
* [terra/custom-property-namespace](/dev_tools/terra-toolkit-docs/stylelint-config-terra/custom-rules/custom-property-namespace): Requires custom properties to be prefixed with a namespace.
* [terra/custom-property-no-duplication-declaration](/dev_tools/terra-toolkit-docs/stylelint-config-terra/custom-rules/custom-property-no-duplicate-declaration): Disallows a custom property to be declared more than once with a different fallback value.
* [terra/custom-property-pattern](/dev_tools/terra-toolkit-docs/stylelint-config-terra/custom-rules/custom-property-pattern): Requires custom properties to be written in lowercase alphanumeric characters and hyphens.
* [terra/custom-property-pseudo-selectors](/dev_tools/terra-toolkit-docs/stylelint-config-terra/custom-rules/custom-property-pseudo-selectors): Requires custom properties to include all ancestor pseudo selectors in order.