# Primer CSS Development

If you've made it this far, **thank you**! We appreciate your contribution, and hope that this document helps you along the way. If you have any questions or problems, don't hesitate to [file an issue](https://github.com/primer/css/issues/new).

## Structure

Primer CSS is published to [npm] as [@primer/css]. Each of Primer CSS's "modules" lives in a subfolder under `src/` with an `index.scss` in it. Generally speaking, the styles are divided into three primary themes:

- **Core** styles (in `core/`) are common dependencies, which include support variables, native element and typography styles, buttons, navigation, tooltips, etc.
- **Product** styles (in `product/`) are specific to github.com, and include components such as avatars, labels, markdown styles, popovers, and progress indicators.
- **Marketing** styles (in `marketing/`) are specific to GitHub marketing efforts, including international and event-focused sites as well as the more design-heavy feature pages on github.com. Marketing styles include new colors and button styles, and extend the core typography and whitespace scales.

### Paths

Here's what you need to know about how the files are structured in both git and in the published npm module:

- In git, all of the SCSS source files live in the `src/` directory.
- When published, all of the files in `src/` are "hoisted" to the package root so that you can import, say, utilities with:

  ```scss
  @import '@primer/css/utilities/index.scss';
  ```

- All bundle interdependencies within Primer CSS are defined as relative imports (e.g. with `../`), so everything should work fine as long as the `@primer/css` directory is in one of your Sass include paths (i.e. `node_modules`).

## Install

Run `npm install` to install the npm dependencies.

### The docs directory

The [docs directory](../docs/) contains all of the documentation files in our docs site. Files are nested in the `/content` folder.

### Code blocks

All `html` fenced code blocks in `src/**/*.md` will be rendered as stories and listed under the relevant module's name in the left-hand nav. File changes should trigger a live reload automatically (after a brief delay).

## Storybook

Primer CSS Storybook is used for designing and prototyping components. Stories are written in HTML and leverage the Storybook API for configuring conditional logic.

```sh
npm run storybook
```

### The Storybook directory

Storybook configuration files live in [.storybook](../docs/.storybook). Addons and additional global config can be added to [main.js](../docs/.storybook/main.js) or [preview.js](../docs/.storybook/preview.js)

### Stories

Stories are individual `.jsx` or `.mdx` files that contain component HTML for prototyping, typically showcasing all possible variations of a component. Stories can be found in the [stories directory](../docs/src/stories/components) and are organized by component. Storybook will build and deploy a preview on any open Pull Request.

## Scripts

Our [`package.json`](package.json) houses a collection of [run-scripts] that we use to maintain, test, build, and publish Primer CSS. Run `npm run <script>` with any of the following values for `<script>`:

- `dist` runs `script/dist`, which creates CSS bundles of all the `index.scss` files in `src/`.
- `stylelint` lints the CSS source files.
- `eslint` lints the JavaScript source files.
- `test` runs our test suite.
- `storybook` runs storybook local development server.

The above list may not always be up-to-date. You can list all of the available scripts by calling `npm run` with no other arguments.

[@primer/css]: https://www.npmjs.com/package/@primer/css
[run-scripts]: https://docs.npmjs.com/cli/run-script
[now]: https://zeit.co/now
[npm]: https://www.npmjs.com/
[npx]: https://www.npmjs.com/package/npx