# 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`). ## Workflow The typical Primer workflow looks something like this: 1. `npm install` to install the development dependencies. 1. [Start Storybook](#storybook) 1. Navigate to the module you're working on and modify the SCSS and/or markdown files. 1. Test your changes in Storybook. 1. Push your work to a new branch. 1. Request a review from one of the Primer "core" team members. ## Install Run `npm install` to install the npm dependencies. ## Docs site The Primer CSS docs are built with React using [Primer Components](https://primer.style/components) and automatically deployed on every push to this repo with [Now]. You can run the server locally with: ```sh npm start ``` Then visit http://localhost:3000/css to view the site. :rotating_light: **Warning:** Next.js has a [long-running issue](https://github.com/zeit/next.js/issues/1189) with trailing slashes in URLs. Avoid visiting `http://localhost:3000/` if possible, as this may cause your development server to fail in less-than-graceful ways. ### The pages directory The [pages directory](./pages/) contains all of the documentation files that map to URLs on the site. Because we host the site at `primer.style/css` (and because of the way that Now's path aliasing feature works), we nest all of our documentation under the [css subdirectory](./pages/css). ### URL tests We have a script that catches inadvertent URL changes caused by renaming or deleting Markdown docs: ```sh npm run test-urls ``` This script includes some exceptions for URLs that have been intentionally moved or removed in the process of moving away from the [GitHub Style Guide](https://styleguide.github.com/primer/), and which you will need to modify if you rename or remove either Markdown docs or their `path` frontmatter. See [#641](https://github.com/primer/css/pull/641) for more information. ## Storybook To borrow a [metaphor from Brad Frost](http://bradfrost.com/blog/post/the-workshop-and-the-storefront/), the [docs site](#docs-site) is Primer CSS's storefront, and [Storybook] is its workshop. Our Storybook setup allows you to view every HTML code block in Primer CSS's Markdown docs in isolation. To get started, run the Storybook server with: ```sh npm run start-storybook ``` This should open up the site in your browser (if not, navigate to `http://localhost:8001`). ### 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). ## 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