Paragon is a pattern library containing accessible React components and a SCSS foundation built on Twitter Bootstrap. Paragon is developed for the Open edX platform.
Documentation lives at http://edx.github.io/paragon.
Paragon components require React 16 or higher. To install Paragon into your project:
In terminal:
npm i --save @edx/paragon
In your React project:
import { ComponentName } from '@edx/paragon';
Usage for Open edX and others:
index.scss
// ... Any custom SCSS variables should be defined here
@import '~@edx/paragon/scss/core/core.scss';
Usage on edx.org:
@import '~@edx/brand/paragon/fonts.scss';
@import '~@edx/brand/paragon/variables.scss';
@import '~@edx/paragon/scss/core/core.scss';
@import '~@edx/brand/paragon/overrides.scss';
Note that including fonts will affect performance. In some applications may choose not to load the custom font to keep it highly performant.
See the code of conduct.
The Paragon documentation site serves both as documentation and as a workbench to create your component within. To see your component in action, you need to run the documentation site locally. (Note you need to install dependences both in the project root and the www directory)
npm install
cd www
npm install
npm start
You can alternatively run the dev server with the edx.org theme by running
npm run develop:with-theme
Add a directory in /src/ that matches the name of your component. For example: /src/MyComponent.
Create a file src/MyComponent/index.jsx. Define your component (using the same <MyComponent> as the class name) in this file. Example:
// src/MyComponent/index.jsx
import React from 'react';
import PropTypes from 'prop-types';
const MyComponent = ({ children, className }) => {
// ...
return (
<p className={className}>
{children}
</p>
);
}
MyComponent.propTypes = {
className: PropTypes.string.isRequired,
children: Proptypes.node.isRequired,
}
export default MyComponent;Next, add your component to the exports in src/index.js. Example:
// ...
export { default as MyComponent } from './MyComponent';
// ...Create a src/MyComponent/README.md file similar to other components in the src directory. The documentation site scans this directory for markdown or mdx files to create pages.
---
title: 'MyComponent'
type: 'component'
components:
- MyComponent
categories:
- Layout
status: 'New'
designStatus: 'Done'
devStatus: 'Done'
notes: |
Something special about this component
---
### Basic Usage
```jsx live
<MyComponent>
Hello!
</MyComponent>
```
The top part of the markdown file is known as frontmatter. This metadata with consumed by the documentation site to control the title of the page and the doc site navigation.
- title controls the page title of the generated page
- components is a list of react components by displayName. This usually matches the name you define the component as in code. (In our example so far it is MyComponent). Components added to this list will be scanned by react-docgen for code comments and a props api table will be rendered at the bottom of the page.
- categories is a list of categories where this page will appear the documentation site menu.
- status, designStatus, devStatus, and notes appear in the http://localhost:8000/status page.
JSX code blocks in the markdown file can be made interactive with the live attribute. All paragon components and icons are in scope. (Note: the scope of this code block is controlled by www/components/CodeBlock.jsx).
Visit the documentation at http://localhost:8000 and navigate to see your README.md powered page and workbench. Changes to the README.md file will auto refesh the page.
Paragon runs ESLint as a pre-commit hook. If your code fails linting, you will not be able to commit. To avoid hitting a giant-wall-of-linter-failures when you try to commit, we recommend configuring your editor to run ESLint. To run ESLint in the console at any time, run the following:
$ npm run lint
Paragon's ESLint config is based off eslint-config-edx, which itself is based off eslint-config-airbnb. Paragon uses ESLint 3 (and will upgrade to v4 as soon as eslint-config-airbnb releases a supported version), which itself comes with a number of built-in rules. This configuration is highly opinionated and may contain some rules with which you aren't yet familiar, like comma-dangle, but rest assured, you're writing modern, best-practice JS 💅
One of the most powerful features of this ESLint config is its inclusion of eslint-plugin-jsx-a11y. This plugin actually enforces accessibility best practices at the linter level. It will catch things reviewers might not notice, like event handlers bound to noninteractive elements. Of course, it won't catch all accessibility violations, but it's a pretty good low-pass filter.
Paragon uses Jest with Enzyme for tests and coverage. Both libraries are full-featured and very well supported.
Jest is an all-in-one test runner and assertion library created for use with React components. Jest's API is similar to Jasmine's and comes with functionality for mocking and spying as well. Check out the docs for more details -- they are very comprehensive.
Paragon also uses Airbnb's Enzyme library to help render our components within unit tests. Enzyme comes with a number of utilities for shallow rendering, mounting components, querying the DOM, simulating DOM events, and querying React components themselves. Read the docs for more details.
To run the unit tests, run:
npm run test
To add unit tests for a component, create a file in your component's directory named <ComponentName>.test.js. Jest will automatically pick up this file and run the tests as part of the suite. Take a look at Dropdown.test.jsx or CheckBox.test.jsx for examples of good component unit tests.
To run the unit tests in the Chrome DevTools inspector, run:
npm run debug-test
Then, open chrome://inspect in your Chrome browser and select the "node_modules/.bin/jest" target to open the Chrome DevTools. You can set breakpoints in Chrome DevTools or insert a debugger; statement into the code to pause execution at that point.
Jest has built-in snapshot testing functionality which serves as a good means of smoketesting components to ensure they render in a predictable way.
When you modify components or stories (or add new components or stories), make sure to update the snapshots or else the snapshot tests will fail. It's easy to do -- just run:
$ npm run snapshot
If the snapshot tests fail, it's generally pretty easy to tell whether it's happening because of a bug or because the snapshots need to be updated. Don't be afraid to inspect the test output for clues!
Paragon measures code coverage using Jest's built-in --coverage flag and report it via Codecov. Shoot for 100% test coverage on your PRs, but use your best judgment if you're really struggling to cover those last few lines. At the very least, don't reduce total coverage. Codecov will fail your build if your PR reduces coverage.
Paragon uses the semantic-release package to automate its release process (creating Git tags, creating GitHub releases, and publishing to NPM).
Preview next release version from Pull Requests
As a convenience, the "Node.js CI / build (push)" check on Pull Requests includes a step to analyze the commit(s) and outputs a preview of what version semantic-release will publish if a PR gets merged. This is done using the "--dry-run" option for the semantic-release CLI, which will skip the publish/release steps. Look for a message in this CI step along the lines of "The next release version is <NEXT_RELEASE_VERSION>".
semantic-release analyzes commit messages to determine whether to create a major, minor, or patch release (or to skip a release).
Paragon currently uses the default conventional Angular changelog rules which means that there are 3 commit types that will trigger a release:
feat(minorrelease)fix(patchrelease)perf(patchrelease)
There are other commit types that will not trigger a release that you can use at your own discretion. Suggested prefixes are docs, chore, style, refactor, and test for non-changelog related tasks.
Any of the previous 3 commit types combined with BREAKING CHANGE in the commit message body will trigger a major version release.
perf(pencil): remove graphiteWidth option
BREAKING CHANGE: The graphiteWidth option has been removed. The default graphite width of 10mm is always used for performance reason.
Paragon is distributed on npm as ES6 modules. This means that webpack can use treeshaking on any Paragon components that a consuming app is not using, resulting in greatly reduced bundle sizes.
To get treeshaking to work, your app may require some updates - most notably, Babel 7. See this PR for an example of the changes necessary to update an app to take advantage of treeshaking with Paragon: https://github.com/edx/frontend-app-payment/pull/48