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:
// ... Any custom SCSS variables should be defined here
@import "~@edx/paragon/scss/core/core.scss';
Usage on edx.org:
@import "~@edx/paragon/scss/theme/edx.scss';
If you are not using SCSS you can use the pre-built CSS.
Usage for Open edX and others:
// ... Any custom SCSS variables should be defined here
@import "~@edx/paragon/dist/paragon.css';
Usage on edx.org:
@import "~@edx/paragon/dist/edx-paragon.css";
First, clone the repo and install dependencies. You must be running Node 8 or newer.
git clone git@github.com:edx/paragon.git
cd paragon
npm install
Paragon uses Storybook to generate and serve its documentation/demo site. Storybook also serves as an excellent sandbox space to develop new components or modify existing ones. To start the Storybook server locally, run the following:
$ npm start
Storybook will be served at http://localhost:6006.
To add a new component, create a directory within /src named <ComponentName> (use UpperCamelCase, per Airbnb's React best practices). Define your component (using the same <ComponentName> as the class name) within a file in this directory named index.jsx.
To see your component in action, you will need to create a new Storybook story for it. Create a file within your component's directory named <ComponentName>.stories.js. Check out InputSelect.stories.jsx for an example of some good stories. Storybook will automatically pick up this file and serve its stories -- you should be able to see them linked from the left-hand menu.
Make sure to define PropTypes and DefaultProps on your components, using the prop-types package. PropTypes provide a clear API for your component and help consumers invoke it properly within their own code. In terms of functionality, ship an MVP component up-front. Don't make it do any more than is necessary. It's easy to add new functionality later on as needed, but it's much harder to remove functionality once we've released a component.
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. Paragon's Jest snapshots are automatically generated from components' Storybook stories using the Storyshots addon -- pretty cool, huh?
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 (which I believe uses istanbul under the hood) and report it via Coveralls. 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. Coveralls 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).
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