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Component Development

For information on how to design components, see the component design docs.

Before working with EUI components or creating new ones, you may want to run a local server for the documentation site. This is where we demonstrate how the components in our design system work.

Launching the Documentation Server

To view interactive documentation, start the development server using the command below.

yarn
yarn start

Once the server boots up, you can visit it on your browser at: http://localhost:8030/. The development server watches for changes to the source code files and will automatically recompile the components for you when you make changes.

Creating Components

There are four steps to creating a new component:

  1. Create the SCSS for the component in src/components
  2. Create the React portion of the component
  3. Write tests
  4. Document it with examples in src-docs

You can do this using Yeoman, or you can do it manually if you prefer.

Testing the component

yarn run test-unit runs the Jest unit tests once.

yarn run test-unit button will run tests with "button" in the spec name. You can pass other Jest CLI arguments by just adding them to the end of the command like this:

yarn run test-unit -- -u will update your snapshots. To pass flags or other options you'll need to follow the format of yarn run test-unit -- [arguments]. Note: if you are experiencing failed builds in Jenkins related to snapshots, then try clearing the cache first yarn run test-unit -- --clearCache.

yarn run test-unit -- --watch watches for changes and runs the tests as you code.

yarn run test-unit -- --coverage generates a code coverage report showing you how fully-tested the code is, located at reports/jest-coverage.

Refer to the testing guide for guidelines on writing and designing your tests.

Testing the component with Kibana

Note that yarn link currently does not work with Kibana. You'll need to manually pack and insert it into Kibana to test locally.

  1. In the eui folder, run npm pack. This will create a .tgz file in your EUI directory. At this point you can move it anywhere.
  2. In Kibana you have two choices:
    • Point your package.json files in Kibana to that file: "@elastic/eui": "/path/to/elastic-eui-xx.x.x.tgz" and run yarn kbn bootstrap.
    • Alternatively (and often easier), you can run yarn kbn bootstrap in Kibana first, then just unpack the .tgz file and paste its contents into an empty /kibana/node_modules/@elastic/eui folder. This method avoids having to edit all the various package.json files in Kibana if you need to run functional tests.
  3. Regardless of the method you decide run Kibana with FORCE_DLL_CREATION=true node scripts/kibana --dev to make sure it doesn't use a previously cached version of EUI.

Principles

Logically-grouped components

If a component has subcomponents (<EuiToolBar> and <EuiToolBarSearch>), tightly-coupled components (<EuiButton> and <EuiButtonGroup>), or you just want to group some related components together (<EuiTextInput>, <EuiTextArea>, and <EuiCheckBox>), then they belong in the same logical grouping. In this case, you can create additional SCSS files for these components in the same component directory.

Writing CSS

We follow Kibana's CSS style guide and SCSS style guide.

TypeScript definitions

Pass-through props

Many of our components use rest parameters and the spread operator to pass props through to an underlying DOM element. In those instances the component's TypeScript definition needs to properly include the target DOM element's props.

A Foo component that passes ...rest through to a button element would have the props interface

// passes extra props to a button
interface FooProps extends ButtonHTMLAttributes<HTMLButtonElement> {
  title: string
}

Some DOM elements (e.g. div, span) do not have attributes beyond the basic ones provided by all HTML elements. In these cases there isn't a specific *HTMLAttributes<T> interface, and you should use HTMLAttributes<HTMLDivElement>.

// passes extra props to a div
interface FooProps extends HTMLAttributes<HTMLDivElement> {
  title: string
}

If your component forwards the ref through to an underlying element, the interface is further extended with DetailedHTMLProps

// passes extra props and forwards the ref to a button
interface FooProps extends DetailedHTMLProps<ButtonHTMLAttributes<HTMLButtonElement>, HTMLButtonElement> {
  title: string
}