consuming-eui

Consuming EUI

Installation

To install the Elastic UI Framework into an existing project, use the yarn CLI (npm is not supported).

yarn add @elastic/eui

Note that EUI has several peerDependencies requirements that will also need to be installed if starting with a blank project.

yarn add @elastic/eui @elastic/datemath @emotion/react @emotion/css moment

Requirements and dependencies

EUI expects that you polyfill ES2015 features, e.g. babel-polyfill. Without an ES2015 polyfill your app might throw errors on certain browsers.

EUI also has moment and @elastic/datemath as dependencies itself. These are already loaded in most Elastic repos, but make sure to install them if you are starting from scratch.

What's available

EUI publishes React UI components, JavaScript helpers called services, and utilities for writing Jest tests. Please refer to the Elastic UI Framework website for comprehensive info on what's available.

EUI is published through NPM as a dependency. We also provide a starter projects for:

• GatsbyJS
• NextJS

Components

You can import React components from the top-level EUI module.

import {
  EuiButton,
  EuiCallOut,
  EuiPanel,
} from '@elastic/eui';

Test

Test utilities are published from the lib/test directory.

import { findTestSubject } from '@elastic/eui/lib/test'; // Enzyme
import { findByTestSubject, render, screen } from '@elastic/eui/lib/test/rtl'; // React Testing Library

Theming

EUI uses CSS-in-JS (specifically Emotion) for its styles and theming. As such, we require an <EuiProvider> wrapper around your application in order for various theme-related UI & UX (such as dark/light mode switching) to work as expected.

import React from 'react';

import { EuiProvider, EuiText } from '@elastic/eui';

const MyApp = () => (
  <EuiProvider>
    <EuiText><p>Hello World!</p></EuiText>
  </EuiProvider>
);

export default MyApp;

Consuming theme tokens

Using EUI's theme layer with Emotion is documented in our docs and should cover the majority of your theming needs.

import { useEuiTheme } from '@elastic/eui';
import { css } from '@emotion/react';

export default () => {
  const { euiTheme } = useEuiTheme();
  const styles = css`
    color: ${euiTheme.colors.primary};
    border: ${euiTheme.border.thin};
    padding: ${euiTheme.size.s};
  `;
  return (
    <div css={styles} />
  );
};

"Module build failed" or "Module parse failed: Unexpected token" error

If you get an error when importing a React component, you might need to configure Webpack's resolve.mainFields to ['webpack', 'browser', 'main'] to import the components from lib instead of src. See the Webpack docs for more info.

Failing icon imports

To reduce EUI's impact to application bundle sizes, the icons are dynamically imported on-demand. This is problematic for some bundlers and/or deployments, so a method exists to preload specific icons an application needs.

import { appendIconComponentCache } from '@elastic/eui/es/components/icon/icon';

import { icon as EuiIconArrowDown } from '@elastic/eui/es/components/icon/assets/arrow_down';
import { icon as EuiIconArrowLeft } from '@elastic/eui/es/components/icon/assets/arrow_left';

// One or more icons are passed in as an object of iconKey (string): IconComponent
appendIconComponentCache({
  arrowDown: EuiIconArrowDown,
  arrowLeft: EuiIconArrowLeft,
});

Using the test-env build

EUI provides a separate babel-transformed and partially mocked commonjs build for testing environments in consuming projects. The output is identical to that of lib/, but has transformed async functions and dynamic import statements, and also applies some useful mocks. This build mainly targets Kibana's Jest environment, but may be helpful for testing environments in other projects.

Mapping to the test-env directory

In Kibana's Jest configuration, the moduleNameMapper option is used to resolve standard EUI import statements with test-env aliases.

moduleNameMapper: {
  '@elastic/eui$': '<rootDir>/node_modules/@elastic/eui/test-env'
}

This eliminates the need to polyfill or transform the EUI build for an environment that otherwise has no need for such processing.

Mocked component files

Besides babel transforms, the test environment build consumes mocked component files of the type src/**/[name].testenv.*. During the build, files of the type src/**/[name].* will be replaced by those with the testenv namespace. The purpose of this mocking is to further mitigate the impacts of time- and import-dependent rendering, and simplify environment output such as test snapshots. Information on creating mock component files can be found with testing documentation.

Using the optimize build (Beta)

The optimize output directory is an opt-in intermediate step as we work towards dedicated, formal build output for development and production environments.

When compiling with webpack, use the resolve.alias configuration to target the desired directory:

resolve: {
  alias: {
    '@elastic/eui$': '@elastic/eui/optimize/lib'
  }
}

Designated "Beta" as included babel plugins may change and the output directory is likely to be renamed.

Notable differences

• Absence of propTypes
  • Significant bundle size decrease
  • Likely not suitable for development environments
• Runtime transforms
  • Slight bundle size decrease
  • Requires @babel/runtime be a consumer dependency