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gatsby-plugin-launchdarkly

A simple plugin that integrates LaunchDarkly into your Gatsby site. This will allow you to use feature flags to rollout new features on your site.

Installation

Add plugin to your Gatsby site:

npm install gatsby-plugin-launchdarkly

Then in your gatsby-config.js:

// gatsby-config.js
...
  plugins: [
    ...
    {
      resolve: 'gatsby-plugin-launchdarkly',
      options: {
        clientSideID: '<your-launchdarkly-project-client-side-id>',
        options: {
          // any LaunchDarkly options you may want to implement
          bootstrap: 'localstorage', // caches flag values in localstorage
        },
      },
    },
    ...
  ]
...

This plugin uses LaunchDarkly’s React SDK. The SDK requires a client-side ID which you can retreive from your LaunchDarkly Project settings page. This client-side ID needs to be stored in your gatsby-config.js.

Behind the scenes, this plugin will use withLDProvider to initialize the client. Read the doc on withLDProvider to understand other configuration options you can provide. As for the client options (i.e., options property), check out the documentation for how to customize your LaunchDarkly client.

Basic usage

In order to use a LaunchDarkly feature flag in your component, you’ll need to first import the LaunchDarklyContext. This plugin makes use of React Context to make the LaunchDarkly SDK available to your Gatbsy components.

import { useFlags } from 'gatsby-plugin-launchdarkly'

Then within your component, you can do the following:

// In a functional component...
const Header = ({ siteTitle }) => {
  // The following contains all of the client-side flags. Flag names are
  // automatically converted to snake-case which will allow you to pull out
  // one or more flags directly through destructuring.
  const flags = useFlags()

  return (
    <header
      style={{
        background: flags.someNewFeature ? 'green' : 'gray'
      }}
    >
...

Note that the LaunchDarkly SDK will automatically convert flag names to snake-case.

In addition to the useFlags hook, there’s also the useLDClient hook which gives you direct access to the LaunchDarkly client.

import React from 'react';
import { useFlags, useLDClient } from 'gatsby-plugin-launchdarkly';

const HooksDemo = () => {
  const { someNewFeature } = useFlags();
  const ldClient = useLDClient();

  const onLoginSuccessful = () => ldClient.identify({ key: 'aa0ceb' });

  return (
    <div>{someNewFeature ? 'Flag on' : 'Flag off'}</div>
  );
};

export default HooksDemo;

If you’re using class components, you can use the withLDConsumer higher-order component to do this instead:

import { withLDConsumer } from 'gatsby-plugin-launchdarkly'

// In your class component...
class MyComponent extends React.Component {
  render() {
    // Wrapping your class component with the withLDConsumer HOC injects the
    // flags and ldClient props into your component
    const { flags, ldClient } = this.props;

    return
      <header
        style={{
          background: flags.someNewFeature ? 'green' : 'gray'
      }}
    ...
    >
  }
}

export default withLDConsumer()(MyComponent)

The withLDConsumer HOC injects the flags and ldClient as props to your class component.

Advanced usage

This plugin assumes that the user viewing your site is anonymous — likely the case for most Gatsby sites. In this case, the LaunchDarkly SDK will uniquely track your a client so it remembers what variation of the flag was served to it. This is transparent and you don’t need to do anything else to make it work this way.

However, there might be a case where you actually have a logged in user (not an anonymous user) and you may want to let LaunchDarkly know that in case you may want to target that user for a feature. In this case, you’ll want to access the ldclient object directly:

import React from 'react';
import { useFlags, useLDClient } from 'gatsby-plugin-launchdarkly';

const HooksDemo = () => {
  const { someNewFeature } = useFlags();
  const ldClient = useLDClient();

  // Calling `identify` will cause the flags to be re-evaluated for the new
  // user that's logged in. Changes in flag values will stream in and could
  // cause your component to re-render.
  const onLoginSuccessful = (user) => ldClient.identify({
    key: user.id,
    firstName: user.firstName,
    lastName: user.lastName,
    anonymous: false,
  });

  return (
    <div>{someNewFeature ? 'Flag on' : 'Flag off'}</div>
  );
};

export default HooksDemo;

More information about changing the user context can be found here.

Contributing

This plugin is maintained and supported by LaunchDarkly. Please feel free to fork and send PRs our way.