gatsby-plugin-loadable-components-ssr

Description

Server-side rendering loadable components in your gatsby application.

Installation

npm install --save gatsby-plugin-loadable-components-ssr @loadable/component

Latest version of this plugin for v2 Gatsby is 2.1.0

Latest version of this plugin for v3 Gatsby is 3.4.0

Problem

As described in the documentation a series of steps must be followed to implement server-side rendering in your app. However, it's not trivial to apply them to a gatsby application.

Solution

This plugin implements the steps described in the link above using gatsby's APIs, so you can use it only by adding gatsby-plugin-loadable-components-ssr in your list of gatsby plugins.

Usage

Simply add gatsby-plugin-loadable-components-ssr to the plugins array in gatsby-config.js.

// gatsby-config.js

module.exports = {
  plugins: [
    "gatsby-plugin-loadable-components-ssr",
    // OR
    {
      resolve: `gatsby-plugin-loadable-components-ssr`,
      options: {
        // Whether replaceHydrateFunction should call ReactDOM.hydrate or ReactDOM.render
        // Defaults to ReactDOM.render on develop and ReactDOM.hydrate on build
        useHydrate: true,
      },
    },
  ],
}

Preloading chunks

By default, this plugin will create preload tags for the chunks it creates. This can cause overeaging fetching and inaccurate prioritizing of fetching of the chunks. You can disable this behavior with the preloadTags option. You can then use a more fine-grained approach with /* webpackPreload: true */ for known above-the-fold components like heros.

  {
      resolve: "gatsby-plugin-loadable-components-ssr",
      options: {
         preloadTags: false
      },
  }

React 18 and Gatsby 5 Support

Loadable does not seem to be planning support for React 18 and Gatsby v5 will require React 18. React 18 ships with React.lazy which performs the same code-splitting + SSR that we are accomplishing here. There are no plans to write compatibility for React 18 / Gatsby 5 with this plugin, so the migration path should be one to React.lazy. This should result in an overall simpler implementation, and should be considered a positive that this plugin will no longer be needed.

My gatsby-browser.js already implements replaceHydrateFunction API

This plugin uses replaceHydrateFunction API. If your application also implements this API (gatsby-browser.js) make sure you wrap your implementation with loadableReady(() => ...).

Before (from the example in here):

// gatsby-browser.js

exports.replaceHydrateFunction = () => {
  return (element, container, callback) => {
    ReactDOM.render(element, container, callback)
  }
}

After:

// gatsby-browser.js

const loadableReady = require("@loadable/component").loadableReady

exports.replaceHydrateFunction = () => {
  return (element, container, callback) => {
    loadableReady(() => {
      ReactDOM.render(element, container, callback)
    })
  }
}

Note on Fully Dynamic Imports

While loadable does support fully dynamic imports (e.g. const MyDynamic = loadable(() => import(/components/${myComponentVar}))), the plugin currently loses the relationship between that chunk and the webpack mapping so it 404s. The workaround is here using a hardcoded 'map' component. This works well, but does not scale as well as fully dynamic as the number of components grows. There is not a plan to resolve this, as the hope is to deprecate this library when React 18 gets a stable release and you could use the React.lazy() pattern described here.