Webpack External Import

import() URLs and other external resources from third parties, or other webpack builds themselves!

$ yarn  webpack-external-import

This project is under active development

**To jump to the development section click here

Installation

npm

npm install webpack-external-import --save

Yarn

yarn add webpack-external-import --save

Getting Started

1. Add webpack-external-import/webpack to your webpack plugins:

// techblog.webpack.config.js
const URLImportPlugin = require('webpack-external-import/webpack')
{
    plugins: [
        new URLImportPlugin({
          manifestName: 'website-one'
        })
    ]
}

2. Add the import() polyfill (recommended)

// index.js
import 'webpack-external-import/polyfill';

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App.jsx';

ReactDOM.render(<App />, document.getElementById('app'));

3. If you are interleaving webpack bundles, load their manifests

  import {corsImport} from "webpack-external-import"
  // if importing on the same domain and CORS isnt an issue
  import(/* webpackIgnore:true */'http://localhost:3002/importManifest.js')

  // if you need to import from a third party where CORS is an issue
  corsImport('http://localhost:3002/importManifest.js')

4. import an external resource We use raw import() with a polyfill to act as a script loader. We also have a fallback script loader for loading CORS.

// App.jsx
// import a chunk from another website build with webpack-external-import
  import {corsImport} from "webpack-external-import"

  componentDidMount() {
      corsImport('http://localhost:3002/importManifest.js').then(() => {
        this.setState({ manifestLoaded: true });
        importDependenciesOf('http://localhost:3002', 'website-two', 'TitleComponent').then((url) => {
          this.setState({ titleUrl: url });
        });
  
        // if CORS isnt a problem, you can use native import (its polyfilled) 
        import(/* webpackIgnore:true */getChunkPath('http://localhost:3002', 'website-two', 'SomeExternalModule.js')).then(() => {
          console.log('got module, will render it in 2 seconds');
          setTimeout(() => {
            this.setState({ loaded: true });
          }, 2000);
        });
      });
    }

Or with JSX and a react component

import {ExternalComponent, getChunkPath} from 'webpack-external-import'
 render() {
    const { manifestLoaded } = this.state;

    return (
      <div>
        <HelloWorld />
        { manifestLoaded && <ExternalComponent src={getChunkPath('http://localhost:3002', 'website-two', 'TitleComponent.js')} module="TitleComponent" export="Title" title="Some Heading" />}
      </div>
    );
  }

What is the use of webpack-external-import ?

• Load components over the wire - Pull in components at runtime.
• Build leaner micro-frontends (MFE) - Micro-frontends can share bundle chunks and resources with each other while remaining self-contained, removing needless code duplication.
• Split a large, multi-team app into separate deployable chunks while keeping it as one SPA - Large apps can be split into separate feature bundles that can be deployed independently, reducing deployment bottlenecks.
• Manage common js/vendor files automatically. - Instead of dealing with peer dependencies, externals, or anything else, you can load the dependency from a remote source.
• LOSA Style frontend architecture - Run multiple apps on a single page.
• FOSA Style frontend orchestration - Powerful frontend orchestration, self-organizing application architecture. Many builds act as one

Advanced Setup - Injecting Webpack modules from another build

Use the webpack plugin to inject webpack modules from another build into your build.

Important: Make sure manifestName is unique per webpack build. If you have multiple builds, they all need to have a unique manifestName

webpack.config.js

const URLImportPlugin = require('webpack-external-import/webpack')
{
    plugins: [
        new URLImportPlugin({
          manifestName: 'website-one'
        })
    ]
}

Example Usage

Pretend we have two separate apps that each have their independent build. We want to share a module from one of our apps with the other.

To do this, we add an externalize comment to the module. The Externalize magic comment tells the plugin to make the module available externally with the name ExampleModule:

// Title.js

import React from 'react';

export 
 const Title = ({title}) => {
  return title
}

export 
 const alert = (message) => {
  alert(message)
}


/*externalize:ExampleModule*/

    
// App.js

import(/* webpackIgnore:true */'http://website1.com/js/ExampleModule.js')
.then(()=>{
  const ExampleModule = __webpack_require__("ExampleModule");
  ExampleModule.alert('custom alert')
});
    

import {
  ExternalComponent
} from 'webpack-external-import'

const SomeComponent = (props)=>{
  return (
    <ExternalComponent 
    src={
      this.state.url
    } 
    module="ExampleModule"
    export='Title' 
    title={'Some Heading'}
       />
  )
}

Explanation

Pretend we have two separate apps that each have their own independent build. We want to share a module from one of our apps with the other.

To do this, we add an externalize comment to the module. This tells the plugin to make the module available externally with the name ExampleModule and webpack will chunk this file into dist/ExampleModule.js

// Title.js

import React from 'react';

export const Title = ({title}) => {
  return (<h1>{title}</h1>)
}

export const alert = (message) => {
  alert(message)
}


/*externalize:ExampleModule*/

The ExampleModule can now be pulled into our other app using import:

import(/* webpackIgnore:true */'http://website1.com/js/ExampleModule.js').then(({ExampleModule})=>{
  ExampleModule.alert('custom alert')
});

There is also a React component, ExternalComponent, that can be useful for importing React components:

import {ExternalComponent} from 'webpack-external-import'

()=>{
  return (
    <ExternalComponent src={helloWorldUrl} module="ExampleModule" export='Title' title={'Some Heading'} cors/>
  )
}

Full Example

// WEBSITE-ONE
//app.js

import React, {Component} from 'react';
import {hot} from 'react-hot-loader';
import HelloWorld from './components/hello-world';
import {ExternalComponent,corsImport} from 'webpack-external-import'

class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      titleUrl: null,
      manifestLoaded: false,
      loaded: false,
    };
  }

  componentDidMount() {
    corsImport('http://localhost:3002/importManifest.js').then(() => {
      this.setState({ manifestLoaded: true });
      importDependenciesOf('http://localhost:3002', 'website-two', 'TitleComponent').then((url) => {
        this.setState({ titleUrl: url });
      });

      import(/* webpackIgnore:true */getChunkPath('http://localhost:3002', 'website-two', 'SomeExternalModule.js')).then(() => {
        console.log('got module, will render it in 2 seconds');
        setTimeout(() => {
          this.setState({ loaded: true });
        }, 2000);
      });
    });
  }

  renderDynamic = () => {
    const { loaded } = this.state;
    if (!loaded) return null;

    return __webpack_require__('SomeExternalModule').default();
  }

  render() {
    const { manifestLoaded, titleUrl } = this.state;
    if (!manifestLoaded) {
      return 'Loading...';
    }


    return (
      <div>
        <HelloWorld />
        {titleUrl && <ExternalComponent src={titleUrl} module="TitleComponent" export="Title" title="Some Heading" />}
        {this.renderDynamic()}
      </div>
    );
  }
}

export default App

//WEBSITE-TWO
//App.js
class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      component: null
    };
  }

  componentDidMount() {
    import('./components/hello-world').then((HelloWorld) => {
      this.setState({component: HelloWorld.default})
    })
  }

  render() {
    if (!this.state.component) return <div/>
    const {component: HelloWorld} = this.state
    return <HelloWorld title="Hello from React webpack"/>;

  }
}

export default hot(module)(App);

// Title.js

import React from 'react';

export const Title = ({title}) => {
  return (<h1>{title}</h1>)
}


/*externalize:TitleComponent*/

API:

// webpack.config.js

module.exports = {
  output: {
    publicPath
  },
  plugins: [
    new URLImportPlugin(options)
  ]
}

options.fileName

Type: String
Default: manifest.json

The manifest filename in your output directory.

options.publicPath

Type: String Default: output.publicPath

A path prefix that will be added to values of the manifest.

options.basePath

Type: String

A path prefix for all keys. Useful for including your output path in the manifest.

options.writeToFileEmit

Type: Boolean
Default: false

If set to true will emit to build folder and memory in combination with webpack-dev-server

options.seed

Type: Object
Default: {}

A cache of key/value pairs to used to seed the manifest. This may include a set of custom key/value pairs to include in your manifest or may be used to combine manifests across compilations in multi-compiler mode. To combine manifests, pass a shared seed object to each compiler's ManifestPlugin instance.

options.filter

Type: Function(FileDescriptor): Boolean

Filter out files. FileDescriptor typings

options.test

Type: Function(Object, FileDescriptor): Object
Default: src

Test resource path to see if plugin should apply transformations

options.map

Type: Function(FileDescriptor): FileDescriptor

Modify files details before the manifest is created. FileDescriptor typings

options.sort

Type: Function(FileDescriptor): number

Sort files before they are passed to generate. FileDescriptor typings

options.generate

Type: Function(Object, FileDescriptor): Object
Default: (seed, files) => files.reduce((manifest, {name, path}) => ({...manifest, [name]: path}), seed)

Create the manifest. It can return anything as long as it's serializable by JSON.stringify. FileDescriptor typings

options.serialize

Type: Function(Object): string
Default: (manifest) => JSON.stringify(manifest, null, 2)

Output manifest file in a different format then json (i.e., yaml).

ExternalComponent

React Component

Props:

src: string - Import source URL

module: string - Module name, must match what was declared using /externalize:ExampleModule/

export: string - The named export to use as a component from the module being imported

cors: bool - If asset is being loaded from a url which throws a CORS error. This will inject a script to the browser

Usage

<ExternalComponent src={helloWorldUrl} module="ExampleModule" export='Title' title={'Some Heading'}/>

FileDescriptor

FileDescriptor {
  path: string;
  name: string | null;
  isInitial: boolean;
  isChunk: boolean;
  chunk?: Chunk;
  isAsset: boolean;
  isModuleAsset: boolean;
}

The entry manifest

Each webpack build using the webpack plugin emits a manifest file to the build output directory.

The manifest allows you to find a chunk that you want, even if the name has been hashed.

Below is an example of using the manifest.

In this file, I am importing code from another website/build. My application is loading website two's manifest, which is automatically added to window.entryManifest under the manifestName I set in the webpack plugin. After that, I'm importing a chunk from website-two, in this case - the chunk is code-split.

    componentDidMount() {
      corsImport('http://localhost:3002/importManifest.js').then(() => {
        this.setState({ manifestLoaded: true });
        importDependenciesOf('http://localhost:3002', 'website-two', 'TitleComponent').then((url) => {
          this.setState({ titleUrl: url });
        });
  
        import(/* webpackIgnore:true */getChunkPath('http://localhost:3002', 'website-two', 'SomeExternalModule.js')).then(() => {
          console.log('got module, will render it in 2 seconds');
          setTimeout(() => {
            this.setState({ loaded: true });
          }, 2000);
        });
      });
    }

DEMO

How to start using the demo In the root directory, run the following

1. run yarn install
2. run yarn demo from the root directory
3. browse to localhost:3001 or localhost:3002

This command will install, all dependencies, build the source for the plugin, install the demo dependencies, run all builds and start serving

Development & Debugging

How to start the demo in debug mode, using node --inspect and connecting to a chrome debugger

This is mainly for debugging the webpack plugin

In the root directory, run the following

1. yarn install
2. yarn demo:debug from the root directory
3. browse to localhost:3001 or localhost:3002

Note: localhost:3001 is the "consumer app, while the other is the provider app". Both apps work independently and you should check both of them out (they are extremely basic)

Open chrome dev tools and you should see the box highlighted below appear, click on it to connect to the webpack debugger