• module-federation-types-plugin
  • Installation
  • CLI Tool
    • CLI options
  • Plugin Configuration
    • Exposed modules
    • federation.config.json
    • webpack.config.js
    • Plugin Options
  • Consuming remote types
  • Templated Remote URLs
    • Importing from self as from remote
    • CI/CD
  • History
  • Feature comparison tables

module-federation-types-plugin

This package exposes a Webpack plugin and a node CLI command make-federated-types.

It compiles types into a dist/@types/index.d.ts file and downloads compiled remote types from other federated microapps into src/@types/remotes folder.

Global type definitions from src/@types/*.d.ts are included in compilation.

All paths can be customized to meet your environment.

Installation

npm i @cloudbeds/webpack-module-federation-types-plugin

CLI Tool

The standalone make-federated-types script compiles types to the dist/@types folder, the same way as the plugin does. It is useful for testing and debugging purposes or when it is not desired to update types automatically during the build process.

This script should not be used in CI as the build script, that executes the plugin, already writes the types.

The main requirement for the tool is the existance of a federation.config.json file.

It can be called like so:

npx make-federated-types

Or it can be added to package.json:

{
  "scripts": {
    "make-types": "make-federated-types"
  }
}

CLI options

download-federated-types

Option	Default value	Description
--webpack-config	webpack.config.js	Path to webpack config file

If the config is written in TypeScript, the script should be called with ts-node. Example:

ts-node node_modules/bin/download-federated-types --webpack-config webpack/prod.ts

make-federated-types

Option	Default value	Description
--output-types-folder, -o	dist/@types	Path to the output folder, absolute or relative to the working directory
--global-types, -g	src/@types	Path to project's global ambient type definitions, relative to the working dir
--federation-config, -c	src/@types	Path to federation.config, relative to the working dir
--tsconfig, -t	src/@types	Path to tsconfig.json, relative to the working dir
--webpack-config	webpack.config.js	Path to webpack.config.js

Plugin Configuration

Exposed modules

Create a federation.config.json that will contain the remote name and exported members. This file is mandatory for the standalone script but not required for the plugin.

Properties of this object can be used in Webpack's ModuleFederationPlugin configuration object and required by the standalone script. Example:

federation.config.json

Requirements:

• all paths must be relative to the project root
• the /index file name suffix is mandatory (without file extension)

{
  "name": "microapp-42",
  "exposes": {
    "./Button": "./src/view-layer/components/Button",
    "./Portal": "./src/view-layer/index",
    "./Http": "./src/wmf-expose/Http"
  }
}

webpack.config.js

Spread these properties into your ModuleFederationPlugin configuration and add ModuleFederationTypesPlugin to every microapp, like so:

import webpack from 'webpack';
import { ModuleFederationTypesPlugin } from '@cloudbeds/webpack-module-federation-types-plugin';

import federationConfig from '../federation.config.json';

const { ModuleFederationPlugin } = webpack.container;

module.exports = {
  /* ... */
  plugins: [
    new ModuleFederationPlugin({
      ...federationConfig,
      filename: 'remoteEntry.js',
      shared: {
        ...require('./package.json').dependencies,
      },
    }),
    new ModuleFederationTypesPlugin({
      downloadTypesWhenIdleIntervalInSeconds: 120,
    }),
  ],
}

To enable verbose logging add folowing in webpack config:

  infrastructureLogging: {
    level: 'log'
  }

Plugin Options

Setting	Value	Default	Description
dirEmittedTypes	string	@types	Path to the output folder for emitted types, relative to the distribution folder
dirGlobalTypes	string	src/@types	Path to project's global ambient type definitions, relative to the working dir
dirDownloadedTypes	string	src/@types/remotes	Path to the output folder for downloaded types
disableTypeCompilation	boolean	false	Disable compilation of types
disableDownladingRemoteTypes	boolean	false	Disable downloading of remote types
downloadTypesWhenIdleIntervalInSeconds	number, -1	60	Synchronize types continusouly - compile types after every compilation, download when idle with a specified delay value in seconds. -1 - disables continuous synchronization (compile and download will happen only on startup).
remoteEntryUrls	RemoteEntryUrls	{}	Base URLs for types. These should target compiled bundles that also contain the types. E.g. with { mfeApp: 'https://assets.mydomain.com/mfe-app' } the types will be downloaded from 'https://assets.mydomain.com/mfe-app/@types/index.d.ts'. More details available in this section
remoteManifestUrls	RemoteManifestUrls	{}	URLs to remote manifest files. A manifest contains a URL to a remote entry that is substituted in runtime. More details available in this section
moduleFederationPluginName	string	ModuleFederationPlugin	The name of the Module Federation plugin. Change this to NextFederationPlugin if you are using this plugin with @module-federation/nextjs-mf

Consuming remote types

When you build your microapp, the plugin will download typings to src/@types/remotes folder

Modules that are not intended to be imported are prefixed with #not-for-import/. These are the modules that were imported in compiled exposed modules but not listed in exposes section. To remain swift and unobtrusive, compiled types are not processed with an AST visitor like esprima. That said PRs are welcome if someone sees a better solution.

Templated Remote URLs

Templated URLs are URLs to the external remotes that are substituted in runtime using a syntax that is used in module-federation/external-remotes-plugin

Example: for a mfeApp remote entry:

{ mfeApp: 'mfeApp@[mfeAppUrl]/remoteEntry.js' }

The [mfeAppUrl] placeholder refers to window.mfeAppUrl in runtime. There are several ways one can resolve this placeholder:

• remoteEntryUrls option
• remoteManifestUrls or remoteManifestUrl option

The remoteEntryUrls option is a simple key-value map of remote names and their bundle's base URL.

Remote Manifest files

Manifest files, when provided, are fetched every time the types are downloded.

Example of a configuration:

new ModuleFederationTypesPlugin({
  remoteManifestUrls: {
    mfeApp1: 'https://localhost:4480/remotes/dev/mfe-app-1-remote-entry.json',
    mfeApp2: 'https://localhost:4480/remotes/dev/mfe-app-2-remote-entry.json',
    registry: 'https://localhost:4480/remotes/dev/remote-entries.json',
  }
})

Example with a single manifest file:

new ModuleFederationTypesPlugin({
  remoteManifestUrl: 'https://localhost:4480/remotes/dev/remote-entries.json',
})

It's expected that a JSON will contain an object with a url property:

{
  "url": "https://assets.mydomain.com/mfe-app/remoteEntry.js"
}

For the registry field in remoteManifestUrls or for the single remoteManifestUrl option, multiple remote entry URLs can be substituted in a single JSON file. Depending on your architecture, this could be the only URL that you need to specify. Example of a remote-entries.json file for a Prod environment:

[
  {
    "scope": "mfeApp1",
    "url": "https://assets.mydomain.com/mfe-app-1/remoteEntry.js"
  },
  {
    "scope": "mfeApp2",
    "url": "https://assets.mydomain.com/mfe-app-2/remoteEntry.js"
  },
  {
    "scope": "mfeApp3",
    "url": "https://assets.mydomain.com/mfe-app-3/remoteEntry.js"
  }
]

An alternative format for the manifest is an object:

{
  "mfe-app-1": "https://assets.mydomain.com/mfe-app-1/remoteEntry.js",
  "mfe-app-2": "https://assets.mydomain.com/mfe-app-2/remoteEntry.js",
  "mfe-app-3": "https://assets.mydomain.com/mfe-app-3/remoteEntry.js"
}

Note that in this case the key is converted to kebabCase and used as a scope name.

You can have registries with URLs that target bundles that was built for specific deployment environment.

The origin of the microapp's URL is used as the base URL for downloaded types

Example: https://assets.mydomain.com/mfe-app-1/@types/index.d.ts

Importing from self as from remote

It is also possible to add self as a remote entry to allow importing from self like from a remote. Example for an mfeApp microapp:

remotes: {
  mfeApp: 'mfeApp@[mfeAppUrl]/remoteEntry.js'
}

CI/CD

It is suggested to download types in a CI workflow only when a dev branch is merged to the main branch, that is the time when the deployment to dev/stage/prod is about to happen. In this case the downloaded types will correspond to the latest versions of dependent microapps, resulting in valid static type checking against other microapps code in their main branch.

When DEPLOYMENT_ENV env variable is set to devbox, remote types are not downloaded. That is to allow a microapp to download types from dev branch of another microapp. Otherwise, the build would fail on static type checking phase. A dev branch of a microapp may depend on another dev branch of another microapp, thus will have to commit those types to avoid failing workflows.

History

Having Webpack 5 module federation architecture in place it's tedious to manually create/maintain ambient type definitions for your packages so TypeScript can resolve the dynamic imports to their proper types.

While using @ts-ignore on your imports works, it is a bummer to lose intellisense and type-checking capabilities.

Inspired by several existing solutions:

• @touk/federated-types a fork of pixability/federated-types
• ruanyl/dts-loader
• ruanyl/webpack-remote-types-plugin, a wmf remotes-aware downloader of typings that can be used also with files emitted using @touk/federated-types . Example.
• @module-federation/typescript from the creator of Webpack Module Federation, Zack Jackson (aka ScriptAlchemy)

Zack Jackson was asked for help with several issues around his plugin. There was a hope that he can suggest some solutions to the exposed problems, to no avail. After a month of waiting this package was built.

Feature comparison tables

Feature	@touk/ federated-types	ruanyl/dts-loader	ruanyl/webpack-remote-types-plugin	@module-federation/typescript	@cloudbeds/webpack-module-federation-types-plugin
Webpack Plugin	-	+	+	+	+
Standalone	+	-	-	-	+
Polyrepo support	-	+	+	+	+
Runtime microapp imports	-	-	-	-	+
Support typings from node_modules	-	-	-	-	+
Webpack aliases	-	-	-	-	+
Exposed aliases	+	+	+	-	+
Excessive recompilation prevention	-	-	-	-	+

*Runtime microapp imports refers to templated remote URLs that are resolved in runtime using module-federation/external-remotes-plugin

*Synchronization refers to webpack compile hooks

*Excessive recompilation refers to the fact that the plugin is not smart enough to detect when the typings file is changed. Every time a d.ts file is downloaded, webpack recompiles the whole bundle because the watcher compares the timestamp only, which is updated on every download.

Package	Emitted destination	Download destination	Synchronization/compile hooks
@touk/federated-types	file in node_modules/@types/__federated_types	-	-
ruanyl/dts-loader	folders in .wp_federation	-	-
ruanyl/webpack-remote-types-plugin	-	types/[name]-dts	download on beforeRun and watchRun
@module-federation/typescript	folders in dist/@mf-typescript	@mf-typescript	compile and download on afterCompile (leads to double compile), redo every 1 minute when idle
@cloudbeds/webpack-module-federation-types-plugin	file in dist/@types	src/@types/remotes	download on startup with beforeRun for build mode and watchRun after first compilation in watch mode Compile afterEmit Download every 1 minute or custom interval when idle