Plugins and loaders for webpack used with Dojo
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This repository contains all of the custom Webpack plugins and loaders used by @dojo/cli-build-app and @dojo/cli-build-widget to facilitate building Dojo 2 applications and widgets, respectively.


To use @dojo/webpack-contrib in a single project, install the package:

npm install @dojo/webpack-contrib



A webpack loader that injects CSS module path information into the generated modules, making it easier for @dojo/widget-core to resolve theme styles. This loader takes no options.


A webpack loader that generates .d.ts files for CSS modules. This is used by both @dojo/cli-build-app and @dojo/cli-build-widget to provide in-widget type checks for CSS classes.

The loader expects the following options:

Property Type Optional Description
type 'ts' or 'css' No The type of file being processed. If ts, the loader assumes the resource is a TypeScript file and will parse it for CSS module imports. If any CSS modules are found, then the loader generates a d.ts file for each. If css is specified, then the loader assumes the resource is a CSS module and generates the .d.ts file for it.
instanceName string Yes An optional instance name for the TypeScript compiler created by the ts-loader. This option is valid only when the type is ts, and ensures the same compiler instance is used across all files.


const webpackConfig = {
	loaders: [
		// Generate `.d.ts` files for all CSS modules imported in TypeScript files beneath
		// the `src/` directory
			include: './src/',
			test: /\.ts$/,
			enforce: 'pre',
			loader: '@dojo/webpack-contrib/css-module-dts-loader?type=ts&instanceName=APP_NAME'
		// Generate `.d.ts` files for all CSS modules beneath the `src/` directory
			include: './src/',
			test: /\.m\.css$/,
			enforce: 'pre',
			loader: '@dojo/webpack-contrib/css-module-dts-loader?type=css'


A webpack loader that returns a promise from require() calls that resolves to the requested resource. It also removes absolute paths from source maps, ensuring consistent builds across environments. It is used by @dojo/cli-build-app for lazily loading bundles.

This loader expects two parameters, one required and one optional:

  1. The required promise implementation (e.g., bluebird). If there already exists a global Promise constructor, then global should be specified.
  2. An optional chunk name.


const resourcePromise = require('@dojo/webpack-contrib/promise-loader?global,resource-chunk-name!./path/to/resource');
resourcePromise.then((resource) => {
	// resource is available


A webpack loader which allows code to be statically optimized for a particular context at bundling time. This loader acts on JavaScript. Some examples show the TypeScript source, but the loader will only work if acting on the compiled output.


The loader examines code, looking for usages of @dojo/has or has pragmas to optimize. It does this by parsing the AST structure of the code, and modifying it when appropriate.

The loader takes two options:

  • features: A map of static features or a feature or list of features that resolve to a similar static map based on the functionality provided by the specified targets. Each key in the map is the name of the feature and the value is true if the feature is present in that context, otherwise false.
  • isRunningInNode: An optional boolean parameter. If set to false this indicates that the loader will not be running in an environment with a Node-like require.

For example in a webpack configuration, the map of features would look like this:

    use: [
            loader: '@dojo/webpack-contrib/static-build-loader',
            options: {
                features: {
                    'foo': true,
                    'bar': false

This asserts feature foo is true and feature bar is false. Alternatively a list of features can be provided that will be resolved to the appropriate map

	use: [
			loader: '@dojo/webpack-contrib/static-build-loader',
			options: {
				features: [ 'firefox', 'chrome' ]

Available features

When specifying a static map, any values can be used. When passing a string or list of strings, the following values are supported. Each value corresponds to the set of known features that the environment supports. If multiple features are specified, the intersection of available features will be returned.

  • android
  • chrome
  • edge
  • firefox
  • ie11
  • ios
  • node
  • node8
  • safari

In either case, the resulting map is then used in the features below.

Dead Code Removal

The loader assumes that the @dojo/has API is being used in modules that are being compiled into a webpack bundle and attempts to rewrite calls to the has() API when it can see it has a statically asserted flag for that feature.

The loader detects structures like the following in transpiled TypeScript modules:

import has from './has';

if (has('foo')) {
    console.log('has foo');
else {
    console.log('doesn\'t have foo');

const bar = has('bar') ? 'has bar' : 'doesn\'t have bar';

And will rewrite the code (given the static feature set above), like:

import has from './has';

if (true) {
    console.log('has foo');
else {
    console.log('doesn\'t have foo');

const bar = false ? 'has bar' : 'doesn\'t have bar';

When this is minified via Uglify via webpack, Uglify looks for structures that can be optimised and would re-write it further to something like:

import has from './has';

console.log('has foo');

const bar = 'doesn\'t have bar';

Any features which are not statically asserted, are not re-written. This allows the code to determine at run-time if the feature is present.

Elided Imports

The loader looks for has pragmas, which are strings that contain a call to has for a specific feature, and removes the next import found in the code. For example, given the above feature set, which has foo = true and bar = false, the imports of 'a' and 'b' would be removed but 'c' and 'd' would remain.

const statementBeforeImport = 3;
// This is the next import so it will be removed despite
// the conetnet between it and the pragma
import 'a';
// The pragma can be negated to remove the import if the condition
// is known to be false
import 'b';
// This import will not be removed because `foo` is not false
import 'c';

// This import will not be removed because the value of `has('baz')`
// is now known statically
import 'd';



A webpack plugin that generates a bundle's HTML and inlines critical CSS at build time. This is similar to server-side rendering, but does not require a dedicated server to manage it.

The plugin takes an options object with the following properties:

Property Type Optional Description
entries string[] No The entry scripts to include in the generated HTML file
paths string[] or { path: string; match: string[] } Yes An array of paths that will be matched against the URL hash, rendering the HTML associated with any matched path. If the path is a string, then it will be compared directly to window.location.hash. If the path is an object, then it should include a path string that will be used to resolve the HTML, and match string array that represents multiple paths that should trigger the path to be rendered. Defaults to an empty array ('[]').
root string Yes The ID for the root HTML element. If falsy, then no HTML will be generated. Defaults to an emtpy string ('').
useManifest boolean Yes Determines whether a manifest file should be used to resolve the entries. Defaults to false.


Beyond the plugin itself, it is also beneficial to include the @dojo/webpack-contrib/build-time-render/hasBuildTimeRender module in the entry config option. This file adds the has('build-item-render') flag that applications can use to determine whether the app has been pre-rendered.

The following example will generate an HTML file containing <script> tags for the specified entries, along with the critical CSS and HTML for the root, #account, and #help paths. Both the #faq and #contact hashes will display the #help HTML.

import BuildTimeRender from '@dojo/webpack-contrib/build-time-render/BuildTimeRender';

const entry = {
	main: {

const webpackConfig = {
	plugins: [
		new BuildTimeRender({
			entries: Object.keys(entry),
			paths: [
				{ path: '#help', match: [ 'faq', 'contact' ] }
			root: 'app',
			useManifest: true


A webpack plugin that converts .m.css import paths to .m.css.js. This is used in conjunction with the css-module-dts-loader loader to ensure that webpack can probably resolve CSS module paths.

If the requested resource uses a relative path, then its path will be resolved relative to the requesting module. Otherwise, the resource will be loaded from ${basePath}node_modules (see below for the definition of basePath):

// Path is relative to the current module
import * as localCss from './path/to/local-styles.m.css';

// Imported from node_modules
import * as externalCss from 'some-mid/styles.m.css';

The plugin constructor accepts a single argument:

Property Type Optional Description
basePath string No The root path from which to resolve CSS modules


External libraries that cannot be loaded normally via webpack can be included in a webpack build using this plugin.

The plugin takes an options object with the following properties:

Property Type Optional Description
dependencies ExternalDep[] No External dependencies to load. Described in more detail below
hash boolean Yes Whether to use the build's hash to cache bust injected dependencies
outputPath string Yes Where to copy dependencies to; defaults to "externals"
pathPrefix string Yes Used to change the directory where files are placed(e.g. placing files in _build for testing)

All external dependencies specified in the dependencies options will be placed in ${pathPrefix}/${outputPath}. Each ExternalDep in the dependencies array specifies one external dependency. Each can be a string, indicating a path that should be delegated to the configured loader, or an object with the following properties:

Property Type optional Description
from string false A path relative to the root of the project specifying the dependency location to copy into the build application.
to string true A path that replaces from as the location to copy this dependency to. By default, dependencies will be copied to ${externalsOutputPath}/${to} or ${externalsOutputPath}/${from} if to is not specified. If the path includes . characters, it must end in a forward slash to be treated as a directory
name string true Indicates that this path, and any children of this path, should be loaded via the external loader
inject string, string[], or boolean true This property indicates that this dependency defines, or includes, scripts or stylesheets that should be loaded on the page. If inject is set to true, then the file at the location specified by to or from will be loaded on the page. If this dependency is a folder, then inject can be set to a string or array of strings to define one or more files to inject. Each path in inject should be relative to ${externalsOutputPath}/${to} or ${externalsOutputPath}/${from} depending on whether to was provided.


Rather than manually set locale data within an application's entry point, that data can instead be read from a config and injected in at build time.

The plugin accepts an options object with the following properties:

Property Type Optional Description
cldrPaths string[] Yes An array of paths to CLDR JSON modules that should be included in the build and registered with the i18n ecosystem. If a path begins with a ".", then it is treated as relative to the current working directory. Otherwise, it is treated as a valid mid.
defaultLocale string No The default locale.
supportedLocales string[] Yes An array of supported locales beyond the default.
target string Yes The entry point into which the i18n module should be injected. Defaults to src/main.ts.

A custom module is generated from the locale data, injected into the bundle, and then imported into the specified entry point. The user's locale is compared against the default locale and supported locales, and if it is supported is set as the root locale for the application. If the user's locale is not supported, then the default locale is used. For example, the user's locale will be used in the following scenarios:

The user's locale can be represented by the default locale:

  • Default Locale: 'en'
  • Supported Locales: none
  • User's locale: 'en-US'

The user's locale can be represented by one of the supported locales:

  • Default Locale: 'en'
  • Supported Locales: [ 'fr' ]
  • User's locale: 'fr-CA'

However, in the following scenario the default locale will be used, although it still will be possible to switch between any of the supported locales at run time, since their required data will also be included in the build:

  • Default Locale: 'en'
  • Supported Locales: [ 'de', 'ja', 'ar' ]
  • User's locale: 'cz'


A custom webpack plugin that generates a service worker from configuration options, or simply ensures a custom service worker is copied to the output directory. Generated service workers support both precaching and runtime caching and allow you specify additional resources that should be loaded by the service worker.

The plugin accepts either a string path for an existing service worker to copy to the output directory, or an options object with the following properties:

Property Type Optional Description
bundles string[] Yes An array of bundles to include in the precache. Defaults to all bundles.
cachePrefix string Yes The prefix to use for the runtime precache cache.
clientsClaim boolean Yes Whether the service worker should start controlling clients on activation. Defaults to false.
excludeBundles string[] Yes An array of bundles to include in the precache. Defaults to [].
importScripts string[] Yes An array of script paths that should be loaded within the service worker
precache object Yes An object of precache configuration options (see below)
routes object[] Yes An array of runtime caching config objects (see below)
skipWaiting boolean Yes Whether the service worker should skip the waiting lifecycle


The precache option can take the following options to control precaching behavior:

Property Type Optional Description
baseDir string Yes The base directory to match include against.
ignore string[] Yes An array of glob pattern string matching files that should be ignored when generating the precache. Defaults to [ 'node_modules/**/*' ].
include string or string[] Yes A glob pattern string or an array of glob pattern strings matching files that should be included in the precache. Defaults to all files in the build pipeline.
index string Yes The index filename that should be checked if a request fails for a URL ending in /. Defaults to 'index.html'.
maxCacheSize number Yes The maximum size in bytes a file must not exceed to be added to the precache. Defaults to 2097152 (2 MB).
strict boolean Yes If true, then the build will fail if an include pattern matches a non-existent directory. Defaults to true.
symlinks boolean Yes Whether to follow symlinks when generating the precache. Defaults to true.

Runtime Caching

In addition to precaching, strategies can be provided for specific routes to determine whether and how they can be cached. This routes option is an array of objects with the following properties:

Property Type Optional Description
urlPattern string No A pattern string (which will be converted a regular expression) that matches a specific route.
strategy string No The caching strategy (see below).
options object Yes An object of additional options, each detailed below.
cacheName string Yes The name of the cache to use for the route. Note that the cachePrefix is not prepended to the cache name. Defaults to the main runtime cache (${cachePrefix}-runtime-${domain}).
cacheableResponse object Yes Uses HTTP status codes and or headers to determine whether a response can be cached. This object has two optional properties: statuses and headers. statuses is an array of HTTP status codes that should be considered valid for the cache. headers is an object of HTTP header and value pairs; at least one header must match for the response to be considered valid. Defaults to { statuses: [ 200 ] } when the strategy is 'cacheFirst', and { statuses: [0, 200] } when the strategy is either networkFirst or staleWhileRevalidate.
expiration object Yes Controls how the cache is invalidated. This object has two optional properties. maxEntries is the number of responses that can be cached at any given time. Once this max is exceeded, the oldest entry is removed. maxAgeSeconds is the oldest a cached response can be in seconds before it gets removed.
networkTimeoutSeconds number Yes Used with the networkFirst strategy to specify how long in seconds to wait for a resource to load before falling back on the cache.


Four routing strategies are currently supported:

  • networkFirst attempts to load a resource over the network, falling back on the cache if the request fails or times out. This is a useful strategy for assets that either change frequently or may change frequently (i.e., are not versioned).
  • cacheFirst loads a resource from the cache unless it does not exist, in which case it is fetched over the network. This is best for resources that change infrequently or can be cached for a long time (e.g., versioned assets).
  • networkOnly forces the resource to always be retrieved over the network, and is useful for requests that have no offline equivalent.
  • staleWhileRevalidate requests resources from both the cache and the network simulaneously. The cache is updated with each successful network response. This strategy is best for resources that do not need to be continuously up-to-date, like user avatars. However, when fetching third-party resources that do not send CORS headers, it is not possible to read the contents of the response or verify the status code. As such, it is possible that a bad response could be cached. In such cases, the networkFirst strategy may be a better fit.


import ServiceWorkerPlugin from '@dojo/webpack-contrib/service-worker-plugin/ServiceWorkerPlugin';

new ServiceWorkerPlugin({
	cachePrefix: 'my-app',

	// exclude the "admin" bundle from caching
	excludeBundles: [ 'admin' ],

	routes: [
		// Use the cache-first strategy for loading images, adding them to the "my-app-images" cache.
		// Only the first ten images should be cached, and for one week.
			urlPattern: '.*\\.(png|jpg|gif|svg)',
			strategy: 'cacheFirst',
			cacheName: 'my-app-images',
			expiration: { maxEntries: 10, maxAgeSeconds: 604800 }

		// Use the cache-first strategy to cache up to 25 articles that expire after one day.
			urlPattern: '',
			strategy: 'cacheFirst',
			expiration: { maxEntries: 25, maxAgeSeconds: 86400 }


A webpack plugin that provides a visualization of the size of webpack output with an interactive sunburst graphic. Functionally this is a copy of webpack-bundle-analyzer with a custom visualization.

The plugin accepts an options object with the following optional properties.

Property Type Description Default
analyzerMode 'server' or 'static' or 'disabled' Whether to serve bundle analysis in a live server, render the report in a static HTML file or files, or to disable visual report generation entirely. `'server'
analyzerPort number The port to use in server mode 8888
reportFilename string Path to the report bundle file. Multiple report will be created with -<bundleName> appended to this value if there is more than one output bundle. 'report.html'
openAnalyzer boolean Whether the report should be opened in a browser automatically true
generateStatsFile boolean Whether a JSON Webpack Stats file should be generated false
statsFilename string Name to use for the stats file if one is generated 'stats.json'
statsOptons any Options to pass to stats.toJson(). More documentation can be found here null
logLevel 'info' or 'warn' or 'error' or 'silent' The level of logs from this plugin 'info'


import BundleAnalyzerPlugin from '@dojo/webpack-contrib/webpack-bundle-analyzer/BundleAnalyzerPlugin';

new BundleAnalyzerPlugin({
	analyzerMode: 'static',
	reportFilename: '../info/report.html',
	openAnalyzer: false


A custom webpack plugin that conditionally loads supported dojo shims based on usage and browser capabilities.

Supported Shims

  • @dojo/framework/shim/IntersectionObserver
  • @dojo/framework/shim/ResizeObserver
  • @dojo/framework/shim/WebAnimations

To use the plugin, use the provided bootstrap.js from @dojo/webpack-contrib/bootstrap-plugin as the application entry and add the plugin to the webpack configuration.

The BootstrapPlugin accepts requires the path to application entry point and an array of shimModules to process.

new BootstrapPlugin({
	entryPath: mainEntryPath,
	shimModules: [
			module: '@dojo/framework/shim/IntersectionObserver',
			has: 'intersection-observer'
			module: '@dojo/framework/shim/ResizeObserver',
			has: 'resize-observer'
			module: '@dojo/framework/shim/WebAnimations',
			has: 'web-animations'



A custom TypeScript transformer that generates registry keys for widgets included in lazily-loaded bundles. This allows widget authors to use the same pattern for authoring widgets regardless of whether they are loaded from a registry or imported directly.

For example, if LazyWidget needs to be split into a separate bundle and this transformer is not applied, then LazyWidget would need to be added to the registry (registry.define('lazy-widget', LazyWidget)), and all calls to w(LazyWidget) would need to be updated to reference its registry key (w<LazyWidget>('lazy-widget')). By using this transformer, LazyWidget would instead be added to the registry at build time, allowing existing code to remain unchanged.

How do I contribute?

We appreciate your interest! Please see the Dojo 2 Meta Repository for the Contributing Guidelines.

Code Style

This repository uses prettier for code styling rules and formatting. A pre-commit hook is installed automatically and configured to run prettier against all staged files as per the configuration in the projects package.json.

An additional npm script to run prettier (with write set to true) against all src and test project files is available by running:

npm run prettier


To test this package, after ensuring all dependencies are installed, run the following command:

$ grunt test

Licensing information

© 2018 JS Foundation. New BSD license.