webpack-target-webextension

This webpack 5 plugin (works on rspack!) provides reasonable presets and fixes things that don't work for a Web Extension.

If you are looking for webpack 4 support, please install 0.2.1. Document for 0.2.1.

The list of things we fixed in this plugin:

• Code splitting (chunk loader)
• Hot Module Reload
• Public path

A quick guide

If you are familiar with WebExtension and webpack, this is a quick guide on how to configure this plugin and your manifest.json.

webpack.config.js

1module.exports = {
2    context: __dirname,
3    entry: {
4        background: join(__dirname, './src/background/index.js'),
5        content: join(__dirname, './src/content-script/index.js'),
6        options: join(__dirname, './src/options-page/index.js'),
7    },
8    output: {
9        path: join(__dirname, './dist'),
10    },
11    plugins: [
12        new HtmlPlugin({ filename: 'options.html', chunks: ['options'] }),
13        new WebExtension({
14            background: { pageEntry: 'background' },
15        }),
16        new CopyPlugin({
17            patterns: [{ from: 'manifest.json' }],
18        }),
19    ],
20}

manifest.json

1{
2  "manifest_version": 3,
3  "name": "Your extension",
4  "version": "1.0.0",
5  "background": {
6    "service_worker": "./background.js"
7 },
8  // ⚠ Those files can be accessed by normal websites too.
9  "web_accessible_resources": [
10 {
11      "resources": ["/*.js"],
12      "matches": ["<all_urls>"]
13 },
14    // only needed for development (hot module reload)
15 {
16      "resources": ["/hot/*.js", "/hot/*.json"],
17      "matches": ["<all_urls>"]
18 }
19 ],
20  "content_scripts": [
21 {
22      "matches": ["<all_urls>"],
23      "js": ["./content.js"]
24 }
25 ],
26  "permissions": ["scripting"],
27  "host_permissions": ["<all_urls>"],
28  "options_ui": {
29    "page": "options.html",
30    "open_in_tab": true
31 }
32}

You can also refer to ./examples/react-hmr which is a working project.

How to configure

Code splitting

Content script

To load an async chunk in content scripts, you need to configure the chunk loader.

(default) dynamic import()

Compatibility: at least Firefox 89 and Chrome 63.

To disable this loader, you can set output.environment.dynamicImport to false.

You MUST add your JS files to web_accessible_resources in the manifest.json, otherwise the import() call will fail.

[!WARNING] Adding files to web_accessible_resources allows normal websites to fetch them.

---

chrome.tabs.executeScript (Manifest V2 only)

This method requires options.background.pageEntry to be configured and options.background.classicLoader is not false (it defaults to true).

---

chrome.scripting.executeScript (Manifest V3 only)

• This method will fall back to chrome.tabs.executeScript when there is no chrome.scripting.
• This method requires "scripting" permission in the manifest.json.
• This method requires options.background to be configured.
• This method requires options.background.classicLoader is not false (defaults to true).

Main world content script

You must configure the content script by dynamic import(). You also need to set output.publicPath manually (like chrome-extension://jknoiechepeohmcaoeehjaecapdplcia/, the full URL is necessary).

Background worker (Manifest V3)

[!WARNING] This plugin does not work with "background.type" in manifest.json set to "module" (native ES Module service worker). Tracking issue: #24

Code splitting is supported for background service workers, but it will load all chunks initially. See https://bugs.chromium.org/p/chromium/issues/detail?id=1198822.

To turn off this fix, set options.background.eagerChunkLoading to false. If you turn off this fix, loading an async chunk will be a runtime error.

Hot Module Reload

[!WARNING] It's not possible to support HMR for Manifest V3 background workers.

You will see

"[HMR] Update check failed: NetworkError: Failed to execute 'importScripts' on 'WorkerGlobalScope': The script at 'chrome-extension://...' failed to load."

See https://bugs.chromium.org/p/chromium/issues/detail?id=1198822

[!WARNING] The HMR WebSocket server might be blocked by the Content Security Policy, which prevents the reset of the code from being executed. Please disable HMR if you experience this problem.

This plugin fixes Hot Module Reload and provides reasonable defaults for DevServer. Please set devServer.hot to false to disable HMR support.

To disable this fix, set options.hmrConfig to false.

You need to add *.json to your web_accessible_resources to make HMR work.

Example: Draw UI in the content scripts with React and get React HRM. ./examples/react-hmr

Source map

[!WARNING] No eval based source map is available in Manifest v3.

[!WARNING] DO NOT add unsafe-eval to your CSP in production mode!

To use source maps based on eval, you must use Manifest v2 and have script-src 'self' 'unsafe-eval'; in your CSP (content security policy).

Public path

This plugin fixes the public path whether the output.path is set or not.

Options

options.background

Example:

1new WebExtensionPlugin({
2  background: { pageEntry: 'background', serviceWorkerEntry: 'background-worker' },
3})

1export interface BackgroundOptions {
2  noDynamicEntryWarning?: boolean
3  /**
4   * The entry point of the background page.
5   */
6  pageEntry?: string
7  /**
8   * The entry point of the service worker.
9   */
10  serviceWorkerEntry?: string
11  /**
12   * Only affects Manifest V3.
13   *
14   * Load all chunks at the beginning
15   * to workaround the Chrome bug
16   * https://bugs.chromium.org/p/chromium/issues/detail?id=1198822.
17   *
18   * NOT working for rspack.
19   *
20   * @defaultValue true
21   */
22  eagerChunkLoading?: boolean
23  /**
24   * Add the support code that uses
25   * `chrome.scripting.executeScript` (MV3) or
26   * `chrome.tabs.executeScript` (MV2) when
27   * dynamic import does not work for chunk loading
28   * in the content script.
29   * @defaultValue true
30   */
31  classicLoader?: boolean
32  /**
33   * Add a try-catch wrapper around the entry file of serviceWorkerEntry
34   * so if the initial code throws, you can still open the console of it.
35   *
36   * Does not work in rspack.
37   *
38   * @defaultValue true
39   */
40  tryCatchWrapper?: boolean
41}

options.hmrConfig

Default value: true

This option provides reasonable defaults for HMR and DevServer.

options.weakRuntimeCheck

If you experienced a compatibility issue with any of the following plugins, please this option:

• mini-css-extract-plugin
• HtmlWebpackPlugin

options.experimental_output

This is an experimental API. API might change at any time. Please provide feedback!

TLDR: How to use this

string

If you don't strictly rely on run_at, set it as the following

1export default {
2  entry: {
3    myContentScript: 'src/contentScript.ts',
4  },
5  // ...
6  plugins: [
7    // ...
8    new WebExtensionPlugin({
9      // ...
10      experimental_output: {
11        myContentScript: 'cs.js'
12      },
13    })
14  ]
15}

1{
2  // ...
3  "content_scripts": [
4    {
5      "matches": ["..."],
6      "js": ["cs.js"]
7    }
8  ]
9}

function

If you cannot use asynchronous loading, set up like below. This setup requires you to have a manifest.json being emitted.

1export default {
2  entry: {
3    myContentScript: 'src/contentScript.ts',
4  },
5  // ...
6  plugins: [
7    // ...
8    new WebExtensionPlugin({
9      // ...
10      experimental_output: {
11        myContentScript: (manifest, list) => {
12          manifest.content_scripts[0].js = list
13        }
14      },
15    })
16  ]
17}

object

1export default {
2  entry: {
3    background: 'src/background.ts',
4  },
5  // ...
6  plugins: [
7    // ...
8    new WebExtensionPlugin({
9      // ...
10      experimental_output: {
11        background: {
12          file: 'sw.js',
13          touch(manifest, file) {
14            manifest.background.service_worker = file
15          }
16        },
17      },
18    })
19  ]
20}

Explanation

This is an experimental API. API might change at any time. Please provide feedback!

This option helps the initial chunk loading of content scripts/the background service worker, usually needed when optimization.runtimeChunk or optimization.splitChunks.chunks is used.

This option accepts an object, where the keys are the entry name, and the value is described below.

This option replaces the HTMLWebpackPlugin where the background service worker and content scripts do not use HTML to load files.

If the value is a string (an output file name), for content scripts, it creates an extra entry file to load all initial chunks asynchronously via dynamic import. This asynchronous loading behavior is limited to the platform limit and breaks run_at.

If the value is a string (an output file name), for the background service worker (specified via options.background.serviceWorkerEntry), it creates an extra entry file to load all initial chunks synchronously.

The file name specified MUST NOT be any existing file.

If the value is a function ((manifest: any, chunks: string[]) => void), it requires a "manifest.json" in the emitted files and lets you edit it on the fly to include all the initial chunks. This option does not apply to the background service worker because manifest.json does not accept multiple files.

If the value is an object ({ file: string; touch(manifest: any, file: string): void }), it generates a new file (see the behavior of string above) and provides a callback to edit the manifest.json (see the behavior of function above).

If the value is false, it asserts that this entry does not have more than one initial file, otherwise, it will be a compile error.

If the value is undefined, it silences the warning for the background service worker.

You can also change your configuration to avoid optimization.runtimeChunk or optimization.splitChunks.chunks, in this case, webpack only generates 1 initial file so you don't need this option.

Rspack support

Rspack support is provided as a best effort, please open an issue if you have encountered any problems.

Here are known issues:

• experimental_output is necessary for chunk splitting.