rollup-plugin-web-worker-loader

rollup-plugin-web-worker-loader

Rollup plugin to handle Web Workers.

Can inline the worker code or emit a script file using code-splitting. Handles Worker dependencies and can emit source maps. Worker dependencies are added to Rollup's watch list. Supports bundling workers for Node.js environments

Getting started

yarn add rollup-plugin-web-worker-loader --dev

Add the plugin to your rollup configuration:

import webWorkerLoader from 'rollup-plugin-web-worker-loader';

export default {
    entry: 'src/index.js',
    plugins: [
        webWorkerLoader(/* configuration */),
    ],
    format: 'esm',
};

Bundle the worker code using the RegEx pattern specified in the plugin's configuration. By default you can add the prefix web-worker: to your imports:

// here we use the default pattern but any RegEx can be configured
import DataWorker from 'web-worker:./DataWorker';

const dataWorker = new DataWorker();
dataWorker.postMessage('Hello World!');

Configuration

The plugin responds to the following configuration options:

webWorkerLoader({
    targetPlatform?: string,        // The platform workers should be built for, can be 'auto', 'browser', 'node' or 'base64'.
                                    // specifying a target platform other than 'auto' reduces the amount of loader code.
                                    // The `base64` options forces inline and the import results on a base64 string that
                                    // encodes the worker's source code. NOTE: The string does not include a mime type.
                                    // 'auto' detectes the target platform and selects between 'browser` and 'node'.
                                    // Default: 'auto'

    pattern?: RegEx,                // A RegEx instance describing the pattern that matches the files to import as
                                    // web workers. If capturing groups are present, the plugin uses the contents of the
                                    // last capturing group as the path to the worker script. Default: /web-worker:(.+)/
    
    extensions?: string[],          // An array of strings to use as extensions when resolving worker files.
                                    // Default: ['.js']


    sourcemap?: boolean,            // When inlined, should a source map be included in the final output. Default: false

    inline?: boolean,               // Should the worker code be inlined (Base64). Default: true

    forceInline?: boolean,          // *EXPERIMENTAL* when inlined, forces the code to be included every time it is imported
                                    // useful when using code splitting: Default: false

    external?: string[],            // *EXPERIMENTAL* override rollup resolution of external module IDs
                                    // useful to inline external dependencies in a worker blob. Default: undefined

    preserveSource?: boolean,       // When inlined and this option is enabled, the full source code is included in the
                                    // built file, otherwise it's embedded as a base64 string. Default: false
    
    preserveFileNames?: boolean,    // When code splitting is used (`inline === false`) the input worker file names are
                                    // preserved, if duplicates are found `-n` is appended to the file names.
                                    // Default: false

    enableUnicodeSupport?: boolean, // When inlined in Base64 format, this option enables unicode support (UTF16). This
                                    // flag is disabled by default because supporting UTF16 doubles the size of the final
                                    // payload. Default: false

    outputFolder?: string,          // When code splitting is used (`inline: false`), folder in which the worker scripts
                                    // should be written to. Default: '' (same as build output folder)

    loadPath?: string,              // This option is useful when the worker scripts need to be loaded from another folder.
                                    // Default: ''

    plugins?: Array,                // An array of extra plugins to use while compiling the worker code. Used to apply 
                                    // transformations to the worker code and not the main code (i.e. minify)
                                    // NOTE: these plugins be added to the rollop process on top of the plugins in the
                                    // default configuration.
                                    // Default: []
    
    skipPlugins?: Array,            // Plugin names to skip for web worker build
                                    // Default: [ 'liveServer', 'serve', 'livereload' ]
})

TypeScript

An example project that uses this plugin with TypeScript can be found here

Notes

WARNING: To use code-splitting for the worker scripts, Rollup v1.9.2 or higher is required. See https://github.com/rollup/rollup/issues/2801 for more details.

The sourcemap configuration option is ignored when inline is set to false, in that case the project's sourcemap configuration is inherited.

loadPath is meant to be used in situations where code-splitting is used (inline = false) and the entry script is hosted in a different folder than the worker code.

Setting targetPlatform to 'base64' will ignore the inline option and will always inline the resulting code.

Roadmap

• Bundle file as web worker blob
• Support for dependencies using import
• Include source map
• Configuration options to inline or code-split workers
• Provide capability checks and fallbacks DROPPED (all modern environments support workers)
• Avoid code duplication DROPPED (there are better solutions for this purpose)