My Visual Studio Code extension uses the node module highlight.js which comes with a folder full of CSS files. These provide colour schemes for syntax colouring. It has become necessary to bundle some of the CSS files.

It's about bundling an asset

The objective is to bundle a CSS file and at run-time access the file content as a string. If that can be achieved without an import statement that would be perfect. Normally, how exactly one accesses the content of the bundled file would be a separate question, but I have a feeling that content retrieval and how one should go about bundling the asset are closely entwined.

I freely admit to having a weak understanding of WebPack.

The story so far

The bundler is specified in package.json as "webpack": "^5.4.0" but I don't know how to ascertain what is actually present. It is conceivable that there is something wrong with my setup: when I try to run webpack --version on a command prompt in the project folder, it responds

CLI for webpack must be installed.
  webpack-cli (https://github.com/webpack/webpack-cli)

We will use "npm" to install the CLI via "npm install -D webpack-cli".
Do you want to install 'webpack-cli' (yes/no):

The first time this happened I responded yes. After a flurry of installation and another try the same thing happened. However, vsce package has no trouble using webpack for a production build and pressing F5 to debug successfully puts together a development build in a dist folder with an unminified file I can examine (which is how I know the file mentioned below is being bundled).

Moving on from there I've modified webpack.config.js like so

//@ts-check

'use strict';

const path = require('path');

/**@type {import('webpack').Configuration}*/
const config = {
  target: 'node', // vscode extensions run in a Node.js-context -> https://webpack.js.org/configuration/node/

  entry: './src/extension.ts', // the entry point of this extension, -> https://webpack.js.org/configuration/entry-context/
  output: {
    // the bundle is stored in the 'dist' folder (check package.json), -> https://webpack.js.org/configuration/output/
    path: path.resolve(__dirname, 'dist'),
    filename: 'extension.js',
    libraryTarget: 'commonjs2',
    devtoolModuleFilenameTemplate: '../[resource-path]'
  },
  devtool: 'source-map',
  externals: {
    vscode: 'commonjs vscode' // the vscode-module is created on-the-fly and must be excluded. Add other modules that cannot be webpack'ed, -> https://webpack.js.org/configuration/externals/
  },
  resolve: {
    // support reading TypeScript and JavaScript files, -> https://github.com/TypeStrong/ts-loader
    extensions: ['.ts', '.js', '.css']
  },
  module: {
    rules: [
      {
        test: /\.ts$/,
        exclude: /node_modules/,
        use: [
          {
            loader: 'ts-loader'
          }
        ]
      },
      {
        test: /\.css$/,
        use: [
          'style-loader',
          'css-loader'
        ]
      }
    ]
  }
};
module.exports = config;

As you can see there are rules and loaders for CSS.

When I add this import

import "../node_modules/highlight.js/styles/atelier-dune-light.css";

webpack happily builds the bundle and when I inspect it I can find the bundled CSS.

However, when I try to load the extension in the extension debug host, it fails to load, with this message.

Activating extension 'pdconsec.vscode-print' failed: document is not defined.

Enabling break on caught exceptions reveals this rather surprising exception.

Exception has occurred: Error: Cannot find module 'supports-color'
Require stack:
- c:\Users\Peter\AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules.asar\get-uri\node_modules\debug\src\node.js
- c:\Users\Peter\AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules.asar\get-uri\node_modules\debug\src\index.js
- c:\Users\Peter\AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules.asar\get-uri\dist\index.js
- c:\Users\Peter\AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules.asar\vscode-proxy-agent\out\agent.js
- c:\Users\Peter\AppData\Local\Programs\Microsoft VS Code\resources\app\node_modules.asar\vscode-proxy-agent\out\index.js
- c:\Users\Peter\AppData\Local\Programs\Microsoft VS Code\resources\app\out\bootstrap-amd.js
- c:\Users\Peter\AppData\Local\Programs\Microsoft VS Code\resources\app\out\bootstrap-fork.js

OK, so activation failed because the loader barfed. But WTF does importing CSS have to do with support-color?

Remove the import and it runs just fine. I really don't know how to respond to this; it's not clear to me why a demand for a stylesheet should cause that error. At this point I look to others for guidance and advice.