source-map-loader

Extracts source maps from existing source files (from their <code>sourceMappingURL</code>).

Getting Started

To begin, you'll need to install source-map-loader:

npm i -D source-map-loader

or

yarn add -D source-map-loader

or

pnpm add -D source-map-loader

Then add the loader to your webpack configuration. For example:

file.js

import css from "file.css";

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        enforce: "pre",
        use: ["source-map-loader"],
      },
    ],
  },
};

The source-map-loader extracts existing source maps from all JavaScript entries. This includes both inline source maps as well as those linked via a sourceMappingURL.

All source map data is passed to webpack for processing as per a chosen source map style specified by the devtool option in webpack.config.js.

This loader is especially useful when using third-party libraries having their own source maps. If not extracted and processed into the source map of the webpack bundle, browsers may misinterpret or ignore source map data.

The source-map-loader allows webpack to maintain source map data continuity across libraries so ease of debugging is preserved.

The source-map-loader will extract from any JavaScript file, including those in the node_modules directory.

Be mindful in setting include and exclude rule conditions to maximize bundling performance.

Finally, run webpack using the method you normally use (e.g., via CLI or an npm script).

Options

filterSourceMappingUrl

Type: Function Default: undefined

Allows you to specify the behavior of the loader for SourceMappingURL comment.

The function must return one of the following values:

• true or 'consume' - consume the source map and remove SourceMappingURL comment (default behavior)
• false or 'remove' - do not consume the source map and remove SourceMappingURL comment
• skip - do not consume the source map and do not remove SourceMappingURL comment

Example configuration:

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        enforce: "pre",
        use: [
          {
            loader: "source-map-loader",
            options: {
              filterSourceMappingUrl: (url, resourcePath) => {
                if (/broker-source-map-url\.js$/i.test(url)) {
                  return false;
                }
                if (/keep-source-mapping-url\.js$/i.test(resourcePath)) {
                  return "skip";
                }
                return true;
              },
            },
          },
        ],
      },
    ],
  },
};

Examples

Ignoring Warnings

To ignore warnings, you can use the following configuration:

webpack.config.js

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        enforce: "pre",
        use: ["source-map-loader"],
      },
    ],
  },
  ignoreWarnings: [/Failed to parse source map/],
};

More information about the ignoreWarnings option can be found here

Contributing

We welcome all contributions! If you're new here, please take a moment to review our contributing guidelines before submitting issues or pull requests.

CONTRIBUTING

License

MIT