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      • CC 4.0 License

      The content of this section is derived from the content of the following links and is subject to the CC BY 4.0 license.

      The following contents can be assumed to be the result of modifications and deletions based on the original contents if not specifically stated.

      Extends

      Used to extend configurations from other files or packages. This allows you to create a base configuration and extend it for different environments or use cases.

      • Type: string | string[]
      • Default: undefined
      Info

      This option is only supported in @rspack/cli.

      If you are using the JavaScript API or other Rspack-based tools, extends will not take effect, use webpack-merge instead.

      Basic usage

      You can extend a configuration from another file by specifying the path to the file in the extends property. The path can be absolute or relative to the configuration file:

      ESM
      CJS
      rspack.config.mjs
      export default {
  extends: './base.rspack.config.mjs',
  // Override or add to the base configuration
  output: {
    filename: '[name].bundle.js',
  },
};
      Tip

      When using relative paths, they are resolved relative to the configuration file that contains the extends property.

      Multiple configurations

      • Type: string[]
      • Default: undefined

      You can extend multiple configurations by providing an array of paths. Configurations are merged from right to left, meaning that the rightmost configuration will be merged into the leftmost one, and so on:

      rspack.config.mjs
      export default {
  extends: ['./base.rspack.config.mjs', './dev.rspack.config.mjs'],
  // Additional configuration options
  plugins: [
    // Add more plugins
  ],
};
      Merge Behavior

      When merging configurations:

      • Simple values are overwritten
      • Arrays are concatenated
      • Objects are deeply merged

      Node modules

      • Type: string
      • Default: undefined

      You can also extend configurations from packages installed in your node_modules. The package should export a valid Rspack configuration:

      rspack.config.mjs
      export default {
  extends: 'some-rspack-config-package',
  // Override or add to the package's configuration
};

      Nested extends

      Configurations can have their own extends property, allowing for nested configuration inheritance. The resolution is performed recursively:

      base.rspack.config.mjs
      export default {
  extends: './core.rspack.config.mjs',
  // Base configuration options
};
      rspack.config.mjs
      export default {
  extends: './base.rspack.config.mjs',
  // Environment-specific configuration options
};