#tools.swc

• Type:

type ToolsSwc =
  | Rspack.SwcLoaderOptions
  | ((config: Rspack.SwcLoaderOptions) => Rspack.SwcLoaderOptions | undefined);

• Default:

const defaultOptions = {
  jsc: {
    externalHelpers: true,
    parser: {
      tsx: false,
      syntax: 'typescript',
      decorators: true,
    },
  },
  experimental: {
    cacheRoot: './node_modules/.cache/.swc',
    keepImportAttributes: true,
  },
  isModule: 'unknown',
  env: {
    // Read the browserslist configuration of the project
    targets: browserslist,
  },
  // ...some other conditional options
};

You can set the options of builtin:swc-loader through tools.swc.

Refer to Configure SWC for more details.

#Object type

tools.swc can be configured as an object, this object will be deeply merged with the built-in builtin:swc-loader option.

export default {
  tools: {
    swc: {
      jsc: {
        externalHelpers: false,
      },
    },
  },
};

#Function type

tools.swc can also be configured as a function, this function takes one argument, which is the built-in builtin:swc-loader option. You can modify this object then return a new config. For example:

export default {
  tools: {
    swc: (config) => {
      config.jsc ||= {};
      config.jsc.externalHelpers = false;
      return config;
    },
  },
};

#Configuration conflicts

In the SWC configuration, jsc.target (which specifies the ECMAScript version, such as es2015) and env cannot coexist.

To avoid conflicts, Rsbuild adopts the following handling strategies:

• If Rsbuild detects that you have manually set jsc.target in tools.swc, it will automatically remove the built-in env.targets.
• If output.polyfill is configured, Rsbuild will force set env.mode. In this case, you cannot use jsc.target.