#Deprecated options

This page lists configuration options that have been deprecated in Rspack.

These options are kept for backward compatibility only and should not be used in new projects.

#experiments.topLevelAwait

• Type: boolean
• Default: true

Enables support for Top-level await. Top-level await can only be used in modules with ModuleType set to javascript/esm.

Enabled by default. Can be disabled with this configuration:

export default {
  experiments: {
    topLevelAwait: false,
  },
};

#experiments.lazyCompilation

Used to enable lazy compilation.

#experiments.layers

• Type: boolean
• Default: true

Controls whether to enable the layer feature. Layers add an identifier prefix to all modules in a subgraph starting from a module in the module graph, to distinguish them from modules in different layers. For example:

The layer of the index.js module is null by default, and its identifier is ./index.js. If we set layer = 'client' for it, its identifier becomes (client)/./index.js. At this point, the index.js modules in these two different layers are treated as distinct modules, because their unique identifiers differ. The final output includes the artifacts of both modules.

By default, a module's layer is null, and it inherits its parent module's layer. You can add a layer to an entry module using entryOptions.layer, and add a layer to matched modules using module.rule[].layer. Additionally, you can match based on the parent module's layer using module.rule[].issuerLayer.

export default {
  experiments: {
    layers: true,
  },
};

#experiments.parallelCodeSplitting

• Type: boolean
• Default: false

Enabling this configuration will activate a new multi-threaded code splitting algorithm. If your project includes many dynamic imports and doesn't have cyclic chunks, this can greatly reduce the time spent on the code splitting process.

export default {
  experiments: {
    parallelCodeSplitting: true,
  },
  optimization: {
    removeAvailableModules: true,
  },
};

#rules[].loaders

An array to pass the loader package name and its options.

#experiments.inlineConst

• Type: boolean
• Default: false

Used to enable the experimental feature for cross-module inline optimization for constant exports.

#experiments.inlineEnum

• Type: boolean
• Default: false

Used to enable inline optimization for TypeScript enums.

#experiments.lazyBarrel

• Type: boolean
• Default: true

Used to enable lazy barrel optimization for skipping the building of unused re-export modules in side-effect-free barrel files.

#experiments.typeReexportsPresence

• Type: boolean
• Default: false

Used to enable error tolerance for type re-exports.

#module.parser.javascript.inlineConst

• Type: boolean
• Default: false

Used to control whether to perform cross-module inline optimization for constant exports in the parser.