watch

• Type: false | object with the properties below
• Optional
• Experimental

Defined in: options/input-options.ts:724

Watch mode related options.

These options only take effect when running with the --watch flag, or using watch() API.

Rolldown uses the following APIs to watch for changes by default:

• Linux, Android: inotify
• macOS: FSEvents
• Windows: ReadDirectoryChangesW
• BSD descendants (e.g. FreeBSD): kqueue
• Other: None (polling)

There are some limitations for each API. If you need to work around them, you can use watcher.usePolling to force Rolldown to use polling instead of the native API.

Using on Windows Subsystem for Linux (WSL) 2

When running Rolldown on WSL2, file system watching does not work when a file is edited by Windows applications (non-WSL2 process). This is due to a WSL2 limitation. This also applies to running on Docker with a WSL2 backend.

To fix it, you could either:

• Recommended: Use WSL2 applications to edit your files.
  • It is also recommended to move the project folder outside of a Windows filesystem. Accessing Windows filesystem from WSL2 is slow. Removing that overhead will improve performance.
• Set usePolling: true.
  • Note that usePolling leads to higher CPU utilization.

buildDelay?

• Type: number
• Optional

Defined in: options/input-options.ts:127

Configures how long Rolldown will wait for further changes until it triggers a rebuild in milliseconds.

Even if this value is set to 0, there's a small debounce timeout configured in the file system watcher. Setting this to a value greater than 0 will mean that Rolldown will only trigger a rebuild if there was no change for the configured number of milliseconds. If several configurations are watched, Rolldown will use the largest configured build delay.

This option is useful if you use a tool that regenerates multiple source files very slowly. Rebuilding immediately after the first change could cause Rolldown to generate a broken intermediate build before generating a successful final build, which can be confusing and distracting.

Default

0

clearScreen?

• Type: boolean
• Optional

Defined in: options/input-options.ts:188

Whether to clear the screen when a rebuild is triggered.

Default

true

exclude?

• Type: string | RegExp | (string | RegExp)[]
• Optional

Defined in: options/input-options.ts:169

Filter to prevent files from being watched.

Strings are treated as glob patterns.

Example

export default defineConfig({
  watch: {
    exclude: 'node_modules/**',
  },
})

Default

[]

include?

• Type: string | RegExp | (string | RegExp)[]
• Optional

Defined in: options/input-options.ts:153

Filter to limit the file-watching to certain files.

Strings are treated as glob patterns. Note that this only filters the module graph but does not allow adding additional watch files.

Example

export default defineConfig({
  watch: {
    include: 'src/**',
  },
})

Default

[]

notify?

• Type: WatcherFileWatcherOptions
• Optional

Defined in: options/input-options.ts:135

Deprecated

Use watcher instead.

onInvalidate()?

• Type: (id) => void
• Optional

Defined in: options/input-options.ts:183

An optional function that will be called immediately every time a module changes that is part of the build.

This is different from the watchChange plugin hook, which is only called once the running build has finished. This may for instance be used to prevent additional steps from being performed if we know another build will be started anyway once the current build finished. This callback may be called multiple times per build as it tracks every change.

Parameters

id

string

The id of the changed module.

Returns

void

skipWrite?

• Type: boolean
• Optional

Defined in: options/input-options.ts:109

Whether to skip the bundle.write() step when a rebuild is triggered.

Default

false

watcher?

• Type: WatcherFileWatcherOptions
• Optional

Defined in: options/input-options.ts:131

File watcher options for configuring how file changes are detected.