#Watch

Rspack can watch files and recompile whenever they change.

#watch

• Type: boolean
• Default: false

Turn on watch mode. This means that after the initial build, Rspack will continue to watch for changes in any of the resolved files.

export default {
  // ...
  watch: true,
};

#watchOptions

• Type: object

A set of options used to customize watch mode.

export default {
  // ...
  watchOptions: {
    ignored: /node_modules/,
    poll: true,
  },
};

#watchOptions.aggregateTimeout

• Type: number
• Default: 5

Add a delay before rebuilding once the first file changed. This allows Rspack to aggregate any other changes made during this time period into one rebuild. Pass a value in milliseconds:

export default {
  //...
  watchOptions: {
    aggregateTimeout: 600,
  },
};

#watchOptions.ignored

• Type: RegExp | string | string[]
• Default: /[\\/](?:\.git|node_modules)[\\/]/

The path that matches is excluded while watching. Watching many files can result in a lot of CPU or memory usage.

Since Rspack v1.2.0, node_modules and .git directories are excluded by default. This means that changes to files in these directories will not trigger a rebuild.

If you want to watch the node_modules directory, you can set it to only exclude the .git directory:

export default {
  //...
  watchOptions: {
    ignored: /\.git/,
  },
};

ignored can use glob matching:

export default {
  //...
  watchOptions: {
    ignored: '**/.git',
  },
};

It is also possible to use multiple glob patterns:

export default {
  //...
  watchOptions: {
    ignored: ['**/files/**/*.js', '**/.git', '**/node_modules'],
  },
};

In addition, you can specify one or more absolute paths:

import path from 'node:path';

export default {
  //...
  watchOptions: {
    ignored: [path.posix.resolve(__dirname, './ignored-dir')],
  },
};

When using glob patterns, Rspack convert them to regular expressions with glob-to-regexp, so make sure to get yourself familiar with it before you use glob patterns for watchOptions.ignored.

#watchOptions.poll

• Type: boolean, number
• Default: false

Whether to watch by polling.

When set to true, the default polling interval is 5007 milliseconds.

export default {
  //...
  watchOptions: {
    poll: true,
  },
};

It can also set a custom polling interval:

export default {
  //...
  watchOptions: {
    poll: 1000, // Check for changes every second
  },
};

#watchOptions.followSymlinks

• Type: boolean
• Default: false

Follow symbolic links while looking for a file. This is usually not needed as Rspack already resolves symlinks with resolve.symlinks.

export default {
  //...
  watchOptions: {
    followSymlinks: true,
  },
};

#watchOptions.stdin

• Type: boolean

Stop watching when stdin stream has ended.

export default {
  //...
  watchOptions: {
    stdin: true,
  },
};