eslint-rspack-plugin Migration Guide (v4 -> v5)

This guide covers breaking changes you need to handle when upgrading eslint-rspack-plugin from v4 to v5.

Breaking Changes

Drop ESLint 8 Support

ESLint 8 is no longer supported in v5.

The supported ESLint peer dependency range is now ^9.0.0 || ^10.0.0.

Drop Node 18 Support

Node.js 18 is no longer supported in v5.

The minimum supported Node.js version is now >=20.19.0.

Native ESM Package

eslint-rspack-plugin is now published as a native ES module package. Use ESM syntax when importing it from your Rspack config:

- const ESLintPlugin = require('eslint-rspack-plugin');
+ import ESLintPlugin from 'eslint-rspack-plugin';

export default {
  plugins: [new ESLintPlugin()],
};

If your Rspack config is still CommonJS, migrate it to ESM first by using export default and either a .mjs config file or a .js config file in a package with "type": "module".

Flat Config is the Default

In v4, eslint-rspack-plugin used eslintrc by default for ESLint 8 and ESLint 9. In v5, the default configType is flat.

If your project already uses eslint.config.js, you can usually remove any explicit configType: 'flat' option:

import ESLintPlugin from 'eslint-rspack-plugin';

export default {
  plugins: [
    new ESLintPlugin({
-     configType: 'flat',
    }),
  ],
};

If your project still uses .eslintrc, either migrate to flat config or explicitly keep legacy config mode:

import ESLintPlugin from 'eslint-rspack-plugin';

export default {
  plugins: [
    new ESLintPlugin({
+     configType: 'eslintrc',
    }),
  ],
};

eslintrc is deprecated by ESLint, so flat config is the recommended migration target.

Remove threads

The plugin-specific threads option was removed in v5. The plugin no longer creates its own worker pool, and there is no replacement plugin option.

If you use ESLint 9.34.0 or later and still want parallel linting, pass ESLint's native concurrency Node.js API option through the plugin options:

import ESLintPlugin from 'eslint-rspack-plugin';

export default {
  plugins: [
    new ESLintPlugin({
-     threads: true,
+     concurrency: 'auto',
    }),
  ],
};

Use a number for an explicit worker count. If you use ESLint 9.0-9.33, or if you previously used threads: false, remove the threads option instead. ESLint's default concurrency value is 'off'.

When you enable concurrency, ESLint options must support structured cloning. If you pass functions or complex plugin objects through ESLint options, leave concurrency off or move that configuration into your ESLint config file.

severity Replaces Emit and Fail Options

The emitError, emitWarning, failOnError, failOnWarning, and quiet options were removed. Use the new severity option to choose how ESLint diagnostics are emitted to Rspack.

By default, ESLint errors are emitted as Rspack errors and ESLint warnings are emitted as Rspack warnings:

new ESLintPlugin({
  severity: {
    error: 'error',
    warning: 'warning',
  },
});

emitError: false

Use severity.error: 'off' to hide ESLint errors:

// v4
new ESLintPlugin({ emitError: false });

// v5
new ESLintPlugin({ severity: { error: 'off' } });

emitWarning: false

Use severity.warning: 'off' to hide ESLint warnings:

// v4
new ESLintPlugin({ emitWarning: false });

// v5
new ESLintPlugin({ severity: { warning: 'off' } });

quiet: true

Use severity.warning: 'off' to keep ESLint errors and hide ESLint warnings:

// v4
new ESLintPlugin({ quiet: true });

// v5
new ESLintPlugin({ severity: { warning: 'off' } });

failOnWarning: true

Use severity.warning: 'error' to emit ESLint warnings as Rspack errors:

// v4
new ESLintPlugin({ failOnWarning: true });

// v5
new ESLintPlugin({ severity: { warning: 'error' } });

failOnError

There is no direct failOnError replacement. ESLint errors are emitted as Rspack errors by default, so they fail production builds without an extra plugin option.

If you want to keep ESLint error output visible without failing the build, emit ESLint errors as Rspack warnings instead:

new ESLintPlugin({
  severity: {
    error: 'warning',
  },
});