nextjs

Fixing Next.js Error: Invalid next.config.js Options Detected

Max Rohde

Jan 6, 2023 — 4 min read

I have recently upgraded the Next.js and Next.js + Bootstrap Goldstack templates to Next.js 13.

After following the upgrade instructions, I encountered encountered a few errors that I document here along with the solutions that I found.

Error: The root value has an unexpected property

The first error I encountered was: Invalid next.config.js detected - The root value has an unexpected property:

Here the full text of the error message:

warn  - Invalid next.config.js options detected: 
  - The root value has an unexpected property, webpackDevMiddleware, which is not in the list of allowed properties (amp, analyticsId, assetPrefix, basePath, cleanDistDir, compiler, compress, crossOrigin, devIndicators, distDir, env, 
eslint, excludeDefaultMomentLocales, experimental, exportPathMap, generateBuildId, generateEtags, headers, httpAgentOptions, i18n, images, modularizeImports, onDemandEntries, optimizeFonts, output, outputFileTracing, pageExtensions, poweredByHeader, productionBrowserSourceMaps, publicRuntimeConfig, reactStrictMode, redirects, rewrites, sassOptions, 
serverRuntimeConfig, skipMiddlewareUrlNormalize, skipTrailingSlashRedirect, staticPageGenerationTimeout, swcMinify, trailingSlash, transpilePackages, typescript, useFileSystemPublicRoutes, webpack).
  - The root value has an unexpected property, configOrigin, which is not in the list of allowed properties (amp, analyticsId, assetPrefix, basePath, cleanDistDir, compiler, compress, crossOrigin, devIndicators, distDir, env, eslint, 
excludeDefaultMomentLocales, experimental, exportPathMap, generateBuildId, generateEtags, headers, httpAgentOptions, 
i18n, images, modularizeImports, onDemandEntries, optimizeFonts, output, outputFileTracing, pageExtensions, poweredByHeader, productionBrowserSourceMaps, publicRuntimeConfig, reactStrictMode, redirects, rewrites, sassOptions, serverRuntimeConfig, skipMiddlewareUrlNormalize, skipTrailingSlashRedirect, staticPageGenerationTimeout, swcMinify, trailingSlash, transpilePackages, typescript, useFileSystemPublicRoutes, webpack).
  - The root value has an unexpected property, target, which is not in the list of allowed properties (amp, analyticsId, assetPrefix, basePath, cleanDistDir, compiler, compress, crossOrigin, devIndicators, distDir, env, eslint, excludeDefaultMomentLocales, experimental, exportPathMap, generateBuildId, generateEtags, headers, httpAgentOptions, i18n, 
images, modularizeImports, onDemandEntries, optimizeFonts, output, outputFileTracing, pageExtensions, poweredByHeader, productionBrowserSourceMaps, publicRuntimeConfig, reactStrictMode, redirects, rewrites, sassOptions, serverRuntimeConfig, skipMiddlewareUrlNormalize, skipTrailingSlashRedirect, staticPageGenerationTimeout, swcMinify, trailingSlash, 
transpilePackages, typescript, useFileSystemPublicRoutes, webpack).
  - The root value has an unexpected property, optimizeImages, which is not in the list of allowed properties (amp, analyticsId, assetPrefix, basePath, cleanDistDir, compiler, compress, crossOrigin, devIndicators, distDir, env, eslint, excludeDefaultMomentLocales, experimental, exportPathMap, generateBuildId, generateEtags, headers, httpAgentOptions, i18n, images, modularizeImports, onDemandEntries, optimizeFonts, output, outputFileTracing, pageExtensions, poweredByHeader, productionBrowserSourceMaps, publicRuntimeConfig, reactStrictMode, redirects, rewrites, sassOptions, serverRuntimeConfig, skipMiddlewareUrlNormalize, skipTrailingSlashRedirect, staticPageGenerationTimeout, swcMinify, trailingSlash, transpilePackages, typescript, useFileSystemPublicRoutes, webpack).
  - The value at .amp.canonicalBase must be 1 character or more but it was 0 characters.
  - The value at .assetPrefix must be 1 character or more but it was 0 characters.
  - The value at .experimental.outputFileTracingRoot must be 1 character or more but it was 0 characters.
  - The value at .i18n must be an object but it was null.
  - The value at .reactStrictMode must be a boolean but it was null.

See more info here: https://nextjs.org/docs/messages/invalid-next-config

This seems to be caused by the next-compose-plugin.

I originally used this plugin to combine the configuration of multiple plugins as follows:

const withPlugins = require('next-compose-plugins');

const config = withPlugins(
  [
    [withTM()],
    [
      optimizedImages,
      {
        // optimisation disabled by default, to enable check https://github.com/cyrilwanner/next-optimized-images
        optimizeImages: false,
      },
    ],
  ],
  nextConfig
);

The best solution I found is to simply remove the plugin and replace it with the following code:

const plugins = [withTM];

module.exports = (_phase, { defaultConfig }) => {
  return plugins.reduce(
    (acc, plugin) => {
      if (Array.isArray(plugin)) {
        return plugin[0](acc, plugin[1]);
      }
      return plugin(acc);
    },
    { ...nextConfig }
  );
};

We can also fix the problem by refactoring the declaration of the plugin to:

const nextComposePlugins = require('next-compose-plugins');
const { withPlugins } = nextComposePlugins.extend(() => ({}));

Error: The root value has an unexpected property

I also encountered an issue with the next-optimized-images plugin: The root value has an unexpected property, optimizeImages, which is not in the list of allowed properties.

Here the full text of the error message:

warn  - Invalid next.config.js options detected: 
  - The root value has an unexpected property, optimizeImages, which is not in the list of allowed properties (amp, analyticsId, assetPrefix, basePath, cleanDistDir, compiler, compress, crossOrigin, devIndicators, distDir, env, eslint, excludeDefaultMomentLocales, experimental, exportPathMap, generateBuildId, generateEtags, headers, httpAgentOptions, i18n, images, modularizeImports, onDemandEntries, optimizeFonts, output, outputFileTracing, pageExtensions, poweredByHeader, productionBrowserSourceMaps, publicRuntimeConfig, reactStrictMode, redirects, rewrites, sassOptions, serverRuntimeConfig, skipMiddlewareUrlNormalize, skipTrailingSlashRedirect, staticPageGenerationTimeout, swcMinify, trailingSlash, transpilePackages, typescript, useFileSystemPublicRoutes, webpack).

See more info here: https://nextjs.org/docs/messages/invalid-next-config

I solved this by replacing the next-optimized-images plugin with the file-loader and svg-url-loader plugins as follows:

  const nextConfig = {
  webpack: (config, options) => {
    config.module.rules.push({
      test: /\.svg/,
      use: {
        loader: 'svg-url-loader',
      },
    });
    config.module.rules.push({
      test: /\.(png|jpe?g|gif)$/i,
      use: {
        loader: 'file-loader',
        options: {
          name: '[path][name].[hash].[ext]',
          publicPath: '/_next/static',
          outputPath: 'static',
          emitFile: !options.isServer,
        },
      },
    });
    return config;
  },

Bonus Error: Property 'forward' is missing

I also encountered one further issue not connected to the Next.js configuration file.

For one unit test, I create a mock instance of type NextRouter. After the upgrade, the following error came up:

src/__tests__/index.uispec.tsx:16:7 - error TS2322: Type '{ basePath: string; pathname: string; route: string; asPath: string; query: {}; isReady: true; push: jest.Mock<any, any>; replace: jest.Mock<any, any>; reload: jest.Mock<any, any>; ... 6 more ...; isFallback: false; }' is not assignable to type 'NextRouter'.
  Property 'forward' is missing in type '{ basePath: string; pathname: string; route: string; asPath: string; query: {}; isReady: true; push: jest.Mock<any, any>; replace: jest.Mock<any, any>; reload: jest.Mock<any, any>; ... 6 more ...; isFallback: false; }' but required in type 'Pick<Router, "replace" | "push" | "reload" | "back" | "forward" | "prefetch" | "beforePopState" | "events" | "isFallback" | "isReady" | "isPreview">'.

16 const mockRouter: NextRouter = {

This can be fixed by adding the property forward to the mocked NextRouter instance:

const mockRouter: NextRouter = {
  basePath: '',
  pathname: '/',
  route: '/',
  asPath: '/',
  // eslint-disable-next-line @typescript-eslint/no-empty-function
  forward: () => {},
  query: {},
  isReady: true,
  push: jest.fn(),
  replace: jest.fn(),
  reload: jest.fn(),
  back: jest.fn(),
  prefetch: jest.fn(),
  beforePopState: jest.fn(),
  isLocaleDomain: true,
  isPreview: true,
  events: {
    on: jest.fn(),
    off: jest.fn(),
    emit: jest.fn(),
  },
  isFallback: false,
};

Conclusion

Overall, upgrading from Next.js 12 to Next.js 13 was quite pain free and I was able to upgrade the templates and the Goldstack website in a matter of a few hours.

If you are interested how to get a complete end-to-end example of Next.js 13 working, please have a look at this automatically updated boilerplate project on GitHub: