Invalid next config warning in Server Components

[EverStarck]

Description

Apparently everything works but there is a warning message in console:

- warn Invalid next.config.mjs options detected: 
- warn     The root value has an unexpected property, 0, which is not in the list of allowed properties (amp, analyticsId, assetPrefix, basePath, cleanDistDir, compiler, compress, configOrigin, crossOrigin, devIndicators, distDir, env, eslint, excludeDefaultMomentLocales, experimental, exportPathMap, generateBuildId, generateEtags, headers, httpAgentOptions, i18n, images, modularizeImports, onDemandEntries, optimizeFonts, output, outputFileTracing, pageExtensions, poweredByHeader, productionBrowserSourceMaps, publicRuntimeConfig, reactProductionProfiling, reactStrictMode, redirects, rewrites, sassOptions, serverRuntimeConfig, skipMiddlewareUrlNormalize, skipTrailingSlashRedirect, staticPageGenerationTimeout, swcMinify, target, trailingSlash, transpilePackages, typescript, useFileSystemPublicRoutes, webpack).

Mandatory reproduction URL (CodeSandbox or GitHub repository)

https://codesandbox.io/p/sandbox/next-intl-bug-template-app-forked-8g4r8r

Reproduction description

Steps to reproduce:

1. Open reproduction
2. See the terminal

Expected behaviour

No warning messages

[amannn]

There seems to be a small typo in your example:

import withNextIntl from 'next-intl/plugin';

/** @type {import('next').NextConfig} */
const nextConfig = withNextIntl("./i18n.ts", {
  reactStrictMode: true,
  experimental: {
    appDir: true,
  },
});

export default nextConfig;

withNextIntl doesn't accept a second argument, but instead returns a function that accepts any custom Next.js config you might have. This is less obvious when using CommonJS, but ESM makes this very explicit.

Here's a working example:

import NextIntlPlugin from 'next-intl/plugin';

/** @type {import('next').NextConfig} */
const nextConfig = {
  reactStrictMode: true,
  experimental: {
    appDir: true
  }
};

const withNextIntl = NextIntlPlugin('./i18n.ts');
export default withNextIntl(nextConfig);

Hope this helps!