withMonolithicPortability

withMonolithicPortability(
  nextConfig?: NextConfig,
  options?: PortabilityOptions
): NextConfig

Checks, from inside an app, that it could be mounted into a monolith. Returns the config unchanged — it only reports.

// apps/id/next.config.ts
import { withMonolithicPortability } from '@fairgarden/monolith'

export default withMonolithicPortability(nextConfig)

This app would not port cleanly into a monolith:
  - proxy.ts: a deployment has one proxy; the monolith would have to run it
    and strip the mount prefix itself
See @fairgarden/monolith for what a mounted app can rely on.

Options

| Field | Default | Meaning | | --- | --- | --- | | root | process.cwd() | where to look | | level | 'warn' | 'error' throws instead of reporting | | ignore | [] | findings to accept, by the text before the colon |

withMonolithicPortability(nextConfig, {
  level: 'error',
  ignore: ['proxy.ts'],
})

'warn' keeps it a reminder while working on the app; set 'error' in CI to make it a gate.

What it reports

Config the monolith owns — basePath and distDir, which would fight the monolith, since a mounted app is served from its mount point instead.

Config that has to be shared — i18n, trailingSlash, skipTrailingSlashRedirect, skipMiddlewareUrlNormalize, output and assetPrefix. One server serves every app, so these have to agree, which means they belong on the monolith.

Conventions a deployment only gets one of — proxy/middleware, instrumentation, pages/_app and pages/_document, looked for at the app root and under src/. An app can use these on its own, but mounting several apps means only one could ever win, so rather than let one app's copy silently disappear it says so.

Routes that only work at the site root — robots, sitemap and manifest under app/ or src/app/, which end up at /<name>/robots.txt where nothing looks for them.

Notes

Next reads the config in the main process and again in a build worker. The report is marked in the environment so the worker, which inherits it, stays quiet — it appears once per build.

For the list as data rather than log output, use findPortabilityProblems.