Why does my custom next.config break Standalone build in Docker?

[zanzlender]

Summary

Like the title says I cannot build my Docker image when I have a custom next config, and I don't know why.

I took the example Dockerfile from the with-docker example, with some minor adjustments:

FROM node:20-alpine3.18 AS base

# Install dependencies only when needed
FROM base AS deps
# Check https://github.com/nodejs/docker-node/tree/b4117f9333da4138b03a546ec926ef50a31506c3#nodealpine to understand why libc6-compat might be needed.
RUN apk add --no-cache libc6-compat
WORKDIR /app

# Install dependencies based on the preferred package manager
COPY package.json yarn.lock* package-lock.json* pnpm-lock.yaml* ./
RUN \
  if [ -f yarn.lock ]; then yarn --frozen-lockfile; \
  elif [ -f package-lock.json ]; then npm ci; \
  elif [ -f pnpm-lock.yaml ]; then corepack enable pnpm && pnpm i --frozen-lockfile; \
  else echo "Lockfile not found." && exit 1; \
  fi

# Rebuild the source code only when needed
FROM base AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .

# Next.js collects completely anonymous telemetry data about general usage.
# Learn more here: https://nextjs.org/telemetry
# Uncomment the following line in case you want to disable telemetry during the build.
ENV NEXT_TELEMETRY_DISABLED 1

# Check which package manager is used then generate Prisma types
RUN \
  if [ -f yarn.lock ]; then yarn run prisma:generate; \
  elif [ -f package-lock.json ]; then npm run prisma:generate; \
  elif [ -f pnpm-lock.yaml ]; then pnpm run prisma:generate; \
  else echo "Lockfile not found." && exit 1; \
  fi

# Build the app
RUN \
  if [ -f yarn.lock ]; then yarn run build; \
  elif [ -f package-lock.json ]; then npm run build; \
  elif [ -f pnpm-lock.yaml ]; then corepack enable pnpm && pnpm run build; \
  else echo "Lockfile not found." && exit 1; \
  fi

# Production image, copy all the files and run next
FROM base AS runner
WORKDIR /app

ENV NODE_ENV production
# Uncomment the following line in case you want to disable telemetry during runtime.
# ENV NEXT_TELEMETRY_DISABLED 1

RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs

COPY --from=builder /app/public ./public
COPY --from=builder /app/next.config.mjs ./

# Set the correct permission for prerender cache
RUN mkdir .next
RUN chown nextjs:nodejs .next

# Automatically leverage output traces to reduce image size
# https://nextjs.org/docs/advanced-features/output-file-tracing
COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static

USER nextjs

#EXPOSE 3000

#ENV PORT 3000

# server.js is created by next build from the standalone output
# https://nextjs.org/docs/pages/api-reference/next-config-js/output
#CMD HOSTNAME="0.0.0.0" node server.js

For reference this is my next.config.mjs

// @ts-check
!process.env.SKIP_ENV_VALIDATION && (await import("./src/env/server.mjs"));
import NextBundleAnalyzer from "@next/bundle-analyzer";

/** @type {import("next").NextConfig} */
const config = {
  output: "standalone",
  reactStrictMode: true,
  swcMinify: true,
};

const withBundleAnalyzer = NextBundleAnalyzer({
  enabled: !!process.env.ANALYZE == true,
  ...config,
});
const bundledConfig = withBundleAnalyzer();
// Here I just export the "default" config.
export default config;

And like this everything works. However when I try to add a wrapper around the config like so:

const withBundleAnalyzer = NextBundleAnalyzer({
  enabled: !!process.env.ANALYZE == true,
  ...config,
});
const bundledConfig = withBundleAnalyzer();
export default bundledConfig ;

I get this error: standalone not found... I suspect that the config is not loaded properly - or the NextBundleAnalyzer() is not run while when the config is loaded, but I don't know how to fix this...

** => ERROR [tasky runner 8/9] COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./                          0.0s 
------
 > [tasky runner 8/9] COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./:
------
failed to solve: failed to compute cache key: failed to calculate checksum of ref 02cd46ed-7d19-4b05-b07a-2a54af95bc9c::rduxdljumdgy5zysy3bn8ayc9: "/app/.next/standalone": not found**

Additional information

No response

Example

No response

[zanzlender]

I have confirmed inside the container that there is actually no standalone folder anywhere on the FS

[SouthLink]

I think it's because the output: "standalone" configuration is broken，Without this configuration, the component will not have the "/app/.next/standalone" folder。

After reading the plug-in documentation, I think you should be able to change the configuration to this:

const withBundleAnalyzer = NextBundleAnalyzer({
  enabled: !!process.env.ANALYZE == true,
});
const bundledConfig = withBundleAnalyzer({
   ...config
});
export default bundledConfig ;

[zanzlender]

Thank you very much! It seems the config needs to be included when calling the method 😂