Next.JS Build Hangs in Docker with Tailwind v4

[AChangXD]

Summary

I upgraded from Tailwind v3 to v4 in my repo, and now the build is failing. I tried to create a new repo using create-next-app, and put my Dockerfile into it. The result? The build just hangs and eventually run out of memory. My Dockerfile is:

FROM node:20 AS base

# Set the working directory
WORKDIR /

# Copy package.json and package-lock.json
COPY package*.json ./

# Copy the rest of the application code
COPY . .

# Install dependencies
RUN npm install --legacy-peer-deps

# Build the Next.js application
RUN npm run build

# ---------------------------------------------------------------------------- #
#                                   DB Backup                                  #
# ---------------------------------------------------------------------------- #
# For fetching AWS credentials:
RUN npm install -g dotenv-cli

CMD ["sh", "-c", "npm run start"]

Only fails on tailwind v4, but not v3. The normal next build executes properly

Additional information

No response

Example

[AChangXD]

Reproduction here: https://github.com/AChangXD/tailwind-v4-docker-build-test

[AChangXD]

@leerob Would this be an issue with Next or tailwind v4? next build works fine outside of Docker.

[icyJoseph]

Hej! Lee doesn't work at Vercel anymore. I will take a look at this and see what info we can grab.

[icyJoseph]

I think the new auto detection of CSS classnames in TW 4 is getting tricked into parsing the entire root of the host, right?

# Set the working directory
WORKDIR /root

# Copy package.json and package-lock.json
COPY package*.json /root

# Copy the rest of the application code
COPY . /root

In TW 3 you'd specify the paths to scan, but since TW 4 is config less cuz it auto scans, the placement of the application code matters now.

[AChangXD]

Yep that was it, thanks!