Docker Compose: The "Hh" variable is not set. Defaulting to a blank string

Question

I recently dockerized my Next.js application. Everything works so far but every time I docker compose up, I receive these weird warnings about variables that I never used and are nowhere to be found:

docker-compose up
WARN[0000] The "Hh" variable is not set. Defaulting to a blank string. 
WARN[0000] The "xG" variable is not set. Defaulting to a blank string. 
WARN[0000] The "Hh" variable is not set. Defaulting to a blank string. 
WARN[0000] The "xG" variable is not set. Defaulting to a blank string. 
[+] Running 3/2
 ✔ Network hey-shop_default       Created                                                0.0s 
 ✔ Container hey-shop-postgres-1  Created                                                0.1s 
 ✔ Container hey-shop-web-1       Created                                                0.0s 
Attaching to postgres-1, web-1

This is my docker-compose.yml:

services:
  postgres:
    image: postgres
    restart: always
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: postgres
    ports:
      - 5432:5432
    volumes:
      - postgres-data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "sh -c 'pg_isready -U postgres -d postgres'"]
      interval: 10s
      timeout: 3s
      retries: 3

  web:
    build:
      context: .
      args:
        - VERCEL_TOKEN=${VERCEL_TOKEN}
    volumes:
      - .:/app
    ports:
      - 3000:3000
      - 5555:5555
    depends_on:
      - postgres

volumes:
  postgres-data:

My Dockerfile:

FROM node:20

WORKDIR /app

COPY package.json ./

RUN npm install

RUN npm install --global vercel@latest

COPY . .

ARG VERCEL_TOKEN
RUN vercel env pull .env --environment=Development --token=$VERCEL_TOKEN

RUN DISABLE_ERD=true npx prisma generate --schema ./prisma/schema.prisma

ENV POSTGRES_DATABASE=postgres
ENV POSTGRES_USER=postgres
ENV POSTGRES_PASSWORD=postgres
ENV POSTGRES_HOST=postgres
ENV POSTGRES_URL=postgres://postgres:postgres@postgres:5432/postgres?connect_timeout=300&schema=public
ENV POSTGRES_PRISMA_URL=postgres://postgres:postgres@postgres:5432/postgres?connect_timeout=300&schema=public
ENV POSTGRES_URL_NON_POOLING=postgres://postgres:postgres@postgres:5432/postgres?connect_timeout=300&schema=public
ENV POSTGRES_PORT=5432

EXPOSE 3000

CMD ["npm", "run", "dev"]

This is my .dockerignore:

node_modules
.next
.swc
.env

I work on an Apple M chip and dockerize using Ubuntu 20

I tried completely purging the containers and rebuilding but this appears every time. I don't know if this is something that will give me trouble down the road or if I can ignore it. Either way it seems like something doesn't work as it should.

Answer 1

Thanks to Hans and AymDev, this oversight from me was quickly resolved.

I had in fact a secret set in .env that contained the mentioned "variables":

JWT_SECRET="[...]$Hh[...]$xG[...]"

As I pull the secrets using my Dockerfile, I could remove the entire .env and the warnings disappeared.