How to fix failed to solve with frontend dockerfile.v0: failed to build LLB: failed to parse stage name in Docker

# Wrong - uppercase stage names
FROM node:20-alpine AS BUILD
WORKDIR /app
COPY package*.json ./
RUN npm ci

FROM node:20-alpine AS RUNTIME
COPY --from=BUILD /app/node_modules ./node_modules

# Correct - lowercase stage names
FROM node:20-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm ci

FROM node:20-alpine AS runtime
COPY --from=build /app/node_modules ./node_modules

# Wrong - ARG after FROM
FROM node:${NODE_VERSION}-alpine
ARG NODE_VERSION=20

# Correct - ARG before FROM
ARG NODE_VERSION=20
FROM node:${NODE_VERSION}-alpine

ARG NODE_VERSION=20
FROM node:${NODE_VERSION}-alpine AS build
ARG NODE_VERSION  # Re-declare to use in this stage
RUN echo "Building with Node ${NODE_VERSION}"

# Check if the ARG has a default value
# If not, you must pass it at build time

# Wrong - missing required argument
docker build -t myapp .

# Correct - passing the argument
docker build --build-arg NODE_VERSION=20 -t myapp .

# Or set a default in Dockerfile
ARG NODE_VERSION=20  # Default value if not provided
FROM node:${NODE_VERSION}-alpine

services:
  app:
    build:
      context: .
      args:
        NODE_VERSION: "20"

# Debug: Check what value is being used
docker build --build-arg NODE_VERSION=20 -t myapp . --progress=plain

# In CI, verify environment variables are set
echo "NODE_VERSION=${NODE_VERSION}"

# GitHub Actions - variable might be empty
- name: Build
  run: |
    # Verify the variable exists
    if [ -z "${{ env.VERSION }}" ]; then
      echo "VERSION is not set!"
      exit 1
    fi
    docker build --build-arg VERSION=${{ env.VERSION }} -t app .

# Invalid stage names
FROM alpine AS 1stStage      # Cannot start with number
FROM alpine AS my-Stage      # Contains uppercase
FROM alpine AS my@stage      # Contains invalid symbol
FROM alpine AS MY_BUILD      # All uppercase

# Valid stage names
FROM alpine AS stage1
FROM alpine AS my-stage
FROM alpine AS my_stage
FROM alpine AS build.dev
FROM alpine AS base

# Wrong - two colons
FROM node:20-alpine:latest

# Correct - single colon
FROM node:20-alpine
# or
FROM node:latest

# Wrong - if TAG already contains a colon
ARG TAG=20-alpine
FROM node:${TAG}:latest  # Results in node:20-alpine:latest

# Correct
ARG TAG=20-alpine
FROM node:${TAG}

# Check for Windows line endings
file Dockerfile
# If it shows "with CRLF line terminators", convert it:

# Using sed
sed -i 's/\r$//' Dockerfile

# Using dos2unix
dos2unix Dockerfile

# In VS Code: Click "CRLF" in status bar and select "LF"

# .gitattributes
Dockerfile text eol=lf
*.sh text eol=lf

# docker-compose.yml
services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
      args:
        # Explicitly set all ARGs
        NODE_VERSION: "20"
        # Or reference environment variables
        BUILD_ENV: ${BUILD_ENV:-production}

# .env file
NODE_VERSION=20

# Verify variables are loaded
docker compose config