feat(generator): generate Docker artifacts for NestJS

[dev-queiroz]

Summary

Generate production-ready Dockerfile and docker-compose.yml for containerized NestJS deployment.

Motivation

To be truly "generated and runnable", applications must work in containers. This feature generates all Docker artifacts so developers can deploy with docker-compose up.

Scope

In Scope

• Multi-stage Dockerfile (build + runtime stages)
• docker-compose.yml with NestJS + PostgreSQL
• Environment variable configuration
• Health check in docker-compose
• Volume mounts for development (live reload)
• .dockerignore file
• Production-ready image (minimal, non-root user)
• Can run with docker-compose up immediately

Out of Scope

• Kubernetes manifests (future)
• CI/CD pipeline generation
• Docker registry configuration
• Secrets management

Acceptance Criteria

• Dockerfile generated with multi-stage build
• Base image: node:20-alpine (production), node:20 (dev)
• Non-root user created in Dockerfile
• docker-compose.yml generated with services: app + postgres
• PostgreSQL image: postgres:15-alpine
• Health check defined in docker-compose
• Environment variables passed to app container
• Volume mounts for development (src/ mounted)
• .dockerignore excludes node_modules, dist, .env
• Build succeeds: docker-compose build
• App starts: docker-compose up
• Database accessible from app container
• Health endpoint returns 200 from container

Files to Create/Modify

• packages/generators/src/nest/templates/Dockerfile.template (NEW)
• packages/generators/src/nest/templates/docker-compose.template.yml (NEW)
• packages/generators/src/nest/templates/.dockerignore (NEW)
• packages/generators/src/nest/generator.ts (MODIFY)
• tests/docker-generation.test.mjs (NEW)

Example Output

Dockerfile

FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:20-alpine
WORKDIR /app
RUN addgroup -g 1001 -S nodejs && adduser -S nodejs -u 1001
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY .env.example .env
USER nodejs
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \\
  CMD node -e \"require('http').get('http://localhost:3000/health', (r) => {if (r.statusCode !== 200) throw new Error(r.statusCode)})\"
CMD [\"node\", \"dist/main.js\"]

docker-compose.yml

version: '3.8'
services:
  app:
    build: .
    ports:
      - \"3000:3000\"
    environment:
      NODE_ENV: development
      DATABASE_URL: postgresql://postgres:postgres@postgres:5432/forge
    depends_on:
      - postgres
    volumes:
      - ./src:/app/src
      - /app/node_modules
    healthcheck:
      test: [\"CMD\", \"curl\", \"-f\", \"http://localhost:3000/health\"]
      interval: 30s
      timeout: 10s
      retries: 3

  postgres:
    image: postgres:15-alpine
    environment:
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: forge
    volumes:
      - postgres_data:/var/lib/postgresql/data

volumes:
  postgres_data:

Test Strategy

• Generate Docker artifacts from contract
• Build Docker image: docker build -t forge-app .
• Verify image builds successfully
• Start with docker-compose: docker-compose up
• Verify app accessible on port 3000
• Verify database connectivity from app
• Test health endpoint returns 200
• Verify volume mounts work (live reload ready)
• Verify clean shutdown on SIGTERM