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Dev Container / GitHub Codespaces (test)

This guide covers running prei in a VS Code Dev Container or GitHub Codespace — the test environment.

Prerequisites

Platform Requirement
GitHub Codespaces GitHub account, repo access
VS Code Dev Containers VS Code + "Dev Containers" extension + Docker Desktop

Quick Start

GitHub Codespaces (browser-based)

  1. Open the repo on GitHub
  2. Click Code → Codespaces → Create codespace on main
  3. Wait for build (~2 minutes)
  4. In the integrated terminal: 
    make dev
  5. Open the forwarded port 8000 (toast notification → "Open in Browser")
  6. Visit http://localhost:8000

VS Code Dev Container (local)

  1. Open repo in VS Code: code .
  2. Command Palette (Ctrl+Shift+P) → Dev Containers: Reopen in Container
  3. Wait for build
  4. Terminal → make dev
  5. Open forwarded port 8000

What Happens Automatically

The .devcontainer/devcontainer.json configures:

  • Base image: Built from root Dockerfile (Python 3.14, non-root app user)
  • Compose file: Uses root docker-compose.yml (SQLite, no Postgres)
  • Environment variables:
    • DATABASE_URL=sqlite:////home/vscode/db.sqlite3 (absolute path — writable by vscode user)
  • DEBUG=True, ALLOWED_HOSTS=*, SECRET_KEY=dev-secret-key-change-me
  • RUN_MIGRATIONS=1
  • Post-create: pip install -r requirements.txt && python manage.py migrate --noinput
  • Post-start: python manage.py check
  • Port forward: 8000 → labeled "Django app"

Database

  • SQLite at /home/vscode/db.sqlite3 (inside container, not the bind-mounted workspace)
  • Persists across container restarts but not across Codespace rebuilds
  • To reset: delete /home/vscode/db.sqlite3 and re-run make dev

Useful Commands

Command Purpose
make dev Run migrations + start Django runserver on 0.0.0.0:8000
make superuser Create admin user (first time only)
make lint Ruff + format check
make test Run pytest suite
make check manage.py check + lint + tests

Demo Login

Field Value
Email demo@prei.dev
Password DemoPass123!

Created by make dev via seed_data management command.

Troubleshooting

Port 8000 not forwarded

  • VS Code: Ports tab → check 8000 is listed → right-click → "Preview in Browser"
  • Codespaces: Ports panel → visibility → "Public" or "Private"

"DisallowedHost" error

  • Ensure ALLOWED_HOSTS=* is set (it is in devcontainer.json)
  • If using custom domain, add to ALLOWED_HOSTS in .env

Database "unable to open database file"

  • Fixed in devcontainer.json: DATABASE_URL=sqlite:////home/vscode/db.sqlite3 (absolute path)
  • The Dev Container uses mcr.microsoft.com/devcontainers/python (not the root Dockerfile) and runs as vscode, so /home/vscode/ is the writable home directory

Changes not reflecting

  • Dev container mounts workspace at /workspaces/prei but Django runs from /app
  • Code is copied into /app at build time (see Dockerfile COPY . .)
  • For live reload, use make dev which runs Django's runserver with auto-reload watching /app

Architecture Note

┌─────────────────────────────────────────────────────┐
│  GitHub Codespace / VS Code Dev Container           │
│  ┌─────────────────────────────────────────────┐   │
│  │  Workspace mount: /workspaces/prei (source)  │   │
│  └─────────────────────────────────────────────┘   │
│  ┌─────────────────────────────────────────────┐   │
│  │  Container FS: /app (Django runs here)       │   │
│  │    ├── db.sqlite3  ← writable (chowned)      │   │
│  │    └── ...                                    │   │
│  └─────────────────────────────────────────────┘   │
└─────────────────────────────────────────────────────┘

The source is mounted at /workspaces/prei for git/editor access, but the runtime code lives at /app (copied during docker build). The Dev Container uses its own Dockerfile (.devcontainer/Dockerfile) based on mcr.microsoft.com/devcontainers/python:1-3.13-bookworm. The database goes to /home/vscode/db.sqlite3 — the vscode user's home directory — because the devcontainer runs as vscode, not app.