devcontainer-setup

# Devcontainer Setup Skill Creates a pre-configured devcontainer with Claude Code and language-specific tooling. ## When to Use - User asks to "set up a devcontainer" or "add devcontainer support" - User wants a sandboxed Claude Code development environment - User needs isolated development environments with persistent configuration ## When NOT to Use - User already has a devcontainer configuration and just needs modifications - User is asking about general Docker or container questions - User wants to deploy production containers (this is for development only) ## Workflow ```mermaid flowchart TB start([User requests devcontainer]) recon[1. Project Reconnaissance] detect[2. Detect Languages] generate[3. Generate Configuration] write[4. Write files to .devcontainer/] done([Done]) start --> recon recon --> detect detect --> generate generate --> write write --> done ``` ## Phase 1: Project Reconnaissance ### Infer Project Name Check in order (use first match): 1. `package.json` → `name` field 2. `pyproject.toml` → `project.name` 3. `Cargo.toml` → `package.name` 4. `go.mod` → module path (last segment after `/`) 5. Directory name as fallback Convert to slug: lowercase, replace spaces/underscores with hyphens. ### Detect Language Stack | Language | Detection Files | |----------|-----------------| | Python | `pyproject.toml`, `*.py` | | Node/TypeScript | `package.json`, `tsconfig.json` | | Rust | `Cargo.toml` | | Go | `go.mod`, `go.sum` | ### Multi-Language Projects If multiple languages are detected, configure all of them in the following priority order: 1. **Python** - Primary language, uses Dockerfile for uv + Python installation 2. **Node/TypeScript** - Uses devcontainer feature 3. **Rust** - Uses devcontainer feature 4. **Go** - Uses devcontainer feature For multi-language `postCreateCommand`, chain all setup commands: ``` uv run /opt/post_install.py && uv sync && npm ci ``` Extensions and settings from all detected languages should be merged into the configuration. ## Phase 2: Generate Configuration Start with base templates from `resources/` directory. Substitute: - `{{PROJECT_NAME}}` → Human-readable name (e.g., "My Project") - `{{PROJECT_SLUG}}` → Slug for volumes (e.g., "my-project") Then apply language-specific modifications below. ## Base Template Features The base template includes: - **Claude Code** with marketplace plugins (anthropics/skills, trailofbits/skills, trailofbits/skills-curated) - **Python 3.13** via uv (fast binary download) - **Node 22** via fnm (Fast Node Manager) - **ast-grep** for AST-based code search - **Network isolation tools** (iptables, ipset) with NET_ADMIN capability - **Modern CLI tools**: ripgrep, fd, fzf, tmux, git-delta --- ## Language-Specific Sections ### Python Projects **Detection:** `pyproject.toml`, `requirements.txt`, `setup.py`, or `*.py` files **Dockerfile additions:** The base Dockerfile already includes Python 3.13 via uv. If a different version is required (detected from `pyproject.toml`), modify the Python installation: ```dockerfile # Install Python via uv (fast binary download, not source compilation) RUN uv python install <version> --default ``` **devcontainer.json extensions:** Add to `customizations.vscode.extensions`: ```json "ms-python.python", "ms-python.vscode-pylance", "charliermarsh.ruff" ``` Add to `customizations.vscode.settings`: ```json "python.defaultInterpreterPath": ".venv/bin/python", "[python]": { "editor.defaultFormatter": "charliermarsh.ruff", "editor.codeActionsOnSave": { "source.organizeImports": "explicit" } } ``` **postCreateCommand:** If `pyproject.toml` exists, chain commands: ``` rm -rf .venv && uv sync && uv run /opt/post_install.py ``` --- ### Node/TypeScript Projects **Detection:** `package.json` or `tsconfig.json` **No Dockerfile additions needed:** The base template includes Node 22 via fnm (Fast Node Manager). **devcontainer.json extensions:** Add to `customizations.vscode.extensions`: ```json "dbaeumer.vscode-eslint", "esbenp.prettier-vscode" ``` Add to `customizations.vscode.settings`: ```json "editor.defaultFormatter": "esbenp.prettier-vscode", "editor.codeActionsOnSave": { "source.fixAll.eslint": "explicit" } ``` **postCreateCommand:** Detect package manager from lockfile and chain with base command: - `pnpm-lock.yaml` → `uv run /opt/post_install.py && pnpm install --frozen-lockfile` - `yarn.lock` → `uv run /opt/post_install.py && yarn install --frozen-lockfile` - `package-lock.json` → `uv run /opt/post_install.py && npm ci` - No lockfile → `uv run /opt/post_install.py && npm install` --- ### Rust Projects **Detection:** `Cargo.toml` **Features to add:** ```json "ghcr.io/devcontainers/features/rust:1": {} ``` **devcontainer.json extensions:** Add to `customizations.vscode.extensions`: ```json "rust-lang.rust-analyzer", "tamasfe.even-better-toml" ``` Add to `customizations.vscode.settings`: ```json "[rust]": { "editor.defaultFormatter": "rust-lang.rust-analyzer" } ``` **postCreateCommand:** If `Cargo.lock` exists, use locked builds: ``` uv run /opt/post_install.py && cargo build --locked ``` If no lockfile, use standard build: ``` uv run /opt/post_install.py && cargo build ``` --- ### Go Projects **Detection:** `go.mod` **Features to add:** ```json "ghcr.io/devcontainers/features/go:1": { "version": "latest" } ``` **devcontainer.json extensions:** Add to `customizations.vscode.extensions`: ```json "golang.go" ``` Add to `customizations.vscode.settings`: ```json "[go]": { "editor.defaultFormatter": "golang.go" }, "go.useLanguageServer": true ``` **postCreateCommand:** ``` uv run /opt/post_install.py && go mod download ``` --- ## Reference Material For additional guidance, see: - `references/dockerfile-best-practices.md` - Layer optimization, multi-stage builds, architecture support - `references/features-vs-dockerfile.md` - When to use devcontainer features vs custom Dockerfile --- ## Adding Persistent Volumes Pattern for new mounts in `devcontainer.json`: ```json "mounts": [ "source={{PROJECT_SLUG}}-<purpose>-${devcontainerId},target=<container-path>,type=volume" ] ``` Common additions: - `source={{PROJECT_SLUG}}-cargo-${devcontainerId},target=/home/vscode/.cargo,type=volume` (Rust) - `source={{PROJECT_SLUG}}-go-${devcontainerId},target=/home/vscode/go,type=volume` (Go) --- ## Output Files Generate these files in the project's `.devcontainer/` directory: 1. `Dockerfile` - Container build instructions 2. `devcontainer.json` - VS Code/devcontainer configuration 3. `post_install.py` - Post-creation setup script 4. `.zshrc` - Shell configuration 5. `install.sh` - CLI helper for managing the devcontainer (`devc` command) --- ## Validation Checklist Before presenting files to the user, verify: 1. All `{{PROJECT_NAME}}` placeholders are replaced with the human-readable name 2. All `{{PROJECT_SLUG}}` placeholders are replaced with the slugified name 3. JSON syntax is valid in `devcontainer.json` (no trailing commas, proper nesting) 4. Language-specific extensions are added for all detected languages 5. `postCreateCommand` includes all required setup commands (chained with `&&`) --- ## User Instructions After generating, inform the user: 1. How to start: "Open in VS Code and select 'Reopen in Container'" 2. Alternative: `devcontainer up --workspace-folder .` 3. CLI helper: Run `.devcontainer/install.sh self-install` to add the `devc` command to PATH ## Limitations - Use this skill only when the task clearly matches the scope described above. - Do not treat the output as a substitute for environment-specific validation, testing, or expert review. - Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.