prek

name	prek
plugin	coding
description	Set up code formatting and pre-commit hooks using prek (fast Rust-based alternative to pre-commit) with prek.toml config. Use whenever the user wants to configure prek, add formatters, set up pre-commit hooks, or enforce code style. Triggers on "set up prek", "add formatting", "configure formatters", "pre-commit setup", "add ruff", "set up prettier", "configure sqlfmt". Works on new and existing projects. Always use when init-app-stack has just run.

Prek — Pre-commit Formatter Setup

prek is a fast, Rust-native drop-in alternative to pre-commit. It reads prek.toml and runs formatters automatically on staged files at commit time.

Formatters — all use 4 spaces, no tabs, line-length 120:

• Python: ruff-check --fix + ruff-format (via astral-sh/ruff-pre-commit)
• SQL: uv run sqlfmt (local hook)
• TypeScript/JS: bunx --bun prettier --write (local hook)
• YAML: builtin check-yaml (if .yaml/.yml files present)

---

Step 0: Ensure prek is installed

prek --version

If not installed, the simplest install for this stack is:

uv tool install prek

Other options: brew install prek, winget install --id j178.Prek, or download binary from https://github.com/j178/prek/releases.

---

Step 1: Detect file types in the project

find . -name "*.py"  -not -path "./.git/*" -not -path "./node_modules/*" | head -1
find . -name "*.sql" -not -path "./.git/*" | head -1
find . \( -name "*.ts" -o -name "*.tsx" -o -name "*.js" -o -name "*.jsx" \) \
  -not -path "./.git/*" -not -path "./node_modules/*" | head -1
find . \( -name "*.yaml" -o -name "*.yml" \) -not -path "./.git/*" | head -1

Include a repo/hook only when matching files exist. On a freshly scaffolded project with no files yet, use the declared stack to decide.

---

Step 2: Write prek.toml

Write prek.toml to the project root. The structure mirrors pre-commit's [[repos]] / hooks model — each [[repos]] block is a hook source.

# prek.toml — pre-commit formatter configuration
# Install git hook: prek install
# Format all files: prek run --all-files

[[repos]]                                 # include only if .yaml/.yml present
repo = "builtin"
hooks = [
    { id = "check-yaml" },
]

[[repos]]                                 # include only if .py files present
repo = "https://github.com/astral-sh/ruff-pre-commit"
rev = "v0.11.0"                           # verify: https://github.com/astral-sh/ruff-pre-commit/releases
hooks = [
    { id = "ruff-check", args = ["--fix"] },
    { id = "ruff-format" },
]

[[repos]]                                 # include only if .sql files present
repo = "local"
hooks = [
    { id = "sqlfmt", name = "sqlfmt", language = "system", entry = "uv run sqlfmt", files = '\\.sql$' },
]

[[repos]]                                 # include only if .ts/.tsx/.js/.jsx present
repo = "local"
hooks = [
    { id = "prettier", name = "prettier", language = "system", entry = "bunx --bun prettier --write", files = '\\.(ts|tsx|js|jsx|vue)$' },
]

Tip on ruff rev: run uv run ruff --version in the project to see the installed version, then use the matching tag from the ruff-pre-commit releases.

---

Step 3: Update pyproject.toml

If pyproject.toml exists or Python files are present, add/merge these sections. Don't overwrite keys the user already set:

[tool.ruff]
line-length = 120
indent-width = 4
target-version = "py313"

[tool.ruff.format]
indent-style = "space"
quote-style = "double"
line-ending = "auto"

[tool.sqlfmt]
line_length = 120

---

Step 4: Write .prettierrc

If TypeScript/JavaScript files are present, write .prettierrc to the project root (skip if one already exists with different settings — ask first):

{
  "tabWidth": 4,
  "useTabs": false,
  "semi": true,
  "singleQuote": false,
  "printWidth": 120,
  "trailingComma": "es5"
}

---

Step 5: Install the git hook

prek install

This writes .git/hooks/pre-commit automatically — no manual hook file needed.

---

Step 6: Run formatters on all existing files

prek run --all-files

If a tool is missing (prek not found, uv not installed, bunx not available), report it clearly and suggest the install command. Don't fail silently.

---

After setup — tell the user

• Which hooks were installed and why (based on detected file types)
• prek run --all-files runs all hooks manually on every file
• The git hook fires automatically on git commit
• What was added/merged into pyproject.toml