# Prettier: YAML & CSS Formatter

`Prettier` is an opinionated code formatter. Zenith uses Prettier exclusively through `prek` to format GitHub Actions YAML manifests, issue templates, and custom CSS stylesheets.

## What It Does

Prettier parses configuration files and stylesheets, re-printing them to adhere to strict stylistic standards. In Zenith, it standardizes 4-space indentation, list formatting, key-value spacing, and scalar wrapping across GitHub Actions workflows (`.github/workflows/*.yaml`) and custom CSS sheets (`docs/stylesheets/*.css`).

By formatting files automatically, Prettier completely eliminates stylistic noise from pull request reviews and version control diffs.

## Why It's in Zenith

Zenith enforces consistent 4-space indentation across all languages in the project (Python, TOML, YAML, and CSS). Prek runs Prettier mirrors directly, executing formatting without requiring a global Node.js installation or package manifests in the Python repository.

It integrates directly into dedicated task runners (`poe format-yaml`, `poe format-css`) and the overarching `poe code-quality` verification pipeline.

## Configuration in Zenith

Configured in `.prettierrc.yaml` at the project root:

```yaml
# ==============================================================================
# Prettier Configuration (.prettierrc.yaml)
#
# Tool: Prettier (https://prettier.io/)
# Purpose: Opinionated code and data formatter.
# Why it's in Zenith: Enforces consistent 4-space indentation, 88-character line
# length, and clean formatting across all YAML manifests and CSS stylesheets.
# ==============================================================================

printWidth: 88
tabWidth: 4
useTabs: false
semi: true
singleQuote: false
bracketSpacing: true
proseWrap: "preserve"
```

And registered in `prek.toml`:

```toml
[[repos]]
repo = "https://github.com/pre-commit/mirrors-prettier"
rev = "v4.0.0-alpha.8"
hooks = [
    { id = "prettier", name = "🎨 prettier · Format YAML files", types = ["yaml"] },
    { id = "prettier", name = "🎨 prettier · Format CSS files", types = ["css"] },
]
```

## Key Invocations

```bash
uv run poe format-yaml       # Format YAML configuration files
uv run poe format-css        # Format CSS stylesheets
uv run poe fix               # Auto-fix all files including YAML and CSS
```

## Upstream Documentation

- [Prettier Official Documentation](<https://prettier.io/>)
- [Prettier Configuration Options](<https://prettier.io/docs/en/options.html>)