baseline-warden

Pre-commit/CI guardrail for Baseline support in HTML/CSS. Scans your code, maps features to Web Baseline (Web Status + MDN BCD), and flags anything not widely/newly available.

Quick start

Install uv (one‑liner):

curl -LsSf https://astral.sh/uv/install.sh | sh

Install Baseline Warden from PyPI with uv and scan:

uv venv .venv && source .venv/bin/activate
uv pip install baseline-warden

bw sync --lock                   # build a Baseline snapshot
bw scan --out console,json       # fails on limited; warns on unknown
# Tip: add --summary-only for compact console output

Supported Python versions: 3.11, 3.12, and 3.13. The example workflows use Python 3.13, and CI tests all three.

What it checks

• Files: .html/.htm/.jinja/.jinja2 and .css (others ignored)
• Findings: Baseline status per BCD key (widely/newly/limited/unknown)
• Outputs: console (use --summary-only to keep it brief), report.json, GitHub annotations
• Noise control: ignores global HTML attrs (class/id/aria-*), custom property declarations (--foo), descriptor-only at‑rules (@font-face/@counter-style/@page); falls back value→property when helpful

Integrations

• Pre-commit (blocking by default):

  - repo: local
    hooks:
      - id: baseline-warden
        name: baseline-warden
        entry: bw scan --out console --summary-only --config baseline-warden.toml
        language: system
        files: '\\.(html|htm|jinja|jinja2|css)$'
  

GitHub Actions (minimal working example):

name: Baseline Warden

on:
  pull_request:
  push:
    branches:
      - main

jobs:
  baseline:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4

      - name: Set up Python
        uses: actions/setup-python@v5
        with:
          python-version: "3.13"

      - name: Install uv
        run: pip install uv

      - name: Sync dependencies
        run: uv sync --locked

      - name: Run Baseline scan
        run: uv run bw scan --out console --ci

• Ensure baseline.lock.json is committed (recommended). If you prefer to build it in CI, add a step before the scan: uv run bw sync --lock.

Configuration

Defaults usually “just work” for common layouts. For full options and examples, see the Configuration guide: docs/CONFIG.md.

Contributing

See the contributing guide: CONTRIBUTING.md for developer setup and guidelines.