app/assets.py

"""Release-stamped asset URLs for the page.

Every /static/... URL in index.html gets ?v=<release>, so each release has its own addresses and a browser can
never run a stale app.js or app.css cached from an older release (1.8.x files were served without cache headers).
Pure Python: tested anywhere.
"""
from __future__ import annotations

import re

_ASSET = re.compile(r'(["\'])(/static/[^"\'?#]+)\1')


def stamp_assets(html: str, version: str) -> str:
    v = re.sub(r"[^A-Za-z0-9._-]+", "-", version)
    return _ASSET.sub(lambda m: f"{m.group(1)}{m.group(2)}?v={v}{m.group(1)}", html)