report-render

name	report-render
description	Render a report in a headless browser. Works offline by bundling Marimo assets.

Rendering a report to check it

A marimo export html bundle loads its frontend runtime (~200 JS/CSS/font URLs) from cdn.jsdelivr.net/npm/@marimo-team/frontend@<version>/dist. In a network-restricted sandbox the browser can't reach that CDN, so the page stays blank — you can't screenshot it, and DOM assertions see nothing.

The fix: the same pinned dist/ ships inside the marimo pip package under _static/. Repoint the bundle's CDN refs at those local assets, serve the result, and drive the pre-installed Chromium. No network, real render.

render.py (beside this file) does the whole dance — build a serve root from marimo's _static/ plus the bundle's CDN-rewritten HTML, serve it, screenshot:

# Get a bundle first if you don't have one: ./go export docs/gpt-sweep/report.py
#   -> .mini/exports/gpt-sweep/  (index.html + _assets/)
uv run --with playwright python .claude/skills/report-render/render.py \
    .mini/exports/gpt-sweep -o /tmp/report.png

Then Read the PNG. --suffix '?show-code=true' appends to the URL; --wait-text 'some heading' blocks until that text renders instead of a fixed timeout.

Asserting on behavior, not just looking

For toggles / visibility / layout logic, drive the DOM instead of screenshotting. render.py's _build_serve_root + _serve are the reusable core; swap the screenshot for Playwright queries. This is how the show-code default was pinned down (PR #22) — e.g. across ?show-code values:

page.goto(f"http://127.0.0.1:{port}/index.html?show-code=false")
page.wait_for_timeout(3500)
code_shown = page.evaluate("document.body.innerText.includes('import marimo')")
page.locator("[aria-haspopup=menu]").first.click()          # open the ⋮ menu
toggle = page.locator("[data-testid=notebook-action-show-code]").count()

Why it works / gotchas

• Run through the project env (uv run --with playwright), not uvx: the local _static/ assets are hash-named per marimo version, so they only match a bundle exported by the same marimo. uvx --with marimo would resolve some other version and every asset would 404.
• Two asset dirs, no collision: the runtime lives under assets/ (from _static/), the report's figures under _assets/ (leading underscore, from the bundle). render.py symlinks both into the serve root.
• Chromium is pre-installed at /opt/pw-browsers/chromium (override with PLAYWRIGHT_CHROMIUM); don't run playwright install.
• A missing favicon/font 404 is cosmetic — the app still renders.

This same repoint-CDN-to-_static trick is what a full offline/archival bundle would do at publish time; here it's just scoped to a throwaway render.