Port a web app

An existing web app is the best test of niso, and the quickest way to find out whether yours will run. You need its static build: the directory a vite build, expo export or similar produces.

1. Run it headless

target/release/niso-run --page dist/index.html --root dist --url http://localhost/ \
  --missing --max-ms 15000

--root serves the build at http://localhost/; --url puts the page at the route the app expects (a router may care). --max-ms gives its timers 15 seconds of page time, which is milliseconds of real time.

2. Read what’s missing

--missing prints every DOM interface member and global the app looked up that niso doesn’t have. Not all of them matter: apps feature-test a lot. The ones to look at first are those that appear right before an uncaught exception (niso-run prints it and exits 1) or an error boundary in the --dump output.

Bluesky’s web build is a worked example: it mounts on niso and stops in two error boundaries, one for element.scroll({ behavior: 'smooth' }) and one for IntersectionObserver (Bluesky).

3. Check what it looks like

--boxes prints where every element landed, and niso-iced --page shows it in a window. Compare with the same build in Chrome.

4. Report or fix

A gap is either a missing API (look it up in the Web API reference and the support table) or a bug in one that exists. For niso contributors, an app worth keeping goes into the app corpus with a driver for its core flow, and its findings go on its page under Real apps.