Generate typed classes from a manifest

spaday’s typed component classes are generated from a Custom Elements Manifest (custom-elements.json) — the standard description web-component libraries publish. This guide shows you how to generate classes for any such library. (For a library that is not a web component, see Wrap an imperative library.)

Generate a committed module

For typed classes you check into your project, use the spaday-cem CLI or spaday.generate:

spaday-cem path/to/custom-elements.json -o my_components.py

import spaday

code = spaday.generate("custom-elements.json")   # returns the module source (typed classes)

This is how the built-in WebAwesome catalog is produced. A test checks the committed spaday/components/webawesome.py against its source manifest so it can’t silently drift; regenerate it with spaday-cem <manifest> -o spaday/components/webawesome.py followed by ruff format.

Build classes at runtime

For a one-off or experimental manifest, spaday.classes builds the classes in memory instead — no file, no static types, but it still validates keyword names:

import spaday

ns = spaday.classes("custom-elements.json")                    # {"WaSwitch": <class>, ...}
WaSwitch = spaday.classes("custom-elements.json", "WaSwitch")  # or one class by name
WaSwitch(checked=True).to_node()

One manifest, both bindings

The parse that produces the Python classes (spaday.parse_cem(), in the Rust core) also drives the JavaScript runtime’s registry — how each prop is set, which events to bind, the slot names. So a single manifest yields both the typed Python authoring API and the browser binding, with no chance of the two disagreeing.