mergeProps

function mergeProps<T extends Record<string, any>>(...args: T[]): T;

Composes several prop objects into one, the way every official Zag adapter
does: on* handlers are chained (both run), class values are joined,
style values are deep-merged, and plain attributes follow last-wins.
Without it, spreading a prop getter and then writing a literal onClick
would replace Zag’s handler and silently break the machine.

import { mergeProps } from "marko-zag";

<button ...mergeProps(api().getTriggerProps(), {
  class: "btn",
  onClick() { console.log("runs first, then Zag's handler") },
})>

Behavior

• Handlers: for a key present in both objects, the later object’s
  handler runs first, then the earlier one’s (Zag’s convention). Marko’s
  extra handler argument (the element) is forwarded to every handler.
• class: values joined with a space.
• style: objects are merged; a CSS string style is parsed and merged
  too. The result is always an object with hyphenated keys
  (--custom-props untouched) — the shape Marko expects.
• Plain attributes: the later object wins; undefined never clobbers an
  earlier value.

Wraps @zag-js/core’s mergeProps (which also unions data-ownedby) and
re-normalizes the merged style for Marko.