@sveltejs/kit/src/runtime/app/server/event.js

SvelteKit is the fastest way to build Svelte apps

/** @import { RequestEvent } from '@sveltejs/kit' */

/** @type {RequestEvent | null} */
let request_event = null;

/** @type {import('node:async_hooks').AsyncLocalStorage<RequestEvent | null>} */
let als;

import('node:async_hooks')
	.then((hooks) => (als = new hooks.AsyncLocalStorage()))
	.catch(() => {
		// can't use AsyncLocalStorage, but can still call getRequestEvent synchronously.
		// this isn't behind `supports` because it's basically just StackBlitz (i.e.
		// in-browser usage) that doesn't support it AFAICT
	});

/**
 * Returns the current `RequestEvent`. Can be used inside server hooks, server `load` functions, actions, and endpoints (and functions called by them).
 *
 * In environments without [`AsyncLocalStorage`](https://nodejs.org/api/async_context.html#class-asynclocalstorage), this must be called synchronously (i.e. not after an `await`).
 * @since 2.20.0
 */
export function getRequestEvent() {
	const event = request_event ?? als?.getStore();

	if (!event) {
		let message =
			'Can only read the current request event inside functions invoked during `handle`, such as server `load` functions, actions, endpoints, and other server hooks.';

		if (!als) {
			message +=
				' In environments without `AsyncLocalStorage`, the event must be read synchronously, not after an `await`.';
		}

		throw new Error(message);
	}

	return event;
}

/**
 * @template T
 * @param {RequestEvent | null} event
 * @param {() => T} fn
 */
export function with_event(event, fn) {
	try {
		request_event = event;
		return als ? als.run(event, fn) : fn();
	} finally {
		request_event = null;
	}
}