createAppHandler() — astro Function Reference

Architecture documentation for the createAppHandler() function in serve-app.ts from the astro codebase.

Function typescript CoreAstro CoreMiddleware

Entity Profile

CoreAstro→ CoreMiddleware→ createAppHandler() — astro Function Reference

Dependency Diagram

graph TD
  8323d38f_c948_9920_2eff_297399c26640["createAppHandler()"]
  5b6342d4_34c1_b338_e76a_caf786fff1fb["serve-app.ts"]
  8323d38f_c948_9920_2eff_297399c26640 -->|defined in| 5b6342d4_34c1_b338_e76a_caf786fff1fb
  style 8323d38f_c948_9920_2eff_297399c26640 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

packages/integrations/node/src/serve-app.ts lines 10–71

export function createAppHandler(app: NodeApp, options: Options): RequestHandler {
	/**
	 * Keep track of the current request path using AsyncLocalStorage.
	 * Used to log unhandled rejections with a helpful message.
	 */
	const als = new AsyncLocalStorage<string>();
	const logger = app.getAdapterLogger();
	process.on('unhandledRejection', (reason) => {
		const requestUrl = als.getStore();
		logger.error(`Unhandled rejection while rendering ${requestUrl}`);
		console.error(reason);
	});

	const originUrl = options.experimentalErrorPageHost
		? new URL(options.experimentalErrorPageHost)
		: undefined;

	const prerenderedErrorPageFetch = originUrl
		? (url: string) => {
				const errorPageUrl = new URL(url);
				errorPageUrl.protocol = originUrl.protocol;
				errorPageUrl.host = originUrl.host;
				return fetch(errorPageUrl);
			}
		: undefined;

	return async (req, res, next, locals) => {
		let request: Request;
		try {
			request = NodeApp.createRequest(req, {
				allowedDomains: app.getAllowedDomains?.() ?? [],
			});
		} catch (err) {
			logger.error(`Could not render ${req.url}`);
			console.error(err);
			res.statusCode = 500;
			res.end('Internal Server Error');
			return;
		}

		// Redirects are considered prerendered routes in static mode, but we want to
		// handle them dynamically, so prerendered routes are included here.
		const routeData = app.match(request, true);
		// But we still want to skip prerendered pages.
		if (routeData && !(routeData.type === 'page' && routeData.prerender)) {
			const response = await als.run(request.url, () =>
				app.render(request, {
					addCookieHeader: true,
					locals,
					routeData,
					prerenderedErrorPageFetch,
				}),
			);
			await NodeApp.writeResponse(response, res);
		} else if (next) {
			return next();
		} else {
			const response = await app.render(req, { addCookieHeader: true, prerenderedErrorPageFetch });
			await NodeApp.writeResponse(response, res);
		}
	};
}