astro/dist/core/app/prerender.js

Astro is a modern site builder with web best practices, performance, and DX front-of-mind.

import { getEnvironment, setEnvironment } from "../environment/index.js";
import { collectPrerenderMetadata } from "../render-scope/collect.js";
/**
* Makes render errors fail the prerender instead of rendering a 500 page.
*
* Adapter runtimes that prerender with a production app (e.g. the Cloudflare
* prerender worker) default to the production error strategy, which turns a
* render error into a 500 page. Requests handled by the app itself can be
* intercepted through `app.renderError`, but requests handled by a user-provided
* `src/fetch.ts` (`astro(new FetchState(request))`) resolve the error strategy
* from the manifest's environment, so it must be switched there too. Otherwise
* the error is swallowed and an empty page is written to disk.
*
* Only the production (`default`) strategy is replaced; dev and build
* environments already have the right behavior.
*/
function useBuildErrorStrategy(manifest) {
	const env = getEnvironment(manifest);
	if (env.errorStrategy === "default") {
		setEnvironment(manifest, {
			...env,
			errorStrategy: "build"
		});
	}
}
/** Statuses the `Response` constructor rejects a body for. */
const NULL_BODY_STATUSES = [
	101,
	204,
	205,
	304
];
/**
* Renders a single prerendered path through `app.render`, collecting the
* per-render metadata (content entries rendered, image transforms resolved)
* and returning it by value on the result.
*
* The response body is fully buffered *inside* the render scope so
* lazily-driven rendering work records before the metadata snapshot; the
* returned response is a reconstruction carrying the buffered body with
* status/statusText/headers and body-nullness preserved.
*
* This function performs no scope installation; installing a render scope for
* the rendering runtime is the caller's responsibility. When no scope is
* installed, `metadata` is `undefined` ("not tracked").
*/
export async function renderForPrerender(app, request, options) {
	if (app.manifest) {
		useBuildErrorStrategy(app.manifest);
	}
	const routeData = options?.routeData;
	const { value: response, metadata } = await collectPrerenderMetadata(async () => {
		const rendered = await app.render(request, { routeData });
		const bytes = rendered.body === null ? null : await rendered.arrayBuffer();
		const nullBody = bytes === null || NULL_BODY_STATUSES.includes(rendered.status);
		return new Response(nullBody ? null : bytes, {
			status: rendered.status,
			statusText: rendered.statusText,
			headers: rendered.headers
		});
	}, app.logger, { staticImages: options?.staticImages });
	return {
		response,
		metadata
	};
}