fix: throw known errors such as MethodNotAllowed, NotFoundError instead of 404 for kv assets

Author: vicentematus

.changeset/cool-foxes-battle.md

@@ -0,0 +1,4 @@
+---
+'@sveltejs/adapter-cloudflare-workers': minor
+---
+return known errors for non-existent asset rather than throwing KVError

packages/adapter-cloudflare-workers/files/entry.js

@@ -1,7 +1,12 @@
-import { Server } from 'SERVER';
-import { manifest, prerendered } from 'MANIFEST';
-import { getAssetFromKV, mapRequestToAsset } from '@cloudflare/kv-asset-handler';
-import static_asset_manifest_json from '__STATIC_CONTENT_MANIFEST';
+import { Server } from "SERVER";
+import { manifest, prerendered } from "MANIFEST";
+import {
+	getAssetFromKV,
+	mapRequestToAsset,
+	MethodNotAllowedError,
+	NotFoundError,
+} from "@cloudflare/kv-asset-handler";
+import static_asset_manifest_json from "__STATIC_CONTENT_MANIFEST";
 const static_asset_manifest = JSON.parse(static_asset_manifest_json);
 
 const server = new Server(manifest);
@@ -25,23 +30,23 @@ export default {
 			const res = await get_asset_from_kv(req, env, context);
 			if (is_error(res.status)) return res;
 
-			const cache_control = url.pathname.startsWith(app_path + 'immutable/')
-				? 'public, immutable, max-age=31536000'
-				: 'no-cache';
+			const cache_control = url.pathname.startsWith(app_path + "immutable/")
+				? "public, immutable, max-age=31536000"
+				: "no-cache";
 
 			return new Response(res.body, {
 				headers: {
 					// include original headers, minus cache-control which
 					// is overridden, and etag which is no longer useful
-					'cache-control': cache_control,
-					'content-type': res.headers.get('content-type'),
-					'x-robots-tag': 'noindex'
-				}
+					"cache-control": cache_control,
+					"content-type": res.headers.get("content-type"),
+					"x-robots-tag": "noindex",
+				},
 			});
 		}
 
 		// prerendered pages and index.html files
-		const pathname = url.pathname.replace(/\/$/, '');
+		const pathname = url.pathname.replace(/\/$/, "");
 		let file = pathname.substring(1);
 
 		try {
@@ -52,12 +57,12 @@ export default {
 
 		if (
 			manifest.assets.has(file) ||
-			manifest.assets.has(file + '/index.html') ||
-			prerendered.has(pathname || '/')
+			manifest.assets.has(file + "/index.html") ||
+			prerendered.has(pathname || "/")
 		) {
 			return get_asset_from_kv(req, env, context, (request, options) => {
-				if (prerendered.has(pathname || '/')) {
-					url.pathname = '/' + prerendered.get(pathname || '/').file;
+				if (prerendered.has(pathname || "/")) {
+					url.pathname = "/" + prerendered.get(pathname || "/").file;
 					return new Request(url.toString(), request);
 				}
 
@@ -71,13 +76,13 @@ export default {
 				env,
 				context,
 				// @ts-expect-error lib.dom is interfering with workers-types
-				caches
+				caches,
 			},
 			getClientAddress() {
-				return req.headers.get('cf-connecting-ip');
-			}
+				return req.headers.get("cf-connecting-ip");
+			},
 		});
-	}
+	},
 };
 
 /**
@@ -86,19 +91,29 @@ export default {
  * @param {any} context
  */
 async function get_asset_from_kv(req, env, context, map = mapRequestToAsset) {
-	return await getAssetFromKV(
-		{
-			request: req,
-			waitUntil(promise) {
-				return context.waitUntil(promise);
-			}
-		},
-		{
-			ASSET_NAMESPACE: env.__STATIC_CONTENT,
-			ASSET_MANIFEST: static_asset_manifest,
-			mapRequestToAsset: map
+	try {
+		return await getAssetFromKV(
+			{
+				request: req,
+				waitUntil(promise) {
+					return context.waitUntil(promise);
+				},
+			},
+			{
+				ASSET_NAMESPACE: env.__STATIC_CONTENT,
+				ASSET_MANIFEST: static_asset_manifest,
+				mapRequestToAsset: map,
+			},
+		);
+	} catch (e) {
+		if (e instanceof NotFoundError) {
+			return new Response("Not found", { status: 404 });
+		} else if (e instanceof MethodNotAllowedError) {
+			return new Response("Method not allowed", { status: 405 });
+		} else {
+			return new Response("Internal Error", { status: 500 });
 		}
-	);
+	}
 }
 
 /**