fix(adapter-cloudflare-workers): throws status 404 if KVError instanceof

[vicentematus]

Describe the problem

Fixes #9288. The bug occurs when deploying to Cloudflare Workers, where requests for non-existing assets result in a 500 internal error instead of a 404 error.

The Solution

Add a try-catch clause to handle the exception if the error is an instance of KVError from Cloudflare Workers it will change the error.status to 404 instead of the default 500 as described in the PR.

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Latest commit: 8907ece

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@sveltejs/adapter-cloudflare-workers	Minor

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[Rich-Harris]

Thanks for the PR. It's not totally clear to me what effect setting error.status = 404 is supposed to have — judging by https://github.com/cloudflare/kv-asset-handler#getassetfromkv we should be doing this instead:

async function get_asset_from_kv(req, env, context, map = mapRequestToAsset) {
	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 (err) {
-		if (err instanceof KVError) err.status = 404;
+		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 })
+		}

-		throw err;
	}
}

The code in this PR is somewhat simpler, but is that behaviour documented somewhere?

[vicentematus]

My bad, i was confused. Rich is right. I added the errors that are documented on the documentation of kv-asset-handler. Fixed.

[benmccann]

it feels like this might make it hard for people to figure out what the underlying error is

[vicentematus]

I cant see how to improve this out. Should it throw the error that it catches on the try catch clause🤔 ?

[eltigerchino]

closing this since the issue has been resolved. Completed by #4276