feat: implement adapter.emulate

[Rich-Harris]

Breaking this out of #11730, as the changes to adapter-cloudflare and adapter-cloudflare-workers are blocked on the next release of wrangler. Without it, we'll have to make platform.caches optional, which would be an annoying breaking change

(Actually, I've just realised that this technically only applies to adapter-cloudflare-workers, since context and caches are already optional in adapter-cloudflare for some reason. But it would be nice to support these in both.)

---

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with pnpm test and lint the project with pnpm lint and pnpm check

Changesets

• If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpm changeset and following the prompts. Changesets that add features should be minor and those that fix bugs should be patch. Please prefix changeset messages with feat:, fix:, or chore:.

Edits

• Please ensure that 'Allow edits from maintainers' is checked. PRs without this option may be closed.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 62b9db2

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[Rich-Harris]

TODO #11730 (comment)

[OJFord]

wrangler@3.25.0 was released yesterday with a miniflare bump, is that the one we're waiting for?

[hrueger]

I think we're waiting for cloudflare/workers-sdk#4847

[OJFord]

That's landed in 3.26.0, which is available (pre-release) at https://prerelease-registry.devprod.cloudflare.dev/workers-sdk/runs/7714710243/npm-package-wrangler-4854

I might try to work out how later anyway, but if it's of any help at all I'd be happy to give it a go to test.

[dario-piotrowicz]

wrangler 3.26.0 (with the no-op caches implementation) has just been released 🙂

[OJFord]

I might try to work out how later anyway, but if it's of any help at all I'd be happy to give it a go to test.

I updated my dependencies to:

    "@sveltejs/adapter-cloudflare": "file:../kit/packages/adapter-cloudflare",
    "@sveltejs/kit": "^2.4.3",
    "wrangler": "^3.26.0",

cloned gh:sveltejs/kit --depth=1 --branch=cloudflare-adapter-dev, and ran:

../kit$yay -Sy pnpm # (install pnpm, whatever package manager)
../kit$pnpm install
../kit$pnpm build

removed my if-dev-then-miniflare hacks, and... it seems to be working fine - I'm only using D1 at the moment, but it seems to work exactly as promised; the only local-conditional stuff I have now is to make Drizzle play ball.

Thanks!

[ottomated]

Is there anything blocking this at the moment? This would be a huge win for my productivity :)

[eltigerchino]

@dario-piotrowicz @Rich-Harris is there anything else that needs to be done in this PR? Or does it look good enough after updating to the latest wrangler version and passing in the proxy properties to emulate?

[dario-piotrowicz]

@dario-piotrowicz @Rich-Harris is there anything else that needs to be done in this PR? Or does it look good enough after updating to the latest wrangler version and passing in the proxy properties to emulate?

I think it looks great! 😄
(with your suggestions applied that is)

From my point of view it looks good and could be shipped 🙂, we can always iterate and improve things if the need arises

[benmccann]

Type checking is currently failing because some required fields on platform are not defined in adapter-cloudflare-workers. I notice these fields are are required in adapter-cloudflare-workers/ambient.d.ts and not in adapter-cloudflare/ambient.d.ts, which is why it's only the adapter-cloudflare-workers build that's failing. I'm not familiar enough with this functionality to know if we want those fields to be required or not, but it seems like we should align them

[eltigerchino]

I think it would make sense to make all of the properties non-optional since they're now provided during dev and build. They should be provided during prerendering as well, but throw an error similar to how we handle accessing env during prerendering in this PR. Should these type changes be made in a separate PR?

ambient.d.ts

import { CacheStorage, IncomingRequestCfProperties } from '@cloudflare/workers-types';

declare global {
	namespace App {
		export interface Platform {
+			/**
+			 * Lifecycle methods to augment or control how the request is handled.
+			 */
-			context?: {
+			context: {
+				/**
+				 * Executes a promised-based task before the handler terminates but without blocking the response.
+				 * 
+				 * See the [official docs](https://developers.cloudflare.com/workers/runtime-apis/handlers/fetch/#contextwaituntil).
+				 * 
+				 * @param promise
+				 */
				waitUntil(promise: Promise<any>): void;
			};
+			/**
+			 * The Cache API allows fine grained control of reading and writing from the Cloudflare global network cache.
+			 * 
+			 * See the [official docs](https://developers.cloudflare.com/workers/runtime-apis/cache/).
+			 */
-			caches?: CacheStorage;
+			caches: CacheStorage;
+			/**
+			 * An object containing properties about the incoming request provided by Cloudflare’s global network.
+			 * 
+			 * See the [official docs](https://developers.cloudflare.com/workers/runtime-apis/request/#incomingrequestcfproperties).
+			 */
-			cf?: IncomingRequestCfProperties;	
+			cf: IncomingRequestCfProperties;	
		}
	}
}

The only issue is that they're not available during preview (but we want that to proxy to the wrangler command where they are available). Otherwise, making them all optional would be a breaking change for adapter-cloudflare-workers no?