fix: correctly analyse exported endpoint methods during build

[eltigerchino]

fixes #10984

Previously, the endpoint metadata would never be populated as described in the issue. However, I think it was only used in the Vercel adapter to fire off some warning

kit/packages/adapter-vercel/index.js

Lines 562 to 593 in 20d2fe7

	/** For a route to be considered 'valid', it must be an API route with a GET handler */
	const valid_routes = builder.routes.filter((route) => route.api.methods.includes('GET'));
	/** @type {Array<string>} */
	const unmatched_paths = [];
	for (const cron of crons) {
	if (typeof cron !== 'object' || cron === null || !('path' in cron)) {
	continue;
	}
	const { path } = cron;
	if (typeof path !== 'string') {
	continue;
	}
	if (!valid_routes.some((route) => route.pattern.test(path))) {
	unmatched_paths.push(path);
	}
	}
	if (unmatched_paths.length) {
	builder.log.warn(
	'\nWarning: vercel.json defines cron tasks that use paths that do not correspond to an API route with a GET handler (ignore this if the request is handled in your `handle` hook):'
	);
	for (const path of unmatched_paths) {
	console.log(` - ${path}`);
	}
	console.log('');
	}

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:.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2145088

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Patch

Not sure what this means? Click here to learn what changesets are.

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

[benmccann]

would it be too hard to add a test for this one?

[eltigerchino]

I guess I wasn't sure how to set one up. I can try to see if I can add an analyse.spec.js maybe.

[benmccann]

Actually, I think this would be equivalent and shorter?

Suggested change

	} else if (mod.fallback && key === 'fallback') {
	} else if (key === 'fallback') {

[eltigerchino]

I guess it depends if we want to check the value of fallback for truthiness. Is there a case (or is it even possible) where someone conditionally assigns a request handler to it?
e.g., export const fallback = dev ? requestHandler : undefined;

[Rich-Harris]

However, I think it was only used in the Vercel adapter to fire off some warning

IIRC the history here is that the arc.codes adapter needed to know which methods existed on each route. It was complicated and no-one was actually using it so we stopped maintaining it long before SvelteKit went stable, but kept the metadata around. Not super valuable but probably not worth killing off either