[fix] refactor navigation singletons to avoid storing undefined reference

[pixelmund]

This PR fixes #3269, once you import $app/navigation on multiple places inside your app and it's included inside chunks/vendor.js the router would be set before the init function is called and would always be undefined.

Current Bundle:

/// vendor-c70aba79.js
let router$1;
function init(opts) {
  router$1 = opts.router;
}
/// ....
const router = router$1; // Router is undefined and doesnt change on init call
const goto = goto_;
const invalidate = invalidate_;
async function goto_(href, opts) {
  return router.goto(href, opts, []);
}

New Bundle:

let router;
function init(opts) {
  router = opts.router;
}
const goto = goto_;
const invalidate = invalidate_;
async function goto_(href, opts) {
  return router.goto(href, opts, []);
}

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[pixelmund]

Don't know why the test is failing seems not related to this change.

[changeset-bot]

🦋 Changeset detected

Latest commit: 1b77e71

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

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[benmccann]

I don't understand how this PR changes anything. If the router is not present when init is called, won't that still be the case?

Also, I'm not sure if it helps, but Vite is removing the vendor chunk: vitejs/vite#6534

[pixelmund]

The router const is assigned with the undefined router$1 and the init call only reassigns the router$1 with the actual router. But the const router stays always undefined. This PR removes the const so the reassignment in init works as expected.

Maybe we don't even need this change if the vendor gets removed within vite.

[benmccann]

Ah, I see. No still seems like a good change to make even on top of the Vite change