$page.url.pathname is inconsistent when using paths.base

[UnlimitedBytes]

Describe the bug

While writing the reproduction for #10124 I discovered another bug in SvelteKit. When you set the paths.base inside svelte.config.js the app/stores's $page.url becomes inconsistent. When initially calling the base like http://example.com/base it will redirect your browser to http://example.com/base/ and $page.url will be set to that too. Anyway as soon as hydration kicks in the $page.url will be set to http://example.com/base even if the browser url bar still shows http://example.com/base/. As far as I can tell this behavior is only present at the root of the base. Sub Routes like http://example.com/base/about are always redirected to the none slash version and therefore don't seem to have this bug.

Reproduction

Repository showcasing the bug in code: https://github.com/UnlimitedBytes/sveltekit-paths-base-bug
Because of the speed at which the hydration process happens it's very hard to see the change in $page.url by just looking at the current value. So I recommend you open up the source code viewer for the page and search for URL of the current site:. This will take you directly to the $page.url which is outputted. You can then see that the URL in the HTML source code ends with a slash while the URL displayed on the page (after hydration) doesn't contain an ending slash.

Logs

Not needed.

System Info

Not needed.

Severity

annoyance

Additional Information

Not needed.

[ghostdevv]

Possible duplicate/related to #9595