SvelteKit `page` store updates after component

[edgy-sphere]

Describe the bug

Background

I would like to have easy-to-use search filters for an item collection. To allow for bookmarking and opening in a new tab, a suggested filter should just be a link with the corresponding filter added to the URL search params.

Issue

This involves reading the current search params and per suggested filter creating a link, adding a search param to it. Using the page store directly in a component's script does not work properly, but appears to "lag behind" one page, presumably due to the page store being updated only after the component update/render. This only applies for links to the same path—see at path /fixed the link TEST HOME "year=2019", which works as intended; presumably because no components are reused.

Reproduction

Repo link: https://github.com/edgy-sphere/sveltekit-page-store-updates-after-component

• Clone: git clone https://github.com/edgy-sphere/sveltekit-page-store-updates-after-component.git
• Install dependencies: npm i
• Start the dev server: npm run dev
• Visit localhost:5173 in a contemporary browser.

Case A

(on path /) click e.g. on Parasite's year 2019, then the director links for both Parasite and 1917 only include the respective director instead of also including year=2019 in their search params. Clicking the Test Director button logs the correct link to everyone's favourite, the developer console.

Case B

Following Case A (not using the same URL, e.g. /?year=2019, instead you must navigate there from home /), click on HOME, then the links of the first two movies erroneously include year=2019 as well—not the next four, I guess because the corresponding components of these are created, while the components of the first two are reused.

Logs

No response

System Info

System:
    OS: Windows 11 10.0.22621
    CPU: (4) x64 Intel(R) Core(TM) i5-6600K CPU @ 3.50GHz
    Memory: 24.65 GB / 31.95 GB
Binaries:
    Node: 20.3.1 - C:\Portable\node\node.EXE
    npm: 9.6.7 - C:\Portable\node\npm.CMD
Browsers:
    Edge: Chromium (120.0.2210.91)
    Internet Explorer: 11.0.22621.1
npmPackages:
    @sveltejs/adapter-auto: ^3.0.0 => 3.0.1 
    @sveltejs/kit: ^2.0.0 => 2.0.6 
    @sveltejs/vite-plugin-svelte: ^3.0.0 => 3.0.1 
    svelte: ^4.2.7 => 4.2.8 
    vite: ^5.0.3 => 5.0.10

Severity

annoyance

Additional Information

Similar issues

• #11046
• #11417 ?

Workaround

When providing the page store as an argument to hrefFilter(...) (at movie.svelte) and not using it directly, all works as expected—see at path /fixed.

Solution

Updating the page store before the component seems (to me) more reasonable, as components may rely on the page store while not vice versa.

While a simple workaround exists, it may not be immediately obvious to everyone. In any case, this issue hopefully will provide some help.

Please apologise that I am not providing any practical help toward fixing this, as I am not sure whether this actually works as intended, could not quite understand how components are reused, and since my mediocre coding skills compared to my Git proficiency appear like I am expert-master of the universe.

[chriswep]

i'm seeing the same issue that everything in $page is "lagging behind", i.e. on page initialisation it still contains the data from the last route. However when accessed within onMount the data is correct. This is when using Svelte 5. With Svelte 4 $page has the correct data even outside onMount. Is this intended behaviour with Svelte 5? This would be unfortunate since it makes the code more complex. I assume $page.route.id and $page.params should be known even outside of onMount.

[gterras]

After upgrading to SvelteKit2 I'm seeing this behavior on a Svelte4-only project. I will try to find the time to provide a reproduction.

Edit: after further testing it looks like $page is not really "lagging behind" but rather two versions of $page (the old and the new) can exist at the same time (can switch from one to the other by navigating), I don't know if this is conceptually the same thing or not.

[madeleineostoja]

Edit: after further testing it looks like $page is not really "lagging behind" but rather two versions of $page (the old and the new) can exist at the same time (can switch from one to the other by navigating)

I can confirm that I think I'm seeing this behaviour (with svelte 4) as well — when I invalidate my load function that puts data into page, it updates as expected. When navigating to a new route it seems to revert back to the previous value of page, but if I get the data in the route it's correct

[teemingc]

I've tested this with Svelte 5 and it fixes the issue. I'm not sure if this is something we can fix in Kit itself (without notifying the page store twice). I'll close this issue but would like to know what others think. cc: @benmccann @dummdidumm