Initial store value is undefined for param with defaultValue set

[dominikg]

Describe the bug

creating a store and immediately accessing it in the root layout while defining a parameter with a default value causes the initial value to be undefined.

In the reproduction, there is a parameter "foo" with default "bar". accessing /, the url is updated to include ?foo=bar but the initial value in +layout.svelte is undefined.

This is unexpected and causes an error if you want to access $params.foo.

Possible solutions:

• Do not render default values in the url, but reflect them in the store if the url does not set a different value
• Fall back to default value if url does not supply it

Reproduction

https://www.sveltelab.dev/49is8k7v2xv3ap3

Logs

No response

[ollema]

maybe this is a separate feature request, but I think it would be really cool to not include default values in the URL at all. not upon initial page load, but also if they for some reason were set to their default value again in follow up page interactions.

the use case for this is a complex data table where there are lots of potential search params such as search filter params (q=), pagination params (page=,pageSize=), what columns to show (columns=)...

in those cases, it can be nice to show a clean URL if no filters actually have been applied. then that URL is easier to share. but if you for some reason have selected for example page 2 but then navigated to page 1 (which is the default), it would be nice if page 1 was pruned from the URL again so it is again easy to share

[paoloricciuti]

I'm a bit thorned about this, I want to think about the consequences of this. For example if you are reading from the load function without using the library it might be confusing. One of my ideas was to always reflect the url but I can see where having a default might help. I have to think about it