fix: return updated layout data if child uses parent

[eltigerchino]

fixes #9355

This PR changes the server data to return the updated layout data from a layout node if a child load function uses parent. Previously, the child load function would receive the updated data from parent, but the layout node would still return the stale data.

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[dummdidumm]

I don't know how I feel about changing this. If the parent load function does not have anything in it that makes it officially rerun, I don't think we should let it rerun indirectly via await parent(). If await parent() happens to create new data then that's more of a misuse of the parent load function. We only need to re-request the parent data on the server because there's no way to pass the parent data back into the load function endpoint when we call it, so the parent knowledge has to be re-constructed. On the client that's not the case with the universal loaders, so it would make a confusing difference.

[eltigerchino]

We only need to re-request the parent data on the server because there's no way to pass the parent data back into the load function endpoint when we call it, so the parent knowledge has to be re-constructed.

Should we try to pursue some form of this (passing the parent data from the client to the server) so that the parent data is consistent?

If await parent() happens to create new data then that's more of a misuse of the parent load function.

There could also be cases where it isn't a misuse. For example: an admin updates a user's settings, causing the parent load function to return new data when the parent data is reconstructed. This would cause the layout data to be stale while the child load uses fresh data.

[dslatkin]

I don't know how I feel about changing this. If the parent load function does not have anything in it that makes it officially rerun, I don't think we should let it rerun indirectly via await parent().

If parent load functions do not rerun on await parent(), wouldn't that introduce a security issue for what several people are suggesting (and presumably doing) with it in #6315? A lot of people describe it as a viable way to ensure layouts that perform auth always rerun their load functions (and auth checks), particularly on page navs between routes that both fall under the same layout when the load function wouldn't otherwise rerun.

[dummdidumm]

You need to ensure that your layout reruns on every page change (by for example depending on the url) then it's safe - that issue is largely unrelated to this one

[dslatkin]

Ah I see, that makes sense, thanks, sorry for the confusion. Basically the rerun is to make sure an auth check happens in the first place (which can otherwise throw a 403 or something if it fails) and any awaiting of parents is to make sure the data from that auth check is available to a child load function that might need it