`$page.state` is cleared when `invalidate` is invoked

[aradalvand]

Describe the problem

The new shallow routing feature is pretty useful, but one thing I've just stumbled into and was surprised by is the fact that calling invalidate or invalidateAll, in addition to re-running the load functions, also clears $page.state (that means it destroys any "shallow routes" that might've been set); and it doesn't create a new history entry either, which is extra weird, it means the current history entry will still remain associated with the $page.state prior to the invalidateAll call, but the $page.state itself will be empty; causing a mismatch.

This can be undesirable. Sometimes you only want to re-run the load functions, that's it, the $page.state being emptied could be an unpleasant side-effect.
If someone wants to clear the $page.state as well, they could do so by simply invoking pushState({}) right afterwards. There's no reason for invalidateAll to do that internally, while not allowing the developer to choose whether they want that or not.

Describe the proposed solution

Either change the default behavior (I suspect this wasn't actually thought through, but feel free to correct me), or if this was somehow intended, at least add an option to invalidate and invalidateAll that leaves decision about whether they want to preserve the page state or not up to the developer:

invalidateAll({
    preserveState: true
});

Alternatives considered

No workarounds I could come up with, at the moment. Which is a big bummer.

Importance

severe

Additional Information

No response