fix: fallback frame when navigating

[rigor789]

This handles a case where a frame with a different id might have overridden the previous frame with the same id, but has been unmounted.

/cc @farfromrefug

[farfromrefug]

i am not sure i understand. if no options.frame is passed and there is no more frame with id default in n-vue frame cache (because there are actually 2 frames with id default and one was removed) then there is no fallback to Frame.topmost()?

[rigor789]

getFrame(id) returns a frame from the frame Map - which is set/unset in the <Frame> component mounted/destroyed callbacks.

So when we destroy the 2nd default frame it's unset from the Map - but then $navigateTo is called, and by default the frame option is set to default, so it ends up using Frame.getFrameById('default') which returns the remaining Frame<default> that we pass as a fallback to getFrame(id, fallback) -> which then adds it back to the frame Map and returns it's vue VM instance... Essentially restoring it's entry to the frame Map.

It's a bit weird how we handle this, and the reason we even have the frame Map is because core will only return the frame from getFrameById if it has been navigated at least once... Perhaps it would make sense to patch that in core at some point and then refactor this whole setup to not rely on the frame Map.

[farfromrefug]

@rigor789 thanks for the explanation. I get it now! seems good to me