Strange sequence of calling lifecycle functions (beforeUpdate)

[a3con]

Continuing issues #2281. When rendering a list of nested components (A, B, C) and calling beforeUpdate, onMount, afterUpdate in each of them, all beforeUpdate calls occur first and in reverse order (I think this is unintuitive). Calls onMount and afterUpdate are predictable.

Here's a repro: https://svelte.dev/repl/0e2b1e068bb9431fa9f5e2827b552ff3?version=3.6.4

[antony]

This would be a breaking change to modify now, but I think from my point of view at least it makes sense. My reasoning is that beforeUpdate isn't part of the render lifecycle, and is called after the component is loaded, but before any state exists/changes. onMount is then called as the components mount in the DOM, and then afterUpdate is called because the state is modified as part of the component's mount sequence.

I think it's one of those things that would benefit from documentation, but is probably working in the intended way.