A slottable's assigned slot is never reset

[simonwuelker]

What is the issue with the DOM Standard?

When assigning slottables for a slot, the spec updates the assigned slot of any slottable that is added to the slot in

4. For each slottable of slottables, set slottable’s assigned slot to slot.

However, the assigned slot of any slottables that were previously assigned to the slot but aren't anymore won't change. I would expect a slottable's assigned slot to be null if that slottable is not also part of that slot's assigned nodes.

I'm not sure if this is intended, because the assignedSlot getter for slottables seems to work around it by calling find a slot.

This is causing extra work in algorithms like Node::remove:

If node is assigned, then run assign slottables for node’s assigned slot.

If the node was previously removed from a slot (but keeps a nonnull assigned slot) then this won't do anything.

[annevk]

I honestly don't quite recall why we (maybe just me) did it this way. I think a refactoring would be okay. Are you interested in working on that?

(@domenic, @hayatoito, or @smaug---- might remember more.)

[simonwuelker]

Are you interested in working on that?

Yeah sure! I'll wait a bit for the authors you pinged to give their thoughts (if any).

For reference, the version of assign slottables that I implemented in servo does disconnect slottables that are removed (doing so simplified the logic in the stylo integration) and so far that hasn't caused any problems for us.

https://github.com/servo/servo/blob/90130315a771cf2d52c982523721162f007a400c/components/script/dom/htmlslotelement.rs#L330-L337

[annevk]

It might be worth looking at blame for the original commit, though I somewhat doubt it will give much context.