• (you can mark them as construction to keep them as-is, but you still have to replace the coincident constraints on the endpoints. And I didn't even know you could do this until I looked through the code)

This is documented here https://solvespace.com/ref.pl#Splitting in the last paragraph but it is not one of the "discoverable" features :-)

Writing from a phone, my inclination would be to perhaps keep the extra coincident constraints you added, but leave the construction behaviour as it is. Of course the new coincident constraints will be created only if both entities are already construction (and thus kept). I'll look into it from a PC.

Seems to work as advertised. I fear people might expect the new entities to follow the old construction ones the way it works when a point is turned into an arc, but that's non-trivial to make happen. OTOH people hit the like in this PR which doesn't happen very often ;-)

What do you think @ruevs?

I agree with @ruevs that even if old entities aren't kept by default, they should at least keep their endpoint constraints. (I still think they should be kept by default, but at least then it's two clicks and a keypress either way)

It seems to work to just do this if you want to keep the old behavior, and let whatever code deletes the old entities remove the redundant constraints when the entities aren't kept?

I need to play with this a little bit when I find some time. I'll try both variants. For now I can not give an opinion. The "pile of construction entities" after multiple splits worries me somewhat.

@jkrei0 @phkahler I tried both. Definitely https://github.com/jkrei0/solvespace/tree/constrain-split-entities for me.

The "piling" construction entities (when I did not intentionally do them) that this one creates truly bothers me.

• New entities are constrained to the endpoints of the old ones, but not constrained to them at the point where they meet. I would have tried to add this except for that there's no "point on spline" constraint, which would mean that only some parts could be constrained.

Also this is not at all a problem at all in my opinion. Having the ends of the newly split entities is in many cases desirable. And it is much easier to add points coincident constraints than to remove them.

It seems the constraints only version has a bug :(
If you create a spline, click so the end point is on the start point (so it makes a loop), then try to split it with a line, it crashes.
This doesn't happen with the version that always keeps entities, nor does it happen with solvespace w/o any of these changes.

Not sure why, and I can't get a debug report for some reason (nor can I get a debugger to work)?