Settle Uniswap order in settle function along the ETH path

[gnosis]

Settle Uniswap order in settle function along the ETH path

[fleupold]

cc @josojo, @koeppelmann

Which price should the "clearing-price-range-assertion" be based on? The one of the direct Uniswap pool if existing (tokenA<>tokenB) or the price via ETH (tokenA<>ETH<>tokenB).

I think we initially suggested the latter, however since this increases the uniswap spread from 0.3 to 0.6 (two hops) I can see how users might feel betrayed if there exists a liquid direct pool (e.g. GNO<>OWL). Therefore, the second suggestion was to choose the "better" of the two.

For that, we have two cases

1. Settlement requires trade with Uniswap
2. Settlement doesn't require trade with Uniswap

In case 1) we could just assert that the clearing price is taken from whichever of the two pools offers the better price for settling the required amount.
The second case is slightly harder, since one pool could have a better spot price but a lot of slippage (making it look better but being worse for actual trading).

We could also chose which pool would give the better price for trading the cumulative sell amount and always use this one.

Either way the decision seems non-trivial.

[josojo]

In case 1) we could just assert that the clearing price is taken from whichever of the two pools offers the better price for settling the required amount.

agreed

The second case is slightly harder, since one pool could have a better spot price but a lot of slippage (making it look better but being worse for actual trading).

How about taking the spot price of the two-hop path, but still only allowing 0.3 spread. That seems reasonable to me, as we don't allow big slippage, but still, we take the price having the most liquidity in most cases.