[presign] Add onchain cancelation of orders

[anxolin]

Description This issue is to implement onchain cancelation of orders.

Something to decide is:

• Should we implement it only for pre-sign use case? or should we do it also for EOA (and give users a choice)

Context

When implementing presign, we decided to remove temporarilly cancelation of orders, since we can't sign the offchain order as EOA do.

This issue, is just to reiterate and allow SC to cancel orders.

cc/ @biocom

[alfetopito]

I vote for onchain cancellation only for onchain orders.

I feel like it would confuse more than help most users to have 2 ways of cancelling EOAs.

We can iterate and add an "advanced" option later on if there's demand, but I wouldn't want to add it now.

[anxolin]

I vote for onchain cancellation only for onchain orders. I feel like it would confuse more than help most users to have 2 ways of cancelling EOAs. We can iterate and add an "advanced" option later on if there's demand, but I wouldn't want to add it now.

I'm also prefering that. Noone has expressed any concern with the other kind of cancelations. However, i left it open to hear if someone has more opinions.

[fairlighteth]

Here's my understanding:

• For EOA wallets, the soft cancellation seems to work until now, until reported issues proof otherwise. Based on that we could conclude it currently has a positive user experience. Alternatively, a more sophisticated user could override their nonce in a relatively quick way, if a on-chain cancellation was desired.
• For SC wallets the only option to cancel, is to do an on-chain cancellation. My understanding is, overriding the nonce in the SC will not work here, given the nonce is 'reserved' (???).

Conclusion:

• So for SC wallets, there's only a single 'cancellation' option available. Which is an on-chain transaction that needs to be executed. This is the current situation.
• For EOA wallets both could apply. If we provide both options, that can be confusing to someone who doesn't know the difference. To someone who does know the difference, it actually can be quite convenient to have such an option provided by the CowSwap UI (as opposed to rely on their client/wallet). Are there gas price differences between overriding the nonce on my end (e.g. send ETH to my own wallet) vs. executing a smart contract function to cancel? Otherwise, I'd consider this either an 'Expert mode' feature or something you can toggle on/off in your settings.

[stale[bot]]

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