0x Permit2 send it

[twblack88]

0x launched their new API. They sent us all this documentation about saving people gas and making the UX better. This ticket covers picking up a more secure pattern for token allowances on the 0x swapper.

It's basically: replace approval with permit2 for the 0x swapper.

Consider it low priority but worth picking up. Should only use the pattern for permit2 since we already have token-approval signature transaction flows (sign to approve) and then send the transaction. In our current app permit2 upgrades a current onchain siganture to an "offchain signature for limited approval and an onchain signature for the trade." Already better.

"If your integration doesn't support collecting offchain signatures, such as with smart contracts, we recommend using AllowanceHolder."

☝️ this is what we have to verify and account for.

from smart contract lore, a good overview: https://github.com/dragonfly-xyz/useful-solidity-patterns/tree/main/patterns/permit2

0x docs: https://0x.org/docs/upgrading/upgrading_to_swap_v2#step-1-get-indicative-price

Headless example: https://github.com/0xProject/0x-examples/blob/main/swap-v2-headless-example/index.ts#L62-L83

[twblack88]

@reallybeard it's simple and we already have this, but a mock or two here would be super helpful.

0x is nagging us about upgrading to v2 so we might as well see where we're going. Just to round it out.

[woodenfurniture]

Questions to answer:

• Can we wrap all of the swappers in Permit2 or does the protocol need to support Permit2 for it to work?

Contracts must be purposely written to support Permit2. We will have to support both flows.

[twblack88]

@woodenfurniture going for extra credit. @reallybeard gonna get mocks .

vomited thoughts for now https://excalidraw.com/#room=57937cdcd3d70f535ad4,MgzvO8mKR_lRaC18ncX2-g

[0xean]

waiting for UI help from @reallybeard

[reallybeard]

Was having trouble getting this to run correctly on my local env. But I went through the different jams. Everything looks great, only small feedback is to move the instructions below the label. @woodenfurniture

Crappy screenshot attached.