Simulated Token Balances for Verified Quotes #3147
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This PR is a follow up to cowprotocol#3125 and uses the component introduced in the aforementioned PR for setting up a simulated token balance using state overrides in order for quote verification to work even when the trader does not have sufficient balance. The way it works is by configuring known mapping slots for the `mapping(address => uint256) balances` in ERC20 token contract implementations and using this to compute the slot for overriding a separate account's token balance (the `Spardose`), which can prefund the trader during quote simualtions. We intentionally do not override the trader's or solver's balance in order to not interfere with the settlement process: > Technically a solver could have private inventory they would like to > use for the solution instead of transfering it to the trader. _Posted by @MartinquaXD_ Note that the type of the state override changed slightly. This is because it was wrong to begin with. Node implementations I tested with (Geth and Anvil) expect both the slot and the value for state overrides to be exactly 32-bytes long (so `H256`). I guess this feature of the state override in the `ethrpc` crate was not used in the past and therefore no one noticed 🤷. ### Test Plan Added an E2E test that uses the new token balance override feature in order to produce a verified quote for a trader with no balances. Note that commenting out the API arguments causes the test to fail as expected.
This was referenced Dec 5, 2024
nlordell
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Dec 5, 2024
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This is just to silence a Solidity compiler warning.
MartinquaXD
approved these changes
Dec 5, 2024
sunce86
approved these changes
Dec 5, 2024
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Description
This PR is a follow up to #3125 and uses the component introduced in the aforementioned PR for setting up a simulated token balance using state overrides in order for quote verification to work even when the trader does not have sufficient balance.
Changes
The way it works is by configuring known mapping slots for the
mapping(address => uint256) balancesin ERC20 token contract implementations and using this to compute the slot for overriding a separate account's token balance (theSpardose), which can prefund the trader during quote simualtions. We intentionally do not override the trader's or solver's balance in order to not interfere with the settlement process:Posted by @MartinquaXD
Note that the type of the state override changed slightly. This is because it was wrong to begin with. Node implementations I tested with (Geth and Anvil) expect both the slot and the value for state overrides to be exactly 32-bytes long (so
H256). I guess this feature of the state override in theethrpccrate was not used in the past and therefore no one noticed 🤷.StateOverridetype and serializationTest Plan
Added an E2E test that uses the new token balance override feature in order to produce a verified quote for a trader with no balances. Note that commenting out the API arguments causes the test to fail as expected.