Commits on Nov 22, 2024

1. Simulated Token Balances for Verified Quotes …

   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 the
   **solver's** token balance for the simulation. The solver can then use
   this balance to top up the trader's account if needed (in the case were
   we allow mocking preconditions in the simulation - currently this is
   determined by whether or not the quote has hooks). We intentionally do
   not override the trader's balance in order to not interfere with hook
   execution in verified quotes.
   
   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.

   

   nlordell committed Nov 22, 2024
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