PoC for Safe simulateTransaction function

[mshakeg]

This PR introduces a new function, simulateTransaction, to the Safe contract, allowing users to simulate transactions without requiring the threshold of owner signatures. The simulation helps estimate gas usage and verify if a transaction would succeed without actually executing it, thus providing a reliable method for pre-execution checks.

Fixes #788

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[mshakeg]

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[mshakeg]

recheck

[mmv08]

Hey, thank you for the contribution. this can be an external contract used through

safe-smart-account/contracts/common/StorageAccessible.sol

Line 42 in 8f80a83

function simulateAndRevert(address targetContract, bytes memory calldataPayload) external {

. We're quite short on the bytecode size, so I'm almost sure we will not include this in the core contract.

[mshakeg]

@mmv08 thanks, so I took a look at linked StorageAccessible. simulateAndRevert section of code and what from I can tell it should work something like:

1. say I've got a safeTx that I want to simulate on safe where the safeTx is to, value, data and operation
2. now I can simulate the above safeTx but I don't have any owner signatures
3. so I call safe.simulateAndRevert(targetContract, calldataPayload)
   • targetContract: this will be the SimulateTxAccessor address
   • calldataPayload: this will be the encoded bytes of SimulateTxAccessor.simulate(to, value, data, operation)
4. now success can be extracted from the revert message

Is this understanding correct? And if so, does the ts sdk expose a function to do this simulation? Also, since it reverts eth_estimateGas wouldn't return the gasUsed for the simulation safeTx, so that seems to be a deficiency with this method.

[mshakeg]

@mmv08 I added the gasUsed to the revert data. It seems to work fine for most txs, however the simulations for txs that transfer the native asset all fail:

npx hardhat test test/core/Safe.Execution.spec.ts

[mmv08]

@mmv08 thanks, so I took a look at linked StorageAccessible. simulateAndRevert section of code and what from I can tell it should work something like:

1. say I've got a safeTx that I want to simulate on safe where the safeTx is to, value, data and operation

2. now I can simulate the above safeTx but I don't have any owner signatures

3. so I call safe.simulateAndRevert(targetContract, calldataPayload)

   • targetContract: this will be the SimulateTxAccessor address
   • calldataPayload: this will be the encoded bytes of SimulateTxAccessor.simulate(to, value, data, operation)

4. now success can be extracted from the revert message

Is this understanding correct? And if so, does the ts sdk expose a function to do this simulation? Also, since it reverts eth_estimateGas wouldn't return the gasUsed for the simulation safeTx, so that seems to be a deficiency with this method.

You can make a library that contains a function similar to your original simulateTransaction method, have this function return whatever you want and then use the return data from there. There are no code changes required in the safe core contract to achieve the functionality you're suggesting

[mmv08]

This can be returned by the targetContract. You can check the SimulateTxAccessor contract for an example. You can basically combine its approach with your original contract for detailed simulations

[mshakeg]

@mmv08 agreed, no changes are required to core, but does safe-global have a repo with periphery contracts? seems like this functionality would be quite essential to gas estimation and should be included in the sdk(and so would require leveraging a safe deployed contract).

[davidaucoin7377]

Simulation

[mshakeg]

this is redundant since SimulateTxAccessor.simulate returndata includes the safeTxGas:

(uint256 estimate, bool success, bytes memory returnData)