Foundry does not create a new, clean EVM environment when the chainId is changed

[pcaversaccio]

Component

Forge

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

forge 0.2.0 (87283bc 2023-10-07T00:16:07.431446791Z)

What command(s) is the bug in?

forge test

Operating System

Linux

Describe the bug

Foundry does not create a new, clean EVM environment when the chainId is changed, and a deployment of a contract to the same address therefore fails. To solve this problem currently, I return to the original snapshot state.

Simple repro:

• CREATE2 deploy a contract
• Change chainId to an ID via vm.chainId that is not equal to the original chainId
• Redeploy via CREATE2
• Will revert due to EIP-684

[Evalir]

Hmm, this seems like expected behavior and not an issue? I understand there's a point to clean up the evm state if you change chain IDs, but, it severely overloads the chainId cheatcode. I'll close this for now but feel free to reopen if you think this should be discussed further. I can see how the current behavior is useful for simulation or CTF purposes

[pcaversaccio]

@Evalir fwiw, you should probably close this issue as Not Planned instead of Completed. The reason why such a feature is desirable to me is that in my CreateX tests I had to mock contract creation frontrunning and redeployment events on other chains, and snapshot reverts can become annoying. But maybe it's an edge case...