feat(forge): add derive cheatcode for mnemonics

[devanoneth]

Motivation

I want to live in a world where we can run forge script MyScript and not need to worry about sourcing environment variables or adding any flags, rather allowing the script to setup everything it needs in the script itself. I think this is more declarative and leads to better scripts.

Solution

Add a derive cheatcode which allows to derive private keys from a given mnemonic string or file path. I am adding this PR early, on its own it does not seem to do much, but I would also like to add a remember cheatcode which will add private keys to the current forge invocation so that you can later broadcast with them.

It would allow for scripts such as the following:

Solenv.config();

uint256 deployerPrivateKey = vm.derive(vm.envString("MNEMONIC"), 0);
address deployer = vm.remember(deployerPrivateKey);

uint256 governancePrivateKey = vm.derive(vm.envString("MNEMONIC"), 1);
address governance = vm.remember(governancePrivateKey);

vm.startBroadcast(deployer);
Contract contract = new Contract(governance);
vm.stopBroadcast();

vm.startBroadcast(governance);
contract.addPair(vm.envString("PAIR"));
vm.stopBroadcast();

So, before I add the remember cheatcode I'd like to get feedback on this early. :) Thanks!

[mattsse]

great, ty!

lgtm, just a suggestion re naming

[mattsse]

I'd like to be a bit more explicit here about the naming,

wdyt of deriveKey?

[devanoneth]

Sure that works for me, just updated in the my last commit

[mattsse]

but I would also like to add a remember cheatcode which will add private keys to the current forge invocation

this would be possible, there is now a Context container type in Cheatcodes that's intended for this, for example that's where we currently store file handles for the file related cheatcodes

[mattsse]

lgtm, needs lint

any objections @gakonst @onbjerg ?

it'd be great if you could add a reference entry to the book as well

[devanoneth]

Oops, my bad on missing the last lint! Yes, re the book I plan to get the remember cheatcode in too ASAP and then will add both of them to the book.

[joshieDo]

i'd rather not assume that the path ends in a /

[devanoneth]

I originally wanted to do that, but changed it to fit in line more with ethers-rs.

With that said, I actually think I made it worse lol.

I'd be fine to add in the / for the path so that the user is not expected to. We could also hold the users hand and check for it and only add it if it's not there.

[joshieDo]

In that case, the path is a const and not a user input though...

We could also hold the users hand and check for it and only add it if it's not there.

I like it

[gakonst]

love the principle of making scripts as declarative as possible.

merging so we close the feedback loop and 👍 on trying to make the path derivation more robust, doubt people will add too many custom paths though