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Add GovernorCountingFractional #5045

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Amxx
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@Amxx Amxx commented May 15, 2024

Fixes #4958

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  • Tests
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  • Changeset entry (run npx changeset add)

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🦋 Changeset detected

Latest commit: 149fe65

The changes in this PR will be included in the next version bump.

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@Amxx Amxx added this to the 5.1 milestone May 15, 2024
@Amxx Amxx requested review from ernestognw and frangio May 15, 2024 15:16
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Amxx commented May 15, 2024

12123b0 fixes the events, but is a breaking change. I don't think its a big deal (it wont be silent, compiler fail) ... but its not ideal.

@ernestognw @frangio WDYT?

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frangio commented May 15, 2024

I don't see a way to fix this without a breaking change. Another possible fix would be to add a new internal function. But I think just adding a return value is a better option.

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But I think just adding a return value is a better option.

Yeah same, it's one of those breaking changes that are easy to fix imo.

@Amxx Amxx requested a review from ernestognw May 16, 2024 15:45
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Almost there!

@ernestognw ernestognw changed the title GovernorCountingFractional Add GovernorCountingFractional May 24, 2024
* * Voting from an L2 with tokens held by a bridge
* * Voting privately from a shielded pool using zero knowledge proofs.
*
* Based on ScopeLift's GovernorCountingFractional[https://github.com/ScopeLift/flexible-voting/blob/e5de2efd1368387b840931f19f3c184c85842761/src/GovernorCountingFractional.sol]
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Are there any important differences that people should consider if they migrate from ScopeLift's implementation to this one, or if an interface has to support both? I think it may be worth listing them here.

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@ernestognw ernestognw May 29, 2024

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So far:

  • The reference implementation is in OpenZeppelin Contracts v4
  • It includes a nonce in the params object given v4 had no nonce protection
  • The COUNTING_MODDE is different

The voting format may vary after the reviews. I think it's currently fine since it reads it's "based on", so no compatibility should be assumed right away

return usedWeight;
}

function _extractUint128(bytes memory data, uint256 pos) private pure returns (uint128 result) {
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This function concerns me because the length of data is ignored and pos may be reading out of bounds. The assembly block correctly omits the memory-safe annotation, but like I said in a recent issue this globally disables optimizations so it should be avoided.

Is it possible to just check the validity of pos against the data length? Sadly I do see it would make the code less efficient by checking the length three times... Perhaps the helper should directly unpack all three parameters.

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I think having the helper to unpack all three parameters is the easiest to ensure memory safetyness.

I'll update with this alternative

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This is private, and everywhere we call it we first validate the length. Is that not good enough?

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GIven how frequent it is for people to copy-paste from our code I think we should try to make functions self-contained and well documented even if they're private.

In this case, not only that I think this is the cleanest way of making the assembly block memory-safe to avoid disabling optimizations, but also I share the concern with @frangio; although the function is unreachable with invalid parameters, I don't feel comfortable having such a function around.

ernestognw
ernestognw previously approved these changes May 29, 2024
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LGTM

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Amxx commented May 29, 2024

I honestly feel e0f5b71 reduces redeability ne consistency (instead of checking length in one place for both paths, we do it in two different places).

I don't understand what the issue is with having a private function that doesn't check the input validity if it is called with input that was already validated.

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I'd be open to change it as long as we either remove the assembly or make the block memory-safe.

I agree it's not an issue itself given the function is private and can't be reached with invalid arguments, it's just that I wouldn't feel comfortable given how people might use the code.

@Amxx Amxx force-pushed the feature/governor-counting-fractional branch from 3f1c13b to 37391ce Compare May 30, 2024 08:55
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frangio commented May 30, 2024

I think it would be ok to leave the previous _extractUint128 if we mark it as memory-safe, along with a comment warning that the caller must validate pos.

ernestognw
ernestognw previously approved these changes May 30, 2024
* potentially large number of calls to cast all their votes. The voter has the possibility to cast all the
* remaining votes in a single operation using the traditional "bravo" vote.
*/
// slither-disable-next-line cyclomatic-complexity
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For the record, we both feel fine by keeping this function self contained

// - "Fractional" voting: `support = 255`, with 48 bytes params.
if (support == uint8(GovernorCountingSimple.VoteType.Against)) {
if (params.length != 0) revert GovernorInvalidVoteParams();
usedWeight = againstVotes = remainingWeight;
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Similarly, we agreed that this double assignment is clear enough

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LFG 🚀

@ernestognw ernestognw merged commit c1d6ad5 into OpenZeppelin:master May 30, 2024
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@Amxx Amxx deleted the feature/governor-counting-fractional branch June 4, 2024 19:47
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Seeing as the main benefit of this is to allow for proxy voting of locked tokens, are there any plans on adding a FlexVotingClient like the one in ScopeLift that users can use with this governor? At the moment, I want to use this, but it seems like I will have to adapt the client from ScopeLift in order to make it work (after reviewing the diff from this and theirs).

I am unsure if I should open an issue for this.

https://github.com/ScopeLift/flexible-voting/blob/master/src/FlexVotingClient.sol

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Amxx commented Oct 14, 2024

I am unsure if I should open an issue for this.

Yes please, open an issue describing the behavior desired as precisely as possible.

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Add Flexible Voting to Governor
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