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Delegate override vote (#5192)
Co-authored-by: Arr00 <[email protected]>
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‎.changeset/great-lions-hear.md

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---
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'openzeppelin-solidity': patch
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---
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`VotesExtended`: Create an extension of `Votes` which checkpoints balances and delegates.

‎.changeset/pink-wasps-hammer.md

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---
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'openzeppelin-solidity': patch
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---
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`GovernorCountingOverridable`: Add a governor counting module that enables token holders to override the vote of their delegate.

‎contracts/governance/Governor.sol

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@@ -260,6 +260,13 @@ abstract contract Governor is Context, ERC165, EIP712, Nonces, IGovernor, IERC72
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bytes memory params
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) internal virtual returns (uint256);
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263+
/**
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* @dev Hook that should be called every time the tally for a proposal is updated.
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*
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* Note: This function must run successfully. Reverts will result in the bricking of governance
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*/
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function _tallyUpdated(uint256 proposalId) internal virtual {}
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/**
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* @dev Default additional encoded parameters used by castVote methods that don't include them
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*
@@ -649,6 +656,8 @@ abstract contract Governor is Context, ERC165, EIP712, Nonces, IGovernor, IERC72
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emit VoteCastWithParams(account, proposalId, support, votedWeight, reason, params);
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}
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_tallyUpdated(proposalId);
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return votedWeight;
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}
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@@ -732,7 +741,7 @@ abstract contract Governor is Context, ERC165, EIP712, Nonces, IGovernor, IERC72
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*
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* If requirements are not met, reverts with a {GovernorUnexpectedProposalState} error.
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*/
735-
function _validateStateBitmap(uint256 proposalId, bytes32 allowedStates) private view returns (ProposalState) {
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function _validateStateBitmap(uint256 proposalId, bytes32 allowedStates) internal view returns (ProposalState) {
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ProposalState currentState = state(proposalId);
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if (_encodeStateBitmap(currentState) & allowedStates == bytes32(0)) {
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revert GovernorUnexpectedProposalState(proposalId, currentState, allowedStates);

‎contracts/governance/README.adoc

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@@ -30,6 +30,8 @@ Counting modules determine valid voting options.
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* {GovernorCountingFractional}: A more modular voting system that allows a user to vote with only part of its voting power, and to split that weight arbitrarily between the 3 different options (Against, For and Abstain).
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* {GovernorCountingOverridable}: An extended version of `GovernorCountingSimple` which allows delegatees to override their delegates while the vote is live.
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Timelock extensions add a delay for governance decisions to be executed. The workflow is extended to require a `queue` step before execution. With these modules, proposals are executed by the external timelock contract, thus it is the timelock that has to hold the assets that are being governed.
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* {GovernorTimelockAccess}: Connects with an instance of an {AccessManager}. This allows restrictions (and delays) enforced by the manager to be considered by the Governor and integrated into the AccessManager's "schedule + execute" workflow.
@@ -66,6 +68,8 @@ NOTE: Functions of the `Governor` contract do not include access control. If you
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{{GovernorCountingFractional}}
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{{GovernorCountingOverride}}
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{{GovernorVotes}}
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{{GovernorVotesQuorumFraction}}
@@ -88,6 +92,8 @@ NOTE: Functions of the `Governor` contract do not include access control. If you
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{{Votes}}
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{{VotesExtended}}
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== Timelock
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In a governance system, the {TimelockController} contract is in charge of introducing a delay between a proposal and its execution. It can be used with or without a {Governor}.

‎contracts/governance/extensions/GovernorCountingOverridable.sol

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// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.20;
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import {SignatureChecker} from "../../utils/cryptography/SignatureChecker.sol";
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import {SafeCast} from "../../utils/math/SafeCast.sol";
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import {VotesExtended} from "../utils/VotesExtended.sol";
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import {GovernorVotes} from "./GovernorVotes.sol";
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/**
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* @dev Extension of {Governor} which enables delegatees to override the vote of their delegates. This module requires a
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* token token that inherits `VotesExtended`.
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*/
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abstract contract GovernorCountingOverridable is GovernorVotes {
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bytes32 public constant OVERRIDE_BALLOT_TYPEHASH =
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keccak256("OverrideBallot(uint256 proposalId,uint8 support,address voter,uint256 nonce,string reason)");
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18+
/**
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* @dev Supported vote types. Matches Governor Bravo ordering.
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*/
21+
enum VoteType {
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Against,
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For,
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Abstain
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}
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struct VoteReceipt {
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uint8 casted; // 0 if vote was not casted. Otherwise: support + 1
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bool hasOverriden;
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uint208 overridenWeight;
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}
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struct ProposalVote {
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uint256[3] votes;
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mapping(address voter => VoteReceipt) voteReceipt;
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}
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event VoteReduced(address indexed voter, uint256 proposalId, uint8 support, uint256 weight);
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event OverrideVoteCast(address indexed voter, uint256 proposalId, uint8 support, uint256 weight, string reason);
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error GovernorAlreadyOverridenVote(address account);
42+
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mapping(uint256 proposalId => ProposalVote) private _proposalVotes;
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/**
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* @dev See {IGovernor-COUNTING_MODE}.
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*/
48+
// solhint-disable-next-line func-name-mixedcase
49+
function COUNTING_MODE() public pure virtual override returns (string memory) {
50+
return "support=bravo,override&quorum=for,abstain&overridable=true";
51+
}
52+
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/**
54+
* @dev See {IGovernor-hasVoted}.
55+
*/
56+
function hasVoted(uint256 proposalId, address account) public view virtual override returns (bool) {
57+
return _proposalVotes[proposalId].voteReceipt[account].casted != 0;
58+
}
59+
60+
/**
61+
* @dev Check if an `account` has overridden their delegate for a proposal.
62+
*/
63+
function hasVotedOverride(uint256 proposalId, address account) public view virtual returns (bool) {
64+
return _proposalVotes[proposalId].voteReceipt[account].hasOverriden;
65+
}
66+
67+
/**
68+
* @dev Accessor to the internal vote counts.
69+
*/
70+
function proposalVotes(
71+
uint256 proposalId
72+
) public view virtual returns (uint256 againstVotes, uint256 forVotes, uint256 abstainVotes) {
73+
uint256[3] storage votes = _proposalVotes[proposalId].votes;
74+
return (votes[uint8(VoteType.Against)], votes[uint8(VoteType.For)], votes[uint8(VoteType.Abstain)]);
75+
}
76+
77+
/**
78+
* @dev See {Governor-_quorumReached}.
79+
*/
80+
function _quorumReached(uint256 proposalId) internal view virtual override returns (bool) {
81+
uint256[3] storage votes = _proposalVotes[proposalId].votes;
82+
return quorum(proposalSnapshot(proposalId)) <= votes[uint8(VoteType.For)] + votes[uint8(VoteType.Abstain)];
83+
}
84+
85+
/**
86+
* @dev See {Governor-_voteSucceeded}. In this module, the forVotes must be strictly over the againstVotes.
87+
*/
88+
function _voteSucceeded(uint256 proposalId) internal view virtual override returns (bool) {
89+
uint256[3] storage votes = _proposalVotes[proposalId].votes;
90+
return votes[uint8(VoteType.For)] > votes[uint8(VoteType.Against)];
91+
}
92+
93+
/**
94+
* @dev See {Governor-_countVote}. In this module, the support follows the `VoteType` enum (from Governor Bravo).
95+
*
96+
* NOTE: called by {Governor-_castVote} which emits the {IGovernor-VoteCast} (or {IGovernor-VoteCastWithParams})
97+
* event.
98+
*/
99+
function _countVote(
100+
uint256 proposalId,
101+
address account,
102+
uint8 support,
103+
uint256 totalWeight,
104+
bytes memory /*params*/
105+
) internal virtual override returns (uint256) {
106+
ProposalVote storage proposalVote = _proposalVotes[proposalId];
107+
108+
if (support > uint8(VoteType.Abstain)) {
109+
revert GovernorInvalidVoteType();
110+
}
111+
112+
if (proposalVote.voteReceipt[account].casted != 0) {
113+
revert GovernorAlreadyCastVote(account);
114+
}
115+
116+
totalWeight -= proposalVote.voteReceipt[account].overridenWeight;
117+
proposalVote.votes[support] += totalWeight;
118+
proposalVote.voteReceipt[account].casted = support + 1;
119+
120+
return totalWeight;
121+
}
122+
123+
/// @dev Variant of {Governor-_countVote} that deals with vote overrides.
124+
function _countOverride(uint256 proposalId, address account, uint8 support) internal virtual returns (uint256) {
125+
ProposalVote storage proposalVote = _proposalVotes[proposalId];
126+
127+
if (support > uint8(VoteType.Abstain)) {
128+
revert GovernorInvalidVoteType();
129+
}
130+
131+
if (proposalVote.voteReceipt[account].hasOverriden) {
132+
revert GovernorAlreadyOverridenVote(account);
133+
}
134+
135+
uint256 proposalSnapshot = proposalSnapshot(proposalId);
136+
uint256 overridenWeight = VotesExtended(address(token())).getPastBalanceOf(account, proposalSnapshot);
137+
address delegate = VotesExtended(address(token())).getPastDelegate(account, proposalSnapshot);
138+
uint8 delegateCasted = proposalVote.voteReceipt[delegate].casted;
139+
140+
proposalVote.voteReceipt[account].hasOverriden = true;
141+
proposalVote.votes[support] += overridenWeight;
142+
if (delegateCasted == 0) {
143+
proposalVote.voteReceipt[delegate].overridenWeight += SafeCast.toUint208(overridenWeight);
144+
} else {
145+
uint8 delegateSupport = delegateCasted - 1;
146+
proposalVote.votes[delegateSupport] -= overridenWeight;
147+
emit VoteReduced(delegate, proposalId, delegateSupport, overridenWeight);
148+
}
149+
150+
return overridenWeight;
151+
}
152+
153+
/// @dev variant of {Governor-_castVote} that deals with vote overrides.
154+
function _castOverride(
155+
uint256 proposalId,
156+
address account,
157+
uint8 support,
158+
string calldata reason
159+
) internal virtual returns (uint256) {
160+
_validateStateBitmap(proposalId, _encodeStateBitmap(ProposalState.Active));
161+
162+
uint256 overridenWeight = _countOverride(proposalId, account, support);
163+
164+
emit OverrideVoteCast(account, proposalId, support, overridenWeight, reason);
165+
166+
_tallyUpdated(proposalId);
167+
168+
return overridenWeight;
169+
}
170+
171+
/// @dev Public function for casting an override vote
172+
function castOverrideVote(
173+
uint256 proposalId,
174+
uint8 support,
175+
string calldata reason
176+
) public virtual returns (uint256) {
177+
address voter = _msgSender();
178+
return _castOverride(proposalId, voter, support, reason);
179+
}
180+
181+
/// @dev Public function for casting an override vote using a voter's signature
182+
function castOverrideVoteBySig(
183+
uint256 proposalId,
184+
uint8 support,
185+
address voter,
186+
string calldata reason,
187+
bytes calldata signature
188+
) public virtual returns (uint256) {
189+
bool valid = SignatureChecker.isValidSignatureNow(
190+
voter,
191+
_hashTypedDataV4(
192+
keccak256(
193+
abi.encode(
194+
OVERRIDE_BALLOT_TYPEHASH,
195+
proposalId,
196+
support,
197+
voter,
198+
_useNonce(voter),
199+
keccak256(bytes(reason))
200+
)
201+
)
202+
),
203+
signature
204+
);
205+
206+
if (!valid) {
207+
revert GovernorInvalidSignature(voter);
208+
}
209+
210+
return _castOverride(proposalId, voter, support, reason);
211+
}
212+
}

‎contracts/governance/extensions/GovernorPreventLateQuorum.sol

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@@ -44,20 +44,12 @@ abstract contract GovernorPreventLateQuorum is Governor {
4444
}
4545

4646
/**
47-
* @dev Casts a vote and detects if it caused quorum to be reached, potentially extending the voting period. See
48-
* {Governor-_castVote}.
47+
* @dev Vote tally updated and detects if it caused quorum to be reached, potentially extending the voting period.
4948
*
5049
* May emit a {ProposalExtended} event.
5150
*/
52-
function _castVote(
53-
uint256 proposalId,
54-
address account,
55-
uint8 support,
56-
string memory reason,
57-
bytes memory params
58-
) internal virtual override returns (uint256) {
59-
uint256 result = super._castVote(proposalId, account, support, reason, params);
60-
51+
function _tallyUpdated(uint256 proposalId) internal virtual override {
52+
super._tallyUpdated(proposalId);
6153
if (_extendedDeadlines[proposalId] == 0 && _quorumReached(proposalId)) {
6254
uint48 extendedDeadline = clock() + lateQuorumVoteExtension();
6355

@@ -67,8 +59,6 @@ abstract contract GovernorPreventLateQuorum is Governor {
6759

6860
_extendedDeadlines[proposalId] = extendedDeadline;
6961
}
70-
71-
return result;
7262
}
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7464
/**

‎contracts/governance/utils/VotesExtended.sol

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// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.20;
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import {Checkpoints} from "../../utils/structs/Checkpoints.sol";
5+
import {Votes} from "./Votes.sol";
6+
import {SafeCast} from "../../utils/math/SafeCast.sol";
7+
8+
/**
9+
* @dev Extension of {Votes} that adds exposes checkpoints for delegations and balances.
10+
*/
11+
abstract contract VotesExtended is Votes {
12+
using SafeCast for uint256;
13+
using Checkpoints for Checkpoints.Trace160;
14+
using Checkpoints for Checkpoints.Trace208;
15+
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mapping(address delegatee => Checkpoints.Trace160) private _delegateCheckpoints;
17+
mapping(address account => Checkpoints.Trace208) private _balanceOfCheckpoints;
18+
19+
/**
20+
* @dev Returns the delegate of an `account` at a specific moment in the past. If the `clock()` is
21+
* configured to use block numbers, this will return the value at the end of the corresponding block.
22+
*
23+
* Requirements:
24+
*
25+
* - `timepoint` must be in the past. If operating using block numbers, the block must be already mined.
26+
*/
27+
function getPastDelegate(address account, uint256 timepoint) public view virtual returns (address) {
28+
uint48 currentTimepoint = clock();
29+
if (timepoint >= currentTimepoint) {
30+
revert ERC5805FutureLookup(timepoint, currentTimepoint);
31+
}
32+
return address(_delegateCheckpoints[account].upperLookupRecent(timepoint.toUint48()));
33+
}
34+
35+
/**
36+
* @dev Returns the `balanceOf` of an `account` at a specific moment in the past. If the `clock()` is
37+
* configured to use block numbers, this will return the value at the end of the corresponding block.
38+
*
39+
* Requirements:
40+
*
41+
* - `timepoint` must be in the past. If operating using block numbers, the block must be already mined.
42+
*/
43+
function getPastBalanceOf(address account, uint256 timepoint) public view virtual returns (uint256) {
44+
uint48 currentTimepoint = clock();
45+
if (timepoint >= currentTimepoint) {
46+
revert ERC5805FutureLookup(timepoint, currentTimepoint);
47+
}
48+
return _balanceOfCheckpoints[account].upperLookupRecent(timepoint.toUint48());
49+
}
50+
51+
/// @inheritdoc Votes
52+
function _delegate(address account, address delegatee) internal virtual override {
53+
super._delegate(account, delegatee);
54+
55+
_delegateCheckpoints[account].push(clock(), uint160(delegatee));
56+
}
57+
58+
/// @inheritdoc Votes
59+
function _transferVotingUnits(address from, address to, uint256 amount) internal virtual override {
60+
super._transferVotingUnits(from, to, amount);
61+
if (from != to) {
62+
if (from != address(0)) {
63+
_balanceOfCheckpoints[from].push(clock(), _getVotingUnits(from).toUint208());
64+
}
65+
if (to != address(0)) {
66+
_balanceOfCheckpoints[to].push(clock(), _getVotingUnits(to).toUint208());
67+
}
68+
}
69+
}
70+
}

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