DAO accounting for the nouns fungible token

packages/nouns-contracts/contracts/governance/NounsDAOAdmin.sol

@@ -102,6 +102,9 @@ library NounsDAOAdmin {
     /// @notice Emitted when the main timelock, timelockV1 and admin are set
     event TimelocksAndAdminSet(address timelock, address timelockV1, address admin);
 
+    /// @notice Emitted when the Nouns Fungible Token address is set
+    event NounsFungibleTokenSet(address oldNounsFungibleToken, address newNounsFungibleToken);
+
     /// @notice The minimum setable proposal threshold
     uint256 public constant MIN_PROPOSAL_THRESHOLD_BPS = 1; // 1 basis point or 0.01%
 
@@ -457,10 +460,20 @@ library NounsDAOAdmin {
     }
 
     /**
-     * @notice Admin function for setting the ERC20 tokens that are used when splitting funds to a fork
+     * @notice Admin function for setting the ERC20 tokens that are used when splitting funds to a fork.
+     * Reverts if `erc20tokens` includes `nounsFungibleToken` and `nounsFungibleToken` is set.
      */
     function _setErc20TokensToIncludeInFork(address[] calldata erc20tokens) public onlyAdmin {
         checkForDuplicates(erc20tokens);
+        address fungibleToken = ds().nounsFungibleToken;
+        if (fungibleToken != address(0)) {
+            for (uint256 i = 0; i < erc20tokens.length; i++) {
+                require(
+                    erc20tokens[i] != fungibleToken,
+                    'NounsDAO::_setErc20TokensToIncludeInFork: cannot include fungible token'
+                );
+            }
+        }
 
         emit ERC20TokensToIncludeInForkSet(ds().erc20TokensToIncludeInFork, erc20tokens);
 
@@ -537,12 +550,13 @@ library NounsDAOAdmin {
     }
 
     /**
-     * @notice Admin function for zeroing out the state variable `voteSnapshotBlockSwitchProposalId`
-     * @dev We want to zero-out this state slot so we can remove this temporary variable from contract code and 
-     * be ready to reuse this slot.
+     * @notice Admin function for setting the canonical Nouns Fungible Token address
      */
-    function _zeroOutVoteSnapshotBlockSwitchProposalId() external onlyAdmin {
-        ds().voteSnapshotBlockSwitchProposalId = 0;
+    function _setNounsFungibleToken(address newNounsFungibleToken) public onlyAdmin {
+        address oldNounsFungibleToken = ds().nounsFungibleToken;
+        ds().nounsFungibleToken = newNounsFungibleToken;
+
+        emit NounsFungibleTokenSet(oldNounsFungibleToken, newNounsFungibleToken);
     }
 
     function _writeQuorumParamsCheckpoint(NounsDAOTypes.DynamicQuorumParams memory params) internal {

packages/nouns-contracts/contracts/governance/NounsDAOInterfaces.sol

@@ -404,9 +404,8 @@ interface NounsDAOTypes {
         uint256 forkThresholdBPS;
         /// @notice Address of the original timelock
         INounsDAOExecutor timelockV1;
-        /// @dev Make sure this stays the last variable in this struct, so we can delete it in the next version
-        /// @dev To be zeroed-out in the upcoming DAO upgrade.
-        uint256 voteSnapshotBlockSwitchProposalId;
+        /// @notice The address of the Nouns-backed ERC20 token
+        address nounsFungibleToken;
     }
 
     struct Proposal {

packages/nouns-contracts/contracts/governance/NounsDAOLogicV4.sol

@@ -925,8 +925,8 @@ contract NounsDAOLogicV4 is NounsDAOStorage, NounsDAOEventsV3 {
         return address(ds.timelockV1);
     }
 
-    function voteSnapshotBlockSwitchProposalId() public view returns (uint256) {
-        return ds.voteSnapshotBlockSwitchProposalId;
+    function nounsFungibleToken() public view returns (address) {
+        return ds.nounsFungibleToken;
     }
 
     receive() external payable {}

packages/nouns-contracts/contracts/governance/fork/NounsDAOFork.sol

@@ -21,6 +21,10 @@ import { NounsDAOTypes, INounsDAOForkEscrow, INounsDAOExecutorV2 } from '../Noun
 import { IERC20 } from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 import { NounsTokenFork } from './newdao/token/NounsTokenFork.sol';
 
+interface NounsFungibleToken {
+    function redeemableNFTsBalance(address account) external view returns (uint256);
+}
+
 library NounsDAOFork {
     error ForkThresholdNotMet();
     error ForkPeriodNotActive();
@@ -161,10 +165,9 @@ library NounsDAOFork {
      * @dev Only the DAO can call this function
      * @param tokenIds the tokenIds to withdraw
      */
-    function withdrawDAONounsFromEscrowToTreasury(
-        NounsDAOTypes.Storage storage ds,
-        uint256[] calldata tokenIds
-    ) external {
+    function withdrawDAONounsFromEscrowToTreasury(NounsDAOTypes.Storage storage ds, uint256[] calldata tokenIds)
+        external
+    {
         withdrawDAONounsFromEscrow(ds, tokenIds, address(ds.timelock));
     }
 
@@ -216,11 +219,20 @@ library NounsDAOFork {
 
     /**
      * @notice Returns the number of nouns in supply minus nouns owned by the DAO, i.e. held in the treasury or in an
-     * escrow after it has closed.
+     * escrow after it has closed, minus nouns hold via holding the nouns fungible token.
      * This is used when calculating proposal threshold, quorum, fork threshold & treasury split.
      */
     function adjustedTotalSupply(NounsDAOTypes.Storage storage ds) internal view returns (uint256) {
-        return ds.nouns.totalSupply() - ds.nouns.balanceOf(address(ds.timelock)) - ds.forkEscrow.numTokensOwnedByDAO();
+        uint256 nounsHeldViaFungibleToken = 0;
+        address tokenAddress = ds.nounsFungibleToken;
+        if (tokenAddress != address(0)) {
+            nounsHeldViaFungibleToken = NounsFungibleToken(tokenAddress).redeemableNFTsBalance(address(ds.timelock));
+        }
+        return
+            ds.nouns.totalSupply() -
+            ds.nouns.balanceOf(address(ds.timelock)) -
+            ds.forkEscrow.numTokensOwnedByDAO() -
+            nounsHeldViaFungibleToken;
     }
 
     /**

packages/nouns-contracts/contracts/interfaces/INounsDAOLogic.sol

@@ -444,6 +444,11 @@ interface INounsDAOLogic {
      */
     function _setTimelocksAndAdmin(address newTimelock, address newTimelockV1, address newAdmin) external;
 
+    /**
+     * @notice Admin function for setting the canonical Nouns Fungible Token address
+     */
+    function _setNounsFungibleToken(address newNounsFungibleToken) external;
+
     /**
      * @notice Admin function for zeroing out the state variable `voteSnapshotBlockSwitchProposalId`
      * @dev We want to zero-out this state slot so we can remove this temporary variable from contract code and

packages/nouns-contracts/test/foundry/NounsDAOLogic/NounsDAOAdmin.t.sol

@@ -349,18 +349,6 @@ contract NounsDAOLogicAdminTest is NounsDAOLogicBaseTest {
         assertEq(dao.forkThresholdBPS(), 42);
     }
 
-    function test__zeroOutVoteSnapshotBlockSwitchProposalId_onlyAdmin() public {
-        vm.expectRevert(NounsDAOAdmin.AdminOnly.selector);
-        dao._zeroOutVoteSnapshotBlockSwitchProposalId();
-    }
-
-    function test__zeroOutVoteSnapshotBlockSwitchProposalId_works() public {
-        vm.prank(address(dao.timelock()));
-        dao._zeroOutVoteSnapshotBlockSwitchProposalId();
-
-        assertEq(dao.voteSnapshotBlockSwitchProposalId(), 0);
-    }
-
     function test_setErc20TokensToIncludeInFork_onlyAdmin() public {
         tokens = [address(1), address(2)];
 
@@ -400,6 +388,22 @@ contract NounsDAOLogicAdminTest is NounsDAOLogicBaseTest {
         dao._setErc20TokensToIncludeInFork(tokens_);
     }
 
+    function test__setErc20TokensToIncludeInFork_givenFungibleTokenInInput_reverts() public {
+        address fungibleToken = makeAddr('fungible token');
+        vm.prank(address(dao.timelock()));
+        dao._setNounsFungibleToken(fungibleToken);
+
+        address anotherToken = makeAddr('another token');
+
+        address[] memory tokens_ = new address[](2);
+        tokens_[0] = anotherToken;
+        tokens_[1] = fungibleToken;
+
+        vm.prank(address(dao.timelock()));
+        vm.expectRevert('NounsDAO::_setErc20TokensToIncludeInFork: cannot include fungible token');
+        dao._setErc20TokensToIncludeInFork(tokens_);
+    }
+
     function test_setForkEscrow_onlyAdmin() public {
         vm.expectRevert(NounsDAOAdmin.AdminOnly.selector);
         dao._setForkEscrow(address(1));

packages/nouns-contracts/test/foundry/NounsDAOLogic/NounsDAOFork.t.sol

@@ -10,6 +10,18 @@ import { NounsDAOForkEscrow } from '../../../contracts/governance/fork/NounsDAOF
 import { IERC721 } from '@openzeppelin/contracts/token/ERC721/IERC721.sol';
 import { INounsDAOForkEscrow } from '../../../contracts/governance/NounsDAOInterfaces.sol';
 
+contract FungibleTokenMock {
+    mapping(address => uint256) values;
+
+    function set(address account, uint256 value) public {
+        values[account] = value;
+    }
+
+    function redeemableNFTsBalance(address account) external view returns (uint256) {
+        return values[account];
+    }
+}
+
 abstract contract DAOForkZeroState is NounsDAOLogicBaseTest {
     address tokenHolder = makeAddr('tokenHolder');
     address tokenHolder2 = makeAddr('tokenHolder2');
@@ -45,7 +57,11 @@ abstract contract DAOForkZeroState is NounsDAOLogicBaseTest {
         escrow = dao.forkEscrow();
     }
 
-    function assertOwnerOfTokens(address token, uint256[] memory tokenIds_, address owner) internal {
+    function assertOwnerOfTokens(
+        address token,
+        uint256[] memory tokenIds_,
+        address owner
+    ) internal {
         for (uint256 i = 0; i < tokenIds_.length; i++) {
             assertEq(IERC721(token).ownerOf(tokenIds_[i]), owner);
         }
@@ -307,6 +323,25 @@ contract DAOForkSignaledOverThresholdStateTest is DAOForkSignaledOverThresholdSt
         vm.roll(block.number + 1);
         propose(someone, address(0), 0, '', '', '');
     }
+
+    function test_adjustedTotalSupply_takesFungibleTokensIntoAccount() public {
+        dao.executeFork();
+
+        // Before token is set
+        assertEq(dao.adjustedTotalSupply(), 15);
+
+        FungibleTokenMock ft = new FungibleTokenMock();
+        vm.prank(address(dao.timelock()));
+        dao._setNounsFungibleToken(address(ft));
+
+        // After token is set, before any balance is set
+        assertEq(dao.adjustedTotalSupply(), 15);
+
+        ft.set(address(dao.timelock()), 2);
+
+        // After fungible token balance is set
+        assertEq(dao.adjustedTotalSupply(), 13);
+    }
 }
 
 abstract contract DAOForkExecutedState is DAOForkSignaledOverThresholdState {
@@ -339,6 +374,27 @@ contract DAOForkExecutedStateTest is DAOForkExecutedState {
         dao.withdrawFromForkEscrow(tokenIds);
     }
 
+    function test_adjustedTotalSupply_takesFungibleTokensIntoAccount() public {
+        // Before join fork
+        assertEq(dao.adjustedTotalSupply(), 15);
+
+        tokenIds = [8, 9];
+        proposalIds = [1, 2];
+        vm.prank(tokenHolder);
+        dao.joinFork(tokenIds, proposalIds, 'some reason');
+
+        // After join fork, before fungible token balance is set
+        assertEq(dao.adjustedTotalSupply(), 13);
+
+        FungibleTokenMock ft = new FungibleTokenMock();
+        vm.prank(address(dao.timelock()));
+        dao._setNounsFungibleToken(address(ft));
+        ft.set(address(dao.timelock()), 3);
+
+        // After fungible token balance is set
+        assertEq(dao.adjustedTotalSupply(), 10);
+    }
+
     function test_joinFork() public {
         tokenIds = [8, 9];
         proposalIds = [1, 2];

packages/nouns-contracts/test/foundry/Upgrade/UpgradeMainnetFork.t.sol

@@ -44,6 +44,11 @@ abstract contract UpgradeMainnetForkBaseTest is Test {
         vm.deal(address(NOUNS_DAO_PROXY_MAINNET), 100 ether);
         vm.fee(50 gwei);
         vm.txGasPrice(50 gwei);
+
+        // zero-out the slot where `voteSnapshotBlockSwitchProposalId` was
+        // as will happen in the upcoming upgrade
+        // so that `nounsFungibleToken` will be address(0) by default
+        vm.store(address(NOUNS_DAO_PROXY_MAINNET), bytes32(uint256(0x19)), bytes32(uint256(0)));
     }
 
     function propose(
@@ -177,20 +182,6 @@ contract DAOUpgradeMainnetForkTest is UpgradeMainnetForkBaseTest {
         assertEq(expectedVotingDelay, NOUNS_DAO_PROXY_MAINNET.votingDelay());
     }
 
-    function test_voteSnapshotBlockSwitchProposalId_zeroOutWorks() public {
-        assertNotEq(NOUNS_DAO_PROXY_MAINNET.voteSnapshotBlockSwitchProposalId(), 0);
-
-        uint256 proposalId = propose(
-            address(NOUNS_DAO_PROXY_MAINNET),
-            0,
-            '_zeroOutVoteSnapshotBlockSwitchProposalId()',
-            ''
-        );
-        voteAndExecuteProposal(proposalId);
-
-        assertEq(NOUNS_DAO_PROXY_MAINNET.voteSnapshotBlockSwitchProposalId(), 0);
-    }
-
     function test_clientId_savedOnProposals() public {
         uint32 expectedClientId = 42;
         uint256 proposalId = propose(address(NOUNS_DAO_PROXY_MAINNET), 0, '', '', expectedClientId);