Gas Optimizations

[code423n4]

Using bools for storage incurs overhead

// Booleans are more expensive than uint256 or any type that takes up a full
// word because each write operation emits an extra SLOAD to first read the
// slot's contents, replace the bits taken up by the boolean, and then write
// back. This is the compiler's defense against contract upgrades and
// pointer aliasing, and it cannot be disabled.

you can re order storage variables to save 20_000 gas

   address public override contractor;
    /// @inheritdoc IProject
    bool public override contractorConfirmed;
    /// @inheritdoc IProject
    uint256 public override hashChangeNonce;
    /// @inheritdoc IProject
    uint256 public override totalLent;
    /// @inheritdoc IProject
    uint256 public override totalAllocated;
    /// @inheritdoc IProject
    uint256 public override taskCount;
    /// @inheritdoc IProject
    bool public override contractorDelegated;
    /// @inheritdoc IProject
    uint256 public override lastAllocatedTask;
    /// @inheritdoc IProject
    uint256 public override lastAllocatedChangeOrderTask;

you can take the bool under the other bool because a bool only takes up 1 byte other wise it would take up one slot.
https://github.com/code-423n4/2022-08-rigor/blob/f2498c86dbd0e265f82ec76d9ec576442e896a87/contracts/Project.sol#L70

make i++ into ++i to remove a memory copy

HomeFiProxy.sol:87:        for (uint256 i = 0; i < _length; i++) {
HomeFiProxy.sol:136:        for (uint256 i = 0; i < _length; i++) {
libraries/Tasks.sol:181:        for (uint256 i = 0; i < _length; i++) _alerts[i] = _self.alerts[i];
Project.sol:249:        for (uint256 i = 0; i < _length; i++) {
Project.sol:312:        for (uint256 i = 0; i < _length; i++) {
Project.sol:323:        for (uint256 i = 0; i < _length; i++) {
Project.sol:604:            for (; i < _changeOrderedTask.length; i++) {
Community.sol:625:        for (uint256 i = 0; i < _communities[_communityID].memberCount; i++) {

you can make arrary.length into memory variable to save gas

Project.sol:604:            for (; i < _changeOrderedTask.length; i++) {
Community.sol:625:        for (uint256 i = 0; i < _communities[_communityID].memberCount; i++) {

Use Custom Errors instead of Revert Strings to save Gas

Custom errors from Solidity 0.8.4 are cheaper than revert strings (cheaper deployment cost and runtime cost when the revert condition is met) Source Custom Errors in Solidity: Starting from Solidity v0.8.4, there is a convenient and gas-efficient way to explain to users why an operation failed through the use of custom errors. Until now, you could already use strings to give more information about failures (e.g., revert("Insufficient funds.");), but they are rather expensive, especially when it comes to deploy cost, and it is difficult to use dynamic information in them. Custom errors are defined using the error statement, which can be used inside and outside of contracts (including interfaces and libraries).

HomeFiProxy.sol:41:        require(_address != address(0), "Proxy::0 address");
HomeFiProxy.sol:81:        require(_length == _implementations.length, "Proxy::Lengths !match");
HomeFiProxy.sol:105:        require(
HomeFiProxy.sol:133:        require(_length == _contractAddresses.length, "Proxy::Lengths !match");
libraries/Tasks.sol:44:        require(_self.state == TaskStatus.Inactive, "Task::active");
libraries/Tasks.sol:50:        require(_self.state == TaskStatus.Active, "Task::!Active");
libraries/Tasks.sol:56:        require(
libraries/Tasks.sol:124:        require(_self.subcontractor == _sc, "Task::!SC");
ProjectFactory.sol:36:        require(_address != address(0), "PF::0 address");
ProjectFactory.sol:64:        require(
ProjectFactory.sol:84:        require(_msgSender() == homeFi, "PF::!HomeFiContract");
Disputes.sol:39:        require(_address != address(0), "Disputes::0 address");
Disputes.sol:46:        require(homeFi.admin() == _msgSender(), "Disputes::!Admin");
Disputes.sol:52:        require(homeFi.isProjectExist(_msgSender()), "Disputes::!Project");
Disputes.sol:61:        require(
Disputes.sol:106:        require(
Disputes.sol:183:        require(_result, "Disputes::!Member");
HomeFi.sol:73:        require(admin == _msgSender(), "HomeFi::!Admin");
HomeFi.sol:78:        require(_address != address(0), "HomeFi::0 address");
HomeFi.sol:84:        require(_oldAddress != _newAddress, "HomeFi::!Change");
HomeFi.sol:142:        require(!addrSet, "HomeFi::Set");
HomeFi.sol:192:        require(lenderFee != _newLenderFee, "HomeFi::!Change");
HomeFi.sol:256:        require(
DebtToken.sol:31:        require(
DebtToken.sol:50:        require(_communityContract != address(0), "DebtToken::0 address");
Project.sol:123:        require(!contractorConfirmed, "Project::GC accepted");
Project.sol:132:        require(_projectAddress == address(this), "Project::!projectAddress");
Project.sol:135:        require(_contractor != address(0), "Project::0 address");
Project.sol:150:        require(_msgSender() == builder, "Project::!B");
Project.sol:153:        require(contractor != address(0), "Project::0 address");
Project.sol:166:        // Check for required signatures
Project.sol:176:        require(_nonce == hashChangeNonce, "Project::!Nonce");
Project.sol:189:        require(
Project.sol:195:        require(_cost > 0, "Project::!value>0");
Project.sol:199:        require(
Project.sol:202:            "Project::value>required"
Project.sol:226:            // Check for required signatures
Project.sol:239:        require(_taskCount == taskCount, "Project::!taskCount");
Project.sol:242:        require(_projectAddress == address(this), "Project::!projectAddress");
Project.sol:246:        require(_length == _taskCosts.length, "Project::Lengths !match");
Project.sol:278:        require(_nonce == hashChangeNonce, "Project::!Nonce");
Project.sol:302:        require(
Project.sol:309:        require(_length == _scList.length, "Project::Lengths !match");
Project.sol:342:        require(_projectAddress == address(this), "Project::!Project");
Project.sol:370:                require(tasks[_taskID].getState() == 3, "Project::!Complete");
Project.sol:402:            // Check for required signatures.
Project.sol:407:        require(_project == address(this), "Project::!projectAddress");
Project.sol:435:                    // As this additional amount may not be required by the project.
Project.sol:512:        require(_project == address(this), "Project::!projectAddress");
Project.sol:516:            require(
Project.sol:522:            require(
Project.sol:531:                require(getAlerts(_task)[2], "Project::!SCConfirmed");
Project.sol:755:        require(_sc != address(0), "Project::0 address");
Project.sol:888:        require(
Project.sol:908:        require(
Community.sol:69:        require(_address != address(0), "Community::0 address");
Community.sol:75:        require(_msgSender() == homeFi.admin(), "Community::!admin");
Community.sol:81:        require(
Community.sol:90:        require(
Community.sol:131:        require(
Community.sol:159:        require(
Community.sol:191:        require(
Community.sol:235:        require(
Community.sol:241:        require(homeFi.isProjectExist(_project), "Community::Project !Exists");
Community.sol:248:        require(_community.isMember[_builder], "Community::!Member");
Community.sol:251:        require(
Community.sol:312:        require(
Community.sol:347:        require(
Community.sol:353:        require(
Community.sol:384:        require(
Community.sol:400:        require(
Community.sol:492:        require(
Community.sol:537:        require(_builder == _projectInstance.builder(), "Community::!Builder");
Community.sol:540:        require(
Community.sol:558:        require(!restrictedToAdmin, "Community::restricted");
Community.sol:569:        require(restrictedToAdmin, "Community::!restricted");
Community.sol:748:        // then this fee will be required to be paid again.
Community.sol:769:        require(_repayAmount > 0, "Community::!repay");
Community.sol:797:            require(_lentAndInterest >= _repayAmount, "Community::!Liquid");
Community.sol:893:        require(
mock/HomeFiMock.sol:42:        require(admin == _msgSender(), "HomeFi::!Admin");
mock/HomeFiMock.sol:47:        require(_address != address(0), "HomeFi::0 address");
mock/HomeFiMock.sol:96:        require(!addrSet, "HomeFi::Set");
mock/HomeFiMock.sol:113:        require(admin != _newAdmin, "HomeFi::!Change");
mock/HomeFiMock.sol:124:        require(treasury != _newTreasury, "HomeFi::!Change");
mock/HomeFiMock.sol:134:        require(lenderFee != _newLenderFee, "HomeFi::!Change");
mock/HomeFiMock.sol:175:        require(
mock/HomeFiV2Mock.sol:19:        require(!addrSet2, "Already set once");
interfaces/IProject.sol:38:     * @notice initialize this contract with required parameters. This is initialized by HomeFi contract.
interfaces/IProject.sol:67:     * @param _signature bytes representing signature on _data by required members.
interfaces/IProject.sol:89:     * @param _signature bytes representing signature on _data by required members.
interfaces/IProject.sol:133:     * @param _signature bytes representing signature on _data by required members.
interfaces/IProject.sol:168:     * @param _signature bytes representing signature on _data by required members.
interfaces/IProject.sol:196:     * @param _signature bytes representing signature on _data by required members.
interfaces/ICommunity.sol:23:        uint256 lendingNeeded; // total lending requirement from the community
interfaces/ICommunity.sol:27:        uint256 publishFee; // fee required to be paid to request funds from community
interfaces/ICommunity.sol:162:     * - _publishFee uint256 - project publish fee. This fee is required to be paid before `toggleLendingNeeded` can be called.
interfaces/ICommunity.sol:186:     * This fee is required to be paid before `toggleLendingNeeded` can be called. Hence before asking for any lending.
interfaces/IHomeFi.sol:28:     * @notice initialize this contract with required parameters.
simon@pop-os:~/solidity/code4/2022-08-rigor/contracts$ grep -Rn "" | grep require
HomeFiProxy.sol:41:        require(_address != address(0), "Proxy::0 address");
HomeFiProxy.sol:81:        require(_length == _implementations.length, "Proxy::Lengths !match");
HomeFiProxy.sol:105:        require(
HomeFiProxy.sol:133:        require(_length == _contractAddresses.length, "Proxy::Lengths !match");
libraries/Tasks.sol:44:        require(_self.state == TaskStatus.Inactive, "Task::active");
libraries/Tasks.sol:50:        require(_self.state == TaskStatus.Active, "Task::!Active");
libraries/Tasks.sol:56:        require(
libraries/Tasks.sol:124:        require(_self.subcontractor == _sc, "Task::!SC");
ProjectFactory.sol:36:        require(_address != address(0), "PF::0 address");
ProjectFactory.sol:64:        require(
ProjectFactory.sol:84:        require(_msgSender() == homeFi, "PF::!HomeFiContract");
Disputes.sol:39:        require(_address != address(0), "Disputes::0 address");
Disputes.sol:46:        require(homeFi.admin() == _msgSender(), "Disputes::!Admin");
Disputes.sol:52:        require(homeFi.isProjectExist(_msgSender()), "Disputes::!Project");
Disputes.sol:61:        require(
Disputes.sol:106:        require(
Disputes.sol:183:        require(_result, "Disputes::!Member");
HomeFi.sol:73:        require(admin == _msgSender(), "HomeFi::!Admin");
HomeFi.sol:78:        require(_address != address(0), "HomeFi::0 address");
HomeFi.sol:84:        require(_oldAddress != _newAddress, "HomeFi::!Change");
HomeFi.sol:142:        require(!addrSet, "HomeFi::Set");
HomeFi.sol:192:        require(lenderFee != _newLenderFee, "HomeFi::!Change");
HomeFi.sol:256:        require(
DebtToken.sol:31:        require(
DebtToken.sol:50:        require(_communityContract != address(0), "DebtToken::0 address");
Project.sol:123:        require(!contractorConfirmed, "Project::GC accepted");
Project.sol:132:        require(_projectAddress == address(this), "Project::!projectAddress");
Project.sol:135:        require(_contractor != address(0), "Project::0 address");
Project.sol:150:        require(_msgSender() == builder, "Project::!B");
Project.sol:153:        require(contractor != address(0), "Project::0 address");
Project.sol:166:        // Check for required signatures
Project.sol:176:        require(_nonce == hashChangeNonce, "Project::!Nonce");
Project.sol:189:        require(
Project.sol:195:        require(_cost > 0, "Project::!value>0");
Project.sol:199:        require(
Project.sol:202:            "Project::value>required"
Project.sol:226:            // Check for required signatures
Project.sol:239:        require(_taskCount == taskCount, "Project::!taskCount");
Project.sol:242:        require(_projectAddress == address(this), "Project::!projectAddress");
Project.sol:246:        require(_length == _taskCosts.length, "Project::Lengths !match");
Project.sol:278:        require(_nonce == hashChangeNonce, "Project::!Nonce");
Project.sol:302:        require(
Project.sol:309:        require(_length == _scList.length, "Project::Lengths !match");
Project.sol:342:        require(_projectAddress == address(this), "Project::!Project");
Project.sol:370:                require(tasks[_taskID].getState() == 3, "Project::!Complete");
Project.sol:402:            // Check for required signatures.
Project.sol:407:        require(_project == address(this), "Project::!projectAddress");
Project.sol:435:                    // As this additional amount may not be required by the project.
Project.sol:512:        require(_project == address(this), "Project::!projectAddress");
Project.sol:516:            require(
Project.sol:522:            require(
Project.sol:531:                require(getAlerts(_task)[2], "Project::!SCConfirmed");
Project.sol:755:        require(_sc != address(0), "Project::0 address");
Project.sol:888:        require(
Project.sol:908:        require(
Community.sol:69:        require(_address != address(0), "Community::0 address");
Community.sol:75:        require(_msgSender() == homeFi.admin(), "Community::!admin");
Community.sol:81:        require(
Community.sol:90:        require(
Community.sol:131:        require(
Community.sol:159:        require(
Community.sol:191:        require(
Community.sol:235:        require(
Community.sol:241:        require(homeFi.isProjectExist(_project), "Community::Project !Exists");
Community.sol:248:        require(_community.isMember[_builder], "Community::!Member");
Community.sol:251:        require(
Community.sol:312:        require(
Community.sol:347:        require(
Community.sol:353:        require(
Community.sol:384:        require(
Community.sol:400:        require(
Community.sol:492:        require(
Community.sol:537:        require(_builder == _projectInstance.builder(), "Community::!Builder");
Community.sol:540:        require(
Community.sol:558:        require(!restrictedToAdmin, "Community::restricted");
Community.sol:569:        require(restrictedToAdmin, "Community::!restricted");
Community.sol:748:        // then this fee will be required to be paid again.
Community.sol:769:        require(_repayAmount > 0, "Community::!repay");
Community.sol:797:            require(_lentAndInterest >= _repayAmount, "Community::!Liquid");
Community.sol:893:        require(
mock/HomeFiMock.sol:42:        require(admin == _msgSender(), "HomeFi::!Admin");
mock/HomeFiMock.sol:47:        require(_address != address(0), "HomeFi::0 address");
mock/HomeFiMock.sol:96:        require(!addrSet, "HomeFi::Set");
mock/HomeFiMock.sol:113:        require(admin != _newAdmin, "HomeFi::!Change");
mock/HomeFiMock.sol:124:        require(treasury != _newTreasury, "HomeFi::!Change");
mock/HomeFiMock.sol:134:        require(lenderFee != _newLenderFee, "HomeFi::!Change");
mock/HomeFiMock.sol:175:        require(
mock/HomeFiV2Mock.sol:19:        require(!addrSet2, "Already set once");

make require statements with uint >0 make it != to save gas

Project.sol:195:        require(_cost > 0, "Project::!value>0");
Community.sol:769:        require(_repayAmount > 0, "Community::!repay");

Unchecking arithmetics operations that can’t underflow/overflow

Solidity version 0.8+ comes with implicit overflow and underflow checks on unsigned integers. When an overflow or an underflow isn’t possible (as an example, when a comparison is made before the arithmetic operation), some gas can be saved by using an unchecked block: Checked or Unchecked Arithmetic. I suggest wrapping with an unchecked block:
Same thing with second unchecked because total can't overflow amount cant overflow

• make i into unchecked to save gas only if i is cant get overflowed

HomeFiProxy.sol:87:        for (uint256 i = 0; i < _length; i++) {
HomeFiProxy.sol:136:        for (uint256 i = 0; i < _length; i++) {
libraries/Tasks.sol:181:        for (uint256 i = 0; i < _length; i++) _alerts[i] = _self.alerts[i];
Project.sol:249:        for (uint256 i = 0; i < _length; i++) {
Project.sol:312:        for (uint256 i = 0; i < _length; i++) {
Project.sol:323:        for (uint256 i = 0; i < _length; i++) {
Project.sol:604:            for (; i < _changeOrderedTask.length; i++) {
Community.sol:625:        for (uint256 i = 0; i < _communities[_communityID].memberCount; i++) {

make address(0) and make it into long form to save gas

HomeFiProxy.sol:41:        require(_address != address(0), "Proxy::0 address");
HomeFiProxy.sol:106:            contractAddress[_contractName] == address(0),
libraries/SignatureDecoder.sol:26:            return (address(0));
libraries/SignatureDecoder.sol:36:            return (address(0));
ProjectFactory.sol:35:        // Ensure an address is not the zero address (0x00)
ProjectFactory.sol:36:        require(_address != address(0), "PF::0 address");
Disputes.sol:38:        // Revert if _address zero address (0x00)
Disputes.sol:39:        require(_address != address(0), "Disputes::0 address");
HomeFi.sol:78:        require(_address != address(0), "HomeFi::0 address");
DebtToken.sol:50:        require(_communityContract != address(0), "DebtToken::0 address");
Project.sol:135:        require(_contractor != address(0), "Project::0 address");
Project.sol:153:        require(contractor != address(0), "Project::0 address");
Project.sol:479:            if (_newSC != address(0)) {
Project.sol:486:                tasks[_taskID].subcontractor = address(0);
Project.sol:754:        // Revert if sc to invite is address 0
Project.sol:755:        require(_sc != address(0), "Project::0 address");
Project.sol:800:        if (contractor == address(0)) {
Project.sol:844:        if (contractor == address(0)) {

make admin only function payable to save gas

because payable dosnt check msg.value == 0
HomeFi.sol:157,17185,201