Execute a law

The executeLaw function is the main entry point for executing a law in the Powers protocol. It handles the complete execution flow of a law, from validation to state changes.

Execution Flow

1. Initial Validation

function executeLaw(
    address caller,
    uint16 lawId,
    bytes calldata lawCalldata,
    uint256 nonce
) public returns (bool success)

The function first validates:

• The caller is the Powers contract

• The law is properly initialized

• The law hash is valid

2. Validation Checks

Two sets of checks are performed:

Proposal Checks

checksAtPropose(caller, laws[lawHash].conditions, lawCalldata, nonce, msg.sender);

• Validates parent law completion

• Checks role permissions

• Verifies input parameters

Execution Checks

checksAtExecute(
    caller,
    laws[lawHash].conditions,
    lawCalldata,
    nonce,
    laws[lawHash].executions.executions,
    msg.sender,
    lawId
);

• Validates execution timing

• Checks proposal success

• Verifies execution delay

3. Law Execution

The law's logic is executed through handleRequest:

(
    uint256 actionId,
    address[] memory targets,
    uint256[] memory values,
    bytes[] memory calldatas,
    bytes memory stateChange
) = handleRequest(caller, msg.sender, lawId, lawCalldata, nonce);

4. State Changes

If state changes are required:

if (stateChange.length > 0) {
    _changeState(lawHash, stateChange);
}

5. Reply to Powers

If execution targets are provided:

if (targets.length > 0) {
    _replyPowers(lawId, actionId, targets, values, calldatas);
}

6. Execution Tracking

The execution is recorded:

laws[lawHash].executions.executions.push(uint48(block.number));
laws[lawHash].executions.actionsIds.push(actionId);

Error Handling

The following errors may be thrown during execution:

• Law__OnlyPowers: Caller is not the Powers contract

• Law__ProposalNotSucceeded: Proposal has not succeeded

• Law__ExecutionGapTooSmall: Execution gap is too small

• Law__DeadlineNotPassed: Execution deadline has not passed

Best Practices

1. Execution Safety

   • Validate all inputs

   • Check execution conditions

   • Verify state consistency

   • Handle errors gracefully

2. Gas Optimization

   • Minimize state changes

   • Use efficient data structures

   • Cache frequently accessed values

   • Batch operations when possible

3. State Management

   • Update state atomically

   • Validate state transitions

   • Emit appropriate events

   • Maintain state consistency

4. Security

   • Validate caller permissions

   • Check for reentrancy

   • Verify execution conditions

   • Protect against manipulation

Example Implementation

function executeLaw(
    address caller,
    uint16 lawId,
    bytes calldata lawCalldata,
    uint256 nonce
) public returns (bool success) {
    bytes32 lawHash = LawUtilities.hashLaw(msg.sender, lawId);
    
    // Validate caller
    if (laws[lawHash].executions.powers != msg.sender) {
        revert Law__OnlyPowers();
    }
    
    // Run validation checks
    checksAtPropose(caller, laws[lawHash].conditions, lawCalldata, nonce, msg.sender);
    checksAtExecute(
        caller,
        laws[lawHash].conditions,
        lawCalldata,
        nonce,
        laws[lawHash].executions.executions,
        msg.sender,
        lawId
    );
    
    // Execute law logic
    (
        uint256 actionId,
        address[] memory targets,
        uint256[] memory values,
        bytes[] memory calldatas,
        bytes memory stateChange
    ) = handleRequest(caller, msg.sender, lawId, lawCalldata, nonce);
    
    // Apply state changes
    if (stateChange.length > 0) {
        _changeState(lawHash, stateChange);
    }
    
    // Reply to Powers
    if (targets.length > 0) {
        _replyPowers(lawId, actionId, targets, values, calldatas);
    }
    
    // Record execution
    laws[lawHash].executions.executions.push(uint48(block.number));
    laws[lawHash].executions.actionsIds.push(actionId);
    
    return true;
}