Using distribution function error in Solidity

Question

I have a simple contract where I implemented a mechanism that sends ETH to contributors. When I call contribute function everything works great, but if I use something like that bulkSend(msg.value / 2) I have an error:

revert The transaction has been reverted to the initial state. Note: The called function should be payable if you send value and the value you send should be less than your current balance. Debug the transaction to get more information.

What's wrong?

pragma solidity >=0.4.22 <0.7.0;

contract Test {

    address payable[] public contributors;

    constructor() public {}

    function bulkSend(uint256 amount) public payable {
        uint256 share = amount / contributors.length;
        uint256 length = contributors.length;
        uint256 currentSum = 0;
        for (uint256 i = 0; i < length; i++) {
            require(share > 0);
            currentSum += share;
            require(currentSum <= msg.value);
            contributors[i].transfer(share);
        }
        require(currentSum == msg.value);
    }

    function contribute() public payable {
        contributors.push(msg.sender);
        bulkSend(msg.value);
    }
}

Answer 1

You have a guard in bulkSend: require(currentSum == msg.value).

If you send a transaction where amount != msg.value OR amount % contributors.length != 0 then this requirement will fail, because this requirement will throw.

A good practice is to include "error messages" in your require statements. This helps you debugging these transactions.