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Extend PaymentSplitter to support ERC20 tokens (#2858)
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* Add MultiPaymentSplitter

with ERC20 support on top of the existing PaymentSplitter

* consistency and linting

* Add MultiPaymentSplitter tests

* fix lint

* add changelog entry

* add MultiPaymentSplitter to documentation

* rework PaymentSplitter to include ERC20 support by default

* remove test file for MultiPaymentSplitter

* fix lint

* completelly split erc20 and token tracking

* address some PR comments

* add notice about rebasing tokens

* fix minor error in tests

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>
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@Amxx @frangio
Amxx and frangio authored Oct 7, 2021
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -8,6 +8,7 @@
* `EIP712`: cache `address(this)` to immutable storage to avoid potential issues if a vanilla contract is used in a delegatecall context. ([#2852](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/#2852))
* Add internal `_setApprovalForAll` to `ERC721` and `ERC1155`. ([#2834](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/2834))
* `Governor`: shift vote start and end by one block to better match Compound's GovernorBravo and prevent voting at the Governor level if the voting snapshot is not ready. ([#2892](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/#2892))
* `PaymentSplitter`: now supports ERC20 assets in addition to Ether. ([#2858](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/#2858))

## 4.3.2 (2021-09-14)

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65 changes: 61 additions & 4 deletions contracts/finance/PaymentSplitter.sol
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Expand Up @@ -2,6 +2,7 @@

pragma solidity ^0.8.0;

import "../token/ERC20/utils/SafeERC20.sol";
import "../utils/Address.sol";
import "../utils/Context.sol";

Expand All @@ -17,10 +18,15 @@ import "../utils/Context.sol";
* `PaymentSplitter` follows a _pull payment_ model. This means that payments are not automatically forwarded to the
* accounts but kept in this contract, and the actual transfer is triggered as a separate step by calling the {release}
* function.
*
* NOTE: This contract assumes that ERC20 tokens will behave similarly to native tokens (Ether). Rebasing tokens, and
* tokens that apply fees during transfers, are likely to not be supported as expected. If in doubt, we encourage you
* to run tests before sending real value to this contract.
*/
contract PaymentSplitter is Context {
event PayeeAdded(address account, uint256 shares);
event PaymentReleased(address to, uint256 amount);
event ERC20PaymentReleased(IERC20 indexed token, address to, uint256 amount);
event PaymentReceived(address from, uint256 amount);

uint256 private _totalShares;
Expand All @@ -30,6 +36,9 @@ contract PaymentSplitter is Context {
mapping(address => uint256) private _released;
address[] private _payees;

mapping(IERC20 => uint256) private _erc20TotalReleased;
mapping(IERC20 => mapping(address => uint256)) private _erc20Released;

/**
* @dev Creates an instance of `PaymentSplitter` where each account in `payees` is assigned the number of shares at
* the matching position in the `shares` array.
Expand Down Expand Up @@ -73,6 +82,14 @@ contract PaymentSplitter is Context {
return _totalReleased;
}

/**
* @dev Getter for the total amount of `token` already released. `token` should be the address of an IERC20
* contract.
*/
function totalReleased(IERC20 token) public view returns (uint256) {
return _erc20TotalReleased[token];
}

/**
* @dev Getter for the amount of shares held by an account.
*/
Expand All @@ -87,6 +104,14 @@ contract PaymentSplitter is Context {
return _released[account];
}

/**
* @dev Getter for the amount of `token` tokens already released to a payee. `token` should be the address of an
* IERC20 contract.
*/
function released(IERC20 token, address account) public view returns (uint256) {
return _erc20Released[token][account];
}

/**
* @dev Getter for the address of the payee number `index`.
*/
Expand All @@ -101,18 +126,50 @@ contract PaymentSplitter is Context {
function release(address payable account) public virtual {
require(_shares[account] > 0, "PaymentSplitter: account has no shares");

uint256 totalReceived = address(this).balance + _totalReleased;
uint256 payment = (totalReceived * _shares[account]) / _totalShares - _released[account];
uint256 totalReceived = address(this).balance + totalReleased();
uint256 payment = _pendingPayment(account, totalReceived, released(account));

require(payment != 0, "PaymentSplitter: account is not due payment");

_released[account] = _released[account] + payment;
_totalReleased = _totalReleased + payment;
_released[account] += payment;
_totalReleased += payment;

Address.sendValue(account, payment);
emit PaymentReleased(account, payment);
}

/**
* @dev Triggers a transfer to `account` of the amount of `token` tokens they are owed, according to their
* percentage of the total shares and their previous withdrawals. `token` must be the address of an IERC20
* contract.
*/
function release(IERC20 token, address account) public virtual {
require(_shares[account] > 0, "PaymentSplitter: account has no shares");

uint256 totalReceived = token.balanceOf(address(this)) + totalReleased(token);
uint256 payment = _pendingPayment(account, totalReceived, released(token, account));

require(payment != 0, "PaymentSplitter: account is not due payment");

_erc20Released[token][account] += payment;
_erc20TotalReleased[token] += payment;

SafeERC20.safeTransfer(token, account, payment);
emit ERC20PaymentReleased(token, account, payment);
}

/**
* @dev internal logic for computing the pending payment of an `account` given the token historical balances and
* already released amounts.
*/
function _pendingPayment(
address account,
uint256 totalReceived,
uint256 alreadyReleased
) private view returns (uint256) {
return (totalReceived * _shares[account]) / _totalShares - alreadyReleased;
}

/**
* @dev Add a new payee to the contract.
* @param account The address of the payee to add.
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140 changes: 103 additions & 37 deletions test/finance/PaymentSplitter.test.js
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Expand Up @@ -4,6 +4,7 @@ const { ZERO_ADDRESS } = constants;
const { expect } = require('chai');

const PaymentSplitter = artifacts.require('PaymentSplitter');
const Token = artifacts.require('ERC20Mock');

contract('PaymentSplitter', function (accounts) {
const [ owner, payee1, payee2, payee3, nonpayee1, payer1 ] = accounts;
Expand Down Expand Up @@ -50,6 +51,7 @@ contract('PaymentSplitter', function (accounts) {
this.shares = [20, 10, 70];

this.contract = await PaymentSplitter.new(this.payees, this.shares);
this.token = await Token.new('MyToken', 'MT', owner, ether('1000'));
});

it('has total shares', async function () {
Expand All @@ -63,10 +65,18 @@ contract('PaymentSplitter', function (accounts) {
}));
});

it('accepts payments', async function () {
await send.ether(owner, this.contract.address, amount);
describe('accepts payments', async function () {
it('Ether', async function () {
await send.ether(owner, this.contract.address, amount);

expect(await balance.current(this.contract.address)).to.be.bignumber.equal(amount);
expect(await balance.current(this.contract.address)).to.be.bignumber.equal(amount);
});

it('Token', async function () {
await this.token.transfer(this.contract.address, amount, { from: owner });

expect(await this.token.balanceOf(this.contract.address)).to.be.bignumber.equal(amount);
});
});

describe('shares', async function () {
Expand All @@ -80,51 +90,107 @@ contract('PaymentSplitter', function (accounts) {
});

describe('release', async function () {
it('reverts if no funds to claim', async function () {
await expectRevert(this.contract.release(payee1),
'PaymentSplitter: account is not due payment',
);
describe('Ether', async function () {
it('reverts if no funds to claim', async function () {
await expectRevert(this.contract.release(payee1),
'PaymentSplitter: account is not due payment',
);
});
it('reverts if non-payee want to claim', async function () {
await send.ether(payer1, this.contract.address, amount);
await expectRevert(this.contract.release(nonpayee1),
'PaymentSplitter: account has no shares',
);
});
});
it('reverts if non-payee want to claim', async function () {
await send.ether(payer1, this.contract.address, amount);
await expectRevert(this.contract.release(nonpayee1),
'PaymentSplitter: account has no shares',
);

describe('Token', async function () {
it('reverts if no funds to claim', async function () {
await expectRevert(this.contract.release(this.token.address, payee1),
'PaymentSplitter: account is not due payment',
);
});
it('reverts if non-payee want to claim', async function () {
await this.token.transfer(this.contract.address, amount, { from: owner });
await expectRevert(this.contract.release(this.token.address, nonpayee1),
'PaymentSplitter: account has no shares',
);
});
});
});

it('distributes funds to payees', async function () {
await send.ether(payer1, this.contract.address, amount);
describe('distributes funds to payees', async function () {
it('Ether', async function () {
await send.ether(payer1, this.contract.address, amount);

// receive funds
const initBalance = await balance.current(this.contract.address);
expect(initBalance).to.be.bignumber.equal(amount);

// distribute to payees

// receive funds
const initBalance = await balance.current(this.contract.address);
expect(initBalance).to.be.bignumber.equal(amount);
const tracker1 = await balance.tracker(payee1);
const { logs: logs1 } = await this.contract.release(payee1);
const profit1 = await tracker1.delta();
expect(profit1).to.be.bignumber.equal(ether('0.20'));
expectEvent.inLogs(logs1, 'PaymentReleased', { to: payee1, amount: profit1 });

// distribute to payees
const tracker2 = await balance.tracker(payee2);
const { logs: logs2 } = await this.contract.release(payee2);
const profit2 = await tracker2.delta();
expect(profit2).to.be.bignumber.equal(ether('0.10'));
expectEvent.inLogs(logs2, 'PaymentReleased', { to: payee2, amount: profit2 });

const tracker1 = await balance.tracker(payee1);
const { logs: logs1 } = await this.contract.release(payee1);
const profit1 = await tracker1.delta();
expect(profit1).to.be.bignumber.equal(ether('0.20'));
expectEvent.inLogs(logs1, 'PaymentReleased', { to: payee1, amount: profit1 });
const tracker3 = await balance.tracker(payee3);
const { logs: logs3 } = await this.contract.release(payee3);
const profit3 = await tracker3.delta();
expect(profit3).to.be.bignumber.equal(ether('0.70'));
expectEvent.inLogs(logs3, 'PaymentReleased', { to: payee3, amount: profit3 });

const tracker2 = await balance.tracker(payee2);
const { logs: logs2 } = await this.contract.release(payee2);
const profit2 = await tracker2.delta();
expect(profit2).to.be.bignumber.equal(ether('0.10'));
expectEvent.inLogs(logs2, 'PaymentReleased', { to: payee2, amount: profit2 });
// end balance should be zero
expect(await balance.current(this.contract.address)).to.be.bignumber.equal('0');

const tracker3 = await balance.tracker(payee3);
const { logs: logs3 } = await this.contract.release(payee3);
const profit3 = await tracker3.delta();
expect(profit3).to.be.bignumber.equal(ether('0.70'));
expectEvent.inLogs(logs3, 'PaymentReleased', { to: payee3, amount: profit3 });
// check correct funds released accounting
expect(await this.contract.totalReleased()).to.be.bignumber.equal(initBalance);
});

// end balance should be zero
expect(await balance.current(this.contract.address)).to.be.bignumber.equal('0');
it('Token', async function () {
expect(await this.token.balanceOf(payee1)).to.be.bignumber.equal('0');
expect(await this.token.balanceOf(payee2)).to.be.bignumber.equal('0');
expect(await this.token.balanceOf(payee3)).to.be.bignumber.equal('0');

// check correct funds released accounting
expect(await this.contract.totalReleased()).to.be.bignumber.equal(initBalance);
await this.token.transfer(this.contract.address, amount, { from: owner });

expectEvent(
await this.contract.release(this.token.address, payee1),
'ERC20PaymentReleased',
{ token: this.token.address, to: payee1, amount: ether('0.20') },
);

await this.token.transfer(this.contract.address, amount, { from: owner });

expectEvent(
await this.contract.release(this.token.address, payee1),
'ERC20PaymentReleased',
{ token: this.token.address, to: payee1, amount: ether('0.20') },
);

expectEvent(
await this.contract.release(this.token.address, payee2),
'ERC20PaymentReleased',
{ token: this.token.address, to: payee2, amount: ether('0.20') },
);

expectEvent(
await this.contract.release(this.token.address, payee3),
'ERC20PaymentReleased',
{ token: this.token.address, to: payee3, amount: ether('1.40') },
);

expect(await this.token.balanceOf(payee1)).to.be.bignumber.equal(ether('0.40'));
expect(await this.token.balanceOf(payee2)).to.be.bignumber.equal(ether('0.20'));
expect(await this.token.balanceOf(payee3)).to.be.bignumber.equal(ether('1.40'));
});
});
});
});

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