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Add internal overrideable _flashFee in ERC20FlashMint (#3551)

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Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: Francisco <frangio.1@gmail.com>
This commit is contained in:
Nirban Chakraborty
2022-07-22 23:14:58 +05:30
committed by GitHub
parent 6e8d885ca7
commit d1b1e17d23
4 changed files with 29 additions and 18 deletions
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1
CHANGELOG.md
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@ -11,6 +11,7 @@
* `ERC721`: optimize burn by making approval clearing implicit instead of emitting an event. ([#3538](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3538))
* `ReentrancyGuard`: Reduce code size impact of the modifier by using internal functions. ([#3515](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3515))
* `SafeCast`: optimize downcasting of signed integers. ([#3565](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3565))
* `ERC20FlashMint`: add an internal `_flashFee` function for overriding. ([#3551](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3551))
### Compatibility Note

3
contracts/mocks/ERC20FlashMintMock.sol
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@ -25,8 +25,7 @@ contract ERC20FlashMintMock is ERC20FlashMint {
_flashFeeAmount = amount;
}
function flashFee(address token, uint256 amount) public view virtual override returns (uint256) {
super.flashFee(token, amount);
function _flashFee(address, uint256) internal view override returns (uint256) {
return _flashFeeAmount;
}

11
contracts/token/ERC20/extensions/ERC20FlashMint.sol
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@ -38,7 +38,18 @@ abstract contract ERC20FlashMint is ERC20, IERC3156FlashLender {
*/
function flashFee(address token, uint256 amount) public view virtual override returns (uint256) {
require(token == address(this), "ERC20FlashMint: wrong token");
return _flashFee(token, amount);
}
/**
* @dev Returns the fee applied when doing flash loans. This function calls the {flashFee} function which returns the fee applied when doing flash loans.
* @param token The token to be flash loaned.
* @param amount The amount of tokens to be loaned.
* @return The fees applied to the corresponding flash loan.
*/
function _flashFee(address token, uint256 amount) internal view virtual returns (uint256) {
// silence warning about unused variable without the addition of bytecode.
token;
amount;
return 0;
}

32
test/token/ERC20/extensions/ERC20FlashMint.test.js
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@ -8,7 +8,7 @@ const ERC20FlashMintMock = artifacts.require('ERC20FlashMintMock');
const ERC3156FlashBorrowerMock = artifacts.require('ERC3156FlashBorrowerMock');
contract('ERC20FlashMint', function (accounts) {
const [ initialHolder, other, anotherAccount ] = accounts;
const [initialHolder, other, anotherAccount] = accounts;
const name = 'My Token';
const symbol = 'MTKN';
@ -61,7 +61,7 @@ contract('ERC20FlashMint', function (accounts) {
expect(await this.token.allowance(receiver.address, this.token.address)).to.be.bignumber.equal('0');
});
it ('missing return value', async function () {
it('missing return value', async function () {
const receiver = await ERC3156FlashBorrowerMock.new(false, true);
await expectRevert(
this.token.flashLoan(receiver.address, this.token.address, loanAmount, '0x'),
@ -69,7 +69,7 @@ contract('ERC20FlashMint', function (accounts) {
);
});
it ('missing approval', async function () {
it('missing approval', async function () {
const receiver = await ERC3156FlashBorrowerMock.new(true, false);
await expectRevert(
this.token.flashLoan(receiver.address, this.token.address, loanAmount, '0x'),
@ -77,7 +77,7 @@ contract('ERC20FlashMint', function (accounts) {
);
});
it ('unavailable funds', async function () {
it('unavailable funds', async function () {
const receiver = await ERC3156FlashBorrowerMock.new(true, true);
const data = this.token.contract.methods.transfer(other, 10).encodeABI();
await expectRevert(
@ -86,7 +86,7 @@ contract('ERC20FlashMint', function (accounts) {
);
});
it ('more than maxFlashLoan', async function () {
it('more than maxFlashLoan', async function () {
const receiver = await ERC3156FlashBorrowerMock.new(true, true);
const data = this.token.contract.methods.transfer(other, 10).encodeABI();
// _mint overflow reverts using a panic code. No reason string.
@ -96,8 +96,8 @@ contract('ERC20FlashMint', function (accounts) {
describe('custom flash fee & custom fee receiver', function () {
const receiverInitialBalance = new BN(200000);
const flashFee = new BN(5000);
beforeEach('init reciever balance & set flash fee',async function () {
beforeEach('init reciever balance & set flash fee', async function () {
this.receiver = await ERC3156FlashBorrowerMock.new(true, true);
const receipt = await this.token.mint(this.receiver.address, receiverInitialBalance);
await expectEvent(receipt, 'Transfer', { from: ZERO_ADDRESS, to: this.receiver.address, value: receiverInitialBalance });
@ -106,13 +106,13 @@ contract('ERC20FlashMint', function (accounts) {
await this.token.setFlashFee(flashFee);
expect(await this.token.flashFee(this.token.address, loanAmount)).to.be.bignumber.equal(flashFee);
});
it('default flash fee receiver', async function () {
const { tx } = await this.token.flashLoan(this.receiver.address, this.token.address, loanAmount, '0x');
await expectEvent.inTransaction(tx, this.token, 'Transfer', { from: ZERO_ADDRESS, to: this.receiver.address, value: loanAmount });
await expectEvent.inTransaction(tx, this.token, 'Transfer', { from: this.receiver.address, to: ZERO_ADDRESS, value: loanAmount.add (flashFee)});
await expectEvent.inTransaction(tx, this.receiver, 'BalanceOf', { token: this.token.address, account: this.receiver.address, value: receiverInitialBalance.add(loanAmount) });
await expectEvent.inTransaction(tx, this.receiver, 'TotalSupply', { token: this.token.address, value: initialSupply.add (receiverInitialBalance).add(loanAmount) });
await expectEvent.inTransaction(tx, this.token, 'Transfer', { from: this.receiver.address, to: ZERO_ADDRESS, value: loanAmount.add(flashFee) });
await expectEvent.inTransaction(tx, this.receiver, 'BalanceOf', { token: this.token.address, account: this.receiver.address, value: receiverInitialBalance.add(loanAmount) });
await expectEvent.inTransaction(tx, this.receiver, 'TotalSupply', { token: this.token.address, value: initialSupply.add(receiverInitialBalance).add(loanAmount) });
expect(await this.token.totalSupply()).to.be.bignumber.equal(initialSupply.add(receiverInitialBalance).sub(flashFee));
expect(await this.token.balanceOf(this.receiver.address)).to.be.bignumber.equal(receiverInitialBalance.sub(flashFee));
@ -124,15 +124,15 @@ contract('ERC20FlashMint', function (accounts) {
const flashFeeReceiverAddress = anotherAccount;
await this.token.setFlashFeeReceiver(flashFeeReceiverAddress);
expect(await this.token.flashFeeReceiver()).to.be.eq(flashFeeReceiverAddress);
expect(await this.token.balanceOf(flashFeeReceiverAddress)).to.be.bignumber.equal('0');
const { tx } = await this.token.flashLoan(this.receiver.address, this.token.address, loanAmount, '0x');
await expectEvent.inTransaction(tx, this.token, 'Transfer', { from: ZERO_ADDRESS, to: this.receiver.address, value: loanAmount });
await expectEvent.inTransaction(tx, this.token, 'Transfer', { from: this.receiver.address, to: ZERO_ADDRESS, value: loanAmount });
await expectEvent.inTransaction(tx, this.token, 'Transfer', { from: this.receiver.address, to: flashFeeReceiverAddress, value: flashFee });
await expectEvent.inTransaction(tx, this.receiver, 'BalanceOf', { token: this.token.address, account: this.receiver.address, value: receiverInitialBalance.add(loanAmount) });
await expectEvent.inTransaction(tx, this.receiver, 'TotalSupply', { token: this.token.address, value: initialSupply.add (receiverInitialBalance).add(loanAmount) });
await expectEvent.inTransaction(tx, this.token, 'Transfer', { from: this.receiver.address, to: flashFeeReceiverAddress, value: flashFee });
await expectEvent.inTransaction(tx, this.receiver, 'BalanceOf', { token: this.token.address, account: this.receiver.address, value: receiverInitialBalance.add(loanAmount) });
await expectEvent.inTransaction(tx, this.receiver, 'TotalSupply', { token: this.token.address, value: initialSupply.add(receiverInitialBalance).add(loanAmount) });
expect(await this.token.totalSupply()).to.be.bignumber.equal(initialSupply.add(receiverInitialBalance));
expect(await this.token.balanceOf(this.receiver.address)).to.be.bignumber.equal(receiverInitialBalance.sub(flashFee));