Fix for #315 (v2 Polygon)

contracts/protocol/libraries/logic/ReserveLogic.sol

@@ -108,6 +108,12 @@ library ReserveLogic {
    * @param reserve the reserve object
    **/
   function updateState(DataTypes.ReserveData storage reserve) internal {
+    // If time didn't pass since last stored timestamp, skip state update
+    //solium-disable-next-line
+    if (reserve.lastUpdateTimestamp == uint40(block.timestamp)) {
+      return;
+    }
+
     uint256 scaledVariableDebt =
       IVariableDebtToken(reserve.variableDebtTokenAddress).scaledTotalSupply();
     uint256 previousVariableBorrowIndex = reserve.variableBorrowIndex;
@@ -343,27 +349,27 @@ library ReserveLogic {
     uint256 newLiquidityIndex = liquidityIndex;
     uint256 newVariableBorrowIndex = variableBorrowIndex;
 
-    //only cumulating if there is any income being produced
+    // Only cumulating on the supply side if there is any income being produced
+    // The case of Reserve Factor 100% is not a problem (currentLiquidityRate == 0),
+    // as liquidity index should not be updated
     if (currentLiquidityRate > 0) {
       uint256 cumulatedLiquidityInterest =
         MathUtils.calculateLinearInterest(currentLiquidityRate, timestamp);
       newLiquidityIndex = cumulatedLiquidityInterest.rayMul(liquidityIndex);
       require(newLiquidityIndex <= type(uint128).max, Errors.RL_LIQUIDITY_INDEX_OVERFLOW);
-
       reserve.liquidityIndex = uint128(newLiquidityIndex);
+    }
 
-      //as the liquidity rate might come only from stable rate loans, we need to ensure
-      //that there is actual variable debt before accumulating
-      if (scaledVariableDebt != 0) {
-        uint256 cumulatedVariableBorrowInterest =
-          MathUtils.calculateCompoundedInterest(reserve.currentVariableBorrowRate, timestamp);
-        newVariableBorrowIndex = cumulatedVariableBorrowInterest.rayMul(variableBorrowIndex);
-        require(
-          newVariableBorrowIndex <= type(uint128).max,
-          Errors.RL_VARIABLE_BORROW_INDEX_OVERFLOW
-        );
-        reserve.variableBorrowIndex = uint128(newVariableBorrowIndex);
-      }
+    // Variable borrow side only gets updated if there is any accrual of variable debt
+    if (scaledVariableDebt > 0) {
+      uint256 cumulatedVariableBorrowInterest =
+        MathUtils.calculateCompoundedInterest(reserve.currentVariableBorrowRate, timestamp);
+      newVariableBorrowIndex = cumulatedVariableBorrowInterest.rayMul(variableBorrowIndex);
+      require(
+        newVariableBorrowIndex <= type(uint128).max,
+        Errors.RL_VARIABLE_BORROW_INDEX_OVERFLOW
+      );
+      reserve.variableBorrowIndex = uint128(newVariableBorrowIndex);
     }
 
     //solium-disable-next-line

package.json

@@ -25,6 +25,7 @@
     "test-amm": "npm run compile && TS_NODE_TRANSPILE_ONLY=1 hardhat test ./test-suites/test-amm/*.spec.ts",
     "test-amm-scenarios": "npm run compile && TS_NODE_TRANSPILE_ONLY=1 hardhat test ./test-suites/test-amm/__setup.spec.ts test-suites/test-amm/scenario.spec.ts",
     "test-scenarios": "npm run compile && npx hardhat test test-suites/test-aave/__setup.spec.ts test-suites/test-aave/scenario.spec.ts",
+    "test-reserve-factor": "npm run compile && npx hardhat test test-suites/test-aave/__setup.spec.ts test-suites/test-aave/reserve-factor.spec.ts",
     "test-subgraph:scenarios": "npm run compile && hardhat --network hardhatevm_docker test test-suites/test-aave/__setup.spec.ts test-suites/test-aave/subgraph-scenarios.spec.ts",
     "test:main:check-list": "npm run compile && FORK=main TS_NODE_TRANSPILE_ONLY=1 hardhat test  test-suites/test-aave/__setup.spec.ts test-suites/test-aave/mainnet/check-list.spec.ts",
     "dev:coverage": "buidler compile --force && buidler coverage --network coverage",

test-suites/test-aave/reserve-factor.spec.ts

@@ -0,0 +1,192 @@
+import BigNumber from 'bignumber.js';
+
+import { DRE, increaseTime } from '../../helpers/misc-utils';
+import { APPROVAL_AMOUNT_LENDING_POOL, oneEther } from '../../helpers/constants';
+import { convertToCurrencyDecimals } from '../../helpers/contracts-helpers';
+import { makeSuite, TestEnv } from './helpers/make-suite';
+import { RateMode } from '../../helpers/types';
+import { ConfigNames, getTreasuryAddress, loadPoolConfig } from '../../helpers/configuration';
+
+const chai = require('chai');
+
+const { expect } = chai;
+
+// Setup function to have 1 user with DAI deposits, and another user with WETH collateral
+// and DAI borrowings at an indicated borrowing mode
+const setupPositions = async (testEnv: TestEnv, borrowingMode: RateMode) => {
+  const { dai, weth, users, pool, oracle } = testEnv;
+  const depositor = users[0];
+  const borrower = users[1];
+
+  // mints DAI to depositor
+  await dai.connect(depositor.signer).mint(await convertToCurrencyDecimals(dai.address, '2000'));
+
+  // approve protocol to access depositor wallet
+  await dai.connect(depositor.signer).approve(pool.address, APPROVAL_AMOUNT_LENDING_POOL);
+
+  // user 1 deposits 1000 DAI
+  const amountDAItoDeposit = await convertToCurrencyDecimals(dai.address, '1000');
+
+  await pool
+    .connect(depositor.signer)
+    .deposit(dai.address, amountDAItoDeposit, depositor.address, '0');
+  // user 2 deposits 1 ETH
+  const amountETHtoDeposit = await convertToCurrencyDecimals(weth.address, '1');
+
+  // mints WETH to borrower
+  await weth.connect(borrower.signer).mint(await convertToCurrencyDecimals(weth.address, '1000'));
+
+  // approve protocol to access the borrower wallet
+  await weth.connect(borrower.signer).approve(pool.address, APPROVAL_AMOUNT_LENDING_POOL);
+
+  await pool
+    .connect(borrower.signer)
+    .deposit(weth.address, amountETHtoDeposit, borrower.address, '0');
+
+  //user 2 borrows
+
+  const userGlobalData = await pool.getUserAccountData(borrower.address);
+  const daiPrice = await oracle.getAssetPrice(dai.address);
+
+  const amountDAIToBorrow = await convertToCurrencyDecimals(
+    dai.address,
+    new BigNumber(userGlobalData.availableBorrowsETH.toString())
+      .div(daiPrice.toString())
+      .multipliedBy(0.95)
+      .toFixed(0)
+  );
+
+  await pool
+    .connect(borrower.signer)
+    .borrow(dai.address, amountDAIToBorrow, borrowingMode, '0', borrower.address);
+};
+
+makeSuite('LendingPool Reserve Factor 100%. Only variable borrowings', (testEnv) => {
+  before('Before LendingPool Reserve Factor accrual: set config', () => {
+    BigNumber.config({ DECIMAL_PLACES: 0, ROUNDING_MODE: BigNumber.ROUND_DOWN });
+  });
+
+  after('After LendingPool Reserve Factor accrual: reset config', () => {
+    BigNumber.config({ DECIMAL_PLACES: 20, ROUNDING_MODE: BigNumber.ROUND_HALF_UP });
+  });
+
+  it('Validates that variable borrow index accrue, liquidity index not, and the Collector receives aTokens after interest accrues', async () => {
+    const { configurator, dai, users, pool, aDai } = testEnv;
+
+    await setupPositions(testEnv, RateMode.Variable);
+
+    // Set the RF to 100%
+    await configurator.setReserveFactor(dai.address, '10000');
+
+    const depositor = users[0];
+
+    const collectorAddress = await getTreasuryAddress(loadPoolConfig(ConfigNames.Aave));
+
+    const collectorADAIBalanceBefore = await aDai.scaledBalanceOf(collectorAddress);
+
+    const reserveDataBefore = await pool.getReserveData(dai.address);
+
+    await increaseTime(10000);
+
+    // Deposit to "settle" the liquidity index accrual from pre-RF increase to 100%
+    await pool
+      .connect(depositor.signer)
+      .deposit(
+        dai.address,
+        await convertToCurrencyDecimals(dai.address, '1'),
+        depositor.address,
+        '0'
+      );
+
+    const reserveDataAfter1 = await pool.getReserveData(dai.address);
+    const collectorADAIBalanceAfter1 = await aDai.balanceOf(collectorAddress);
+
+    expect(reserveDataAfter1.variableBorrowIndex).to.be.gt(reserveDataBefore.variableBorrowIndex);
+    expect(collectorADAIBalanceAfter1).to.be.gt(collectorADAIBalanceBefore);
+    expect(reserveDataAfter1.liquidityIndex).to.be.gt(reserveDataBefore.liquidityIndex);
+
+    await increaseTime(10000);
+
+    // "Clean" update, that should not increase the liquidity index, only variable borrow
+    await pool
+      .connect(depositor.signer)
+      .deposit(
+        dai.address,
+        await convertToCurrencyDecimals(dai.address, '1'),
+        depositor.address,
+        '0'
+      );
+
+    const reserveDataAfter2 = await pool.getReserveData(dai.address);
+    const collectorADAIBalanceAfter2 = await aDai.balanceOf(collectorAddress);
+
+    expect(reserveDataAfter2.variableBorrowIndex).to.be.gt(reserveDataAfter1.variableBorrowIndex);
+    expect(collectorADAIBalanceAfter2).to.be.gt(collectorADAIBalanceAfter1);
+    expect(reserveDataAfter2.liquidityIndex).to.be.eq(reserveDataAfter1.liquidityIndex);
+  });
+});
+
+makeSuite('LendingPool Reserve Factor 100%. Only stable borrowings', (testEnv) => {
+  before('Before LendingPool Reserve Factor accrual: set config', () => {
+    BigNumber.config({ DECIMAL_PLACES: 0, ROUNDING_MODE: BigNumber.ROUND_DOWN });
+  });
+
+  after('After LendingPool Reserve Factor accrual: reset config', () => {
+    BigNumber.config({ DECIMAL_PLACES: 20, ROUNDING_MODE: BigNumber.ROUND_HALF_UP });
+  });
+
+  it('Validates that neither variable borrow index nor liquidity index increase, but the Collector receives aTokens after interest accrues', async () => {
+    const { configurator, dai, users, pool, aDai } = testEnv;
+
+    await setupPositions(testEnv, RateMode.Stable);
+
+    // Set the RF to 100%
+    await configurator.setReserveFactor(dai.address, '10000');
+
+    const depositor = users[0];
+
+    const collectorAddress = await getTreasuryAddress(loadPoolConfig(ConfigNames.Aave));
+
+    const collectorADAIBalanceBefore = await aDai.scaledBalanceOf(collectorAddress);
+
+    const reserveDataBefore = await pool.getReserveData(dai.address);
+
+    await increaseTime(10000);
+
+    // Deposit to "settle" the liquidity index accrual from pre-RF increase to 100%
+    await pool
+      .connect(depositor.signer)
+      .deposit(
+        dai.address,
+        await convertToCurrencyDecimals(dai.address, '1'),
+        depositor.address,
+        '0'
+      );
+
+    const reserveDataAfter1 = await pool.getReserveData(dai.address);
+    const collectorADAIBalanceAfter1 = await aDai.balanceOf(collectorAddress);
+
+    expect(reserveDataAfter1.variableBorrowIndex).to.be.eq(reserveDataBefore.variableBorrowIndex);
+    expect(collectorADAIBalanceAfter1).to.be.gt(collectorADAIBalanceBefore);
+    expect(reserveDataAfter1.liquidityIndex).to.be.gt(reserveDataBefore.liquidityIndex);
+
+    await increaseTime(10000);
+
+    // "Clean" update, that should not increase the liquidity index, only variable borrow
+    await pool
+      .connect(depositor.signer)
+      .deposit(
+        dai.address,
+        await convertToCurrencyDecimals(dai.address, '1'),
+        depositor.address,
+        '0'
+      );
+
+    const reserveDataAfter2 = await pool.getReserveData(dai.address);
+    const collectorADAIBalanceAfter2 = await aDai.balanceOf(collectorAddress);
+
+    expect(reserveDataAfter2.variableBorrowIndex).to.be.eq(reserveDataAfter1.variableBorrowIndex);
+    expect(collectorADAIBalanceAfter2).to.be.gt(collectorADAIBalanceAfter1);
+    expect(reserveDataAfter2.liquidityIndex).to.be.eq(reserveDataAfter1.liquidityIndex);
+  });
+});