compound-finance · scott-silver · Apr 22, 2022 · Apr 14, 2022 · Apr 14, 2022 · Apr 14, 2022
diff --git a/contracts/CometExt.sol b/contracts/CometExt.sol
@@ -95,16 +95,6 @@ contract CometExt is CometCore {
         return string(symbol_);
     }
 
-    /**
-      * @notice Query the current base balance of an account
-      * @dev Note: does not update interest indices before calculating
-      * @param account The account whose balance to query
-      * @return The present day base balance of the account
-      */
-    function baseBalanceOf(address account) external view returns (int104) {
-        return presentValue(userBasic[account].principal);
-    }
-
     /**
      * @notice Query the current collateral balance of an account
      * @param account The account whose balance to query

diff --git a/contracts/CometInterface.sol b/contracts/CometInterface.sol
@@ -62,7 +62,6 @@ abstract contract CometInterface is CometCore, ERC20 {
     function getBorrowRate() virtual external view returns (uint64);
     function getUtilization() virtual external view returns (uint);
 
-    function baseBalanceOf(address account) virtual external view returns (int104);
     function collateralBalanceOf(address account, address asset) virtual external view returns (uint128);
     function borrowBalanceOf(address account) virtual external view returns (uint256);
     function baseTrackingAccrued(address account) virtual external view returns (uint64);

diff --git a/scenario/ConstraintScenario.ts b/scenario/ConstraintScenario.ts
@@ -56,14 +56,18 @@ scenario(
       albert: { $base: -100 }, // in units of asset, not wei
     },
   },
-  async ({ comet, actors }, world, context) => {
+  async ({ comet, actors }, _world, context) => {
     const { albert } = actors;
     const baseAssetAddress = await comet.baseToken();
     const baseAsset = context.getAssetByAddress(baseAssetAddress);
     const scale = (await comet.baseScale()).toBigInt();
 
     expect(await baseAsset.balanceOf(albert.address)).to.be.equal(100n * scale);
-    expectApproximately(await albert.getCometBaseBalance(), -100n * scale, 1n);
+    expectApproximately(
+      await albert.getCometBaseBalance(),
+      -100n * scale,
+      (scale / 1000000n) // .000001 units of asset
+    );
   }
 );
 

diff --git a/scenario/LiquidationScenario.ts b/scenario/LiquidationScenario.ts
@@ -12,7 +12,7 @@ timeElapsed = -liquidationMargin / (baseBalanceOf * price / baseScale) / (borrow
 */
 async function timeUntilUnderwater({comet, actor, fudgeFactor = 0n}: {comet: CometInterface, actor: CometActor, fudgeFactor?: bigint}): Promise<number> {
   const liquidationMargin = (await comet.getLiquidationMargin(actor.address)).toBigInt();
-  const baseBalanceOf = (await comet.baseBalanceOf(actor.address)).toBigInt();
+  const baseBalance = await actor.getCometBaseBalance();
   const basePrice = (await comet.getPrice(await comet.baseTokenPriceFeed())).toBigInt();
   const borrowRate = (await comet.getBorrowRate()).toBigInt();
   const baseScale = (await comet.baseScale()).toBigInt();
@@ -24,7 +24,7 @@ async function timeUntilUnderwater({comet, actor, fudgeFactor = 0n}: {comet: Com
 
   // XXX throw error if baseBalanceOf is positive and liquidationMargin is positive
   return Number((-liquidationMargin * factorScale * baseScale /
-          (baseBalanceOf * basePrice) /
+          (baseBalance * basePrice) /
           borrowRate) + fudgeFactor);
 }
 
@@ -132,8 +132,8 @@ scenario(
     expect(lp1.numAbsorbed.toNumber()).to.eq(lp0.numAbsorbed.toNumber() + 1);
     // XXX test approxSpend?
 
-    const baseBalance = (await comet.baseBalanceOf(albert.address)).toNumber();
-    expect(baseBalance).to.be.greaterThanOrEqual(0);
+    const baseBalance = await albert.getCometBaseBalance();
+    expect(Number(baseBalance)).to.be.greaterThanOrEqual(0);
 
     // clears out all of liquidated user's collateral
     const numAssets = await comet.numAssets();
@@ -150,8 +150,8 @@ scenario(
 // XXX Skipping temporarily because testnet is in a weird state where an EOA ('admin') still
 // has permission to withdraw Comet's collateral, while Timelock does not. This is because the
 // permission was set up in the initialize() function. There is currently no way to update this
-// permission in Comet, so a new function (e.g. `approveCometPermission`) needs to be created 
-// to allow governance to modify which addresses can withdraw assets from Comet's Comet balance. 
+// permission in Comet, so a new function (e.g. `approveCometPermission`) needs to be created
+// to allow governance to modify which addresses can withdraw assets from Comet's Comet balance.
 scenario.skip(
   'Comet#liquidation > governor can withdraw collateral after successful liquidation',
   {

diff --git a/scenario/WithdrawScenario.ts b/scenario/WithdrawScenario.ts
@@ -77,7 +77,7 @@ scenario(
 
     expect(await baseAsset.balanceOf(albert.address)).to.be.equal(0n);
     expect(await comet.balanceOf(albert.address)).to.be.equal(0n);
-    
+
     // Albert borrows 1 unit of base from Comet
     const txn = await albert.withdrawAsset({ asset: baseAsset.address, amount: 1n * scale });
 
@@ -166,7 +166,7 @@ scenario(
 
     expect(await baseAsset.balanceOf(betty.address)).to.be.equal(0n);
     expect(await comet.balanceOf(albert.address)).to.be.equal(0n);
-    
+
     await albert.allow(betty, true);
 
     // Betty borrows 1 unit of base using Albert's account
@@ -195,7 +195,7 @@ scenario(
     const baseAssetAddress = await comet.baseToken();
     const baseAsset = context.getAssetByAddress(baseAssetAddress);
     const scale = (await comet.baseScale()).toBigInt();
-    
+
     // Betty borrows 1 unit of base using Albert's account
     await expect(
       betty.withdrawAssetFrom({

diff --git a/scenario/constraints/CometBalanceConstraint.ts b/scenario/constraints/CometBalanceConstraint.ts
@@ -1,10 +1,11 @@
-import { Constraint, Scenario, Solution, World } from '../../plugins/scenario';
+import { Constraint, World } from '../../plugins/scenario';
 import { CometContext } from '../context/CometContext';
 import CometActor from '../context/CometActor';
 import { expect } from 'chai';
 import { Requirements } from './Requirements';
-import { exp, factorScale } from '../../test/helpers';
+import { baseBalanceOf, exp, factorScale } from '../../test/helpers';
 import { ComparativeAmount, ComparisonOp, getAssetFromName, parseAmount, max, min } from '../utils';
+import { BigNumber } from 'ethers';
 
 async function borrowBase(borrowActor: CometActor, toBorrowBase: bigint, world: World, context: CometContext) {
   const comet = await context.getComet();
@@ -77,7 +78,7 @@ export class CometBalanceConstraint<T extends CometContext, R extends Requiremen
                 toTransfer = max(exp(amount.val, decimals) - cometBalance, 0);
                 break;
               case ComparisonOp.LTE:
-                // `toTransfer` should not be positive        
+                // `toTransfer` should not be positive
                 toTransfer = min(exp(amount.val, decimals) - cometBalance, 0);
                 break;
               case ComparisonOp.GT:
@@ -136,21 +137,23 @@ export class CometBalanceConstraint<T extends CometContext, R extends Requiremen
           const amount = parseAmount(rawAmount);
           const decimals = await asset.token.decimals();
           const baseToken = await comet.baseToken();
-          let actualBalance;
-          let expectedBalance;
+          // Chai matchers (like `.to.be.at.most()`) only work for numbers and
+          // BigNumbers, so we convert from BigInt to BigNumber
+          let actualBalance: BigNumber;
+          let expectedBalance: BigNumber;
           if (asset.address === baseToken) {
-            actualBalance = await comet.baseBalanceOf(actor.address);
+            actualBalance = BigNumber.from(await baseBalanceOf(comet, actor.address));
             const baseIndexScale = (await comet.baseIndexScale()).toBigInt();
             let baseIndex;
             if (amount.val >= 0) {
               baseIndex = (await comet.totalsBasic()).baseSupplyIndex.toBigInt();
             } else {
               baseIndex = (await comet.totalsBasic()).baseBorrowIndex.toBigInt();
             }
-            expectedBalance = getExpectedBaseBalance(exp(amount.val, decimals), baseIndexScale, baseIndex);
+            expectedBalance = BigNumber.from(getExpectedBaseBalance(exp(amount.val, decimals), baseIndexScale, baseIndex));
           } else {
-            actualBalance = await comet.collateralBalanceOf(actor.address, asset.address);
-            expectedBalance = exp(amount.val, decimals);
+            actualBalance = BigNumber.from(await comet.collateralBalanceOf(actor.address, asset.address));
+            expectedBalance = BigNumber.from(exp(amount.val, decimals));
           }
           switch (amount.op) {
             case ComparisonOp.EQ:
@@ -159,7 +162,7 @@ export class CometBalanceConstraint<T extends CometContext, R extends Requiremen
             case ComparisonOp.GTE:
               expect(actualBalance).to.be.at.least(expectedBalance);
               break;
-            case ComparisonOp.LTE:        
+            case ComparisonOp.LTE:
               expect(actualBalance).to.be.at.most(expectedBalance);
               break;
             case ComparisonOp.GT:

diff --git a/scenario/context/CometActor.ts b/scenario/context/CometActor.ts
@@ -3,6 +3,7 @@ import { BigNumberish, Signature, ethers, ContractReceipt } from 'ethers';
 import { CometContext } from './CometContext';
 import { AddressLike, resolveAddress } from './Address';
 import { ERC20__factory } from '../../build/types';
+import { baseBalanceOf } from '../../test/helpers';
 
 const types = {
   Authorization: [
@@ -54,7 +55,7 @@ export default class CometActor {
 
   async getCometBaseBalance(): Promise<bigint> {
     let comet = await this.context.getComet();
-    return (await comet.baseBalanceOf(this.signer.address)).toBigInt();
+    return baseBalanceOf(comet, this.signer.address);
   }
 
   async sendEth(recipient: AddressLike, amount: number) {

diff --git a/test/comet-ext-test.ts b/test/comet-ext-test.ts
@@ -47,13 +47,6 @@ describe('CometExt', function () {
     });
   });
 
-  it('returns principal as baseBalanceOf', async () => {
-    await comet.setBasePrincipal(user.address, 100e6);
-
-    const baseBalanceOf = await comet.baseBalanceOf(user.address);
-    expect(baseBalanceOf).to.eq(200e6); // baseSupplyIndex = 2e15
-  });
-
   it('returns collateralBalance (in units of the collateral asset)', async () => {
     const { WETH } = tokens;
 

diff --git a/test/erc20-test.ts b/test/erc20-test.ts
@@ -1,4 +1,4 @@
-import { ethers, event, expect, makeProtocol, setTotalsBasic, wait } from './helpers';
+import { baseBalanceOf, ethers, event, expect, makeProtocol, setTotalsBasic, wait } from './helpers';
 
 describe('erc20', function () {
   it('has correct name', async () => {
@@ -69,7 +69,7 @@ describe('erc20', function () {
       users: [alice, bob],
     } = await makeProtocol();
 
-    expect(await comet.baseBalanceOf(bob.address)).to.eq(0);
+    expect(await baseBalanceOf(comet, bob.address)).to.eq(0n);
 
     await comet.setBasePrincipal(alice.address, 50e6);
     await setTotalsBasic(comet, {
@@ -78,8 +78,8 @@ describe('erc20', function () {
 
     const tx = await wait(comet.connect(alice).transfer(bob.address, 100e6));
 
-    expect(await comet.baseBalanceOf(alice.address)).to.eq(0);
-    expect(await comet.baseBalanceOf(bob.address)).to.eq(100e6);
+    expect(await baseBalanceOf(comet, alice.address)).to.eq(0n);
+    expect(await baseBalanceOf(comet, bob.address)).to.eq(BigInt(100e6));
     expect(event(tx, 0)).to.be.deep.equal({
       Transfer: {
         from: alice.address,
@@ -103,8 +103,8 @@ describe('erc20', function () {
 
       await comet.connect(alice).transferFrom(alice.address, bob.address, 100e6)
 
-      expect(await comet.baseBalanceOf(alice.address)).to.eq(0);
-      expect(await comet.baseBalanceOf(bob.address)).to.eq(100e6);
+      expect(await baseBalanceOf(comet, alice.address)).to.eq(0n);
+      expect(await baseBalanceOf(comet, bob.address)).to.eq(BigInt(100e6));
     });
 
     it('reverts ERC20 transferFrom without approval', async () => {
@@ -139,8 +139,8 @@ describe('erc20', function () {
       // bob can now transfer funds from alice
       await comet.connect(bob).transferFrom(alice.address, bob.address, 100e6);
 
-      expect(await comet.baseBalanceOf(alice.address)).to.eq(0);
-      expect(await comet.baseBalanceOf(bob.address)).to.eq(100e6);
+      expect(await baseBalanceOf(comet, alice.address)).to.eq(0n);
+      expect(await baseBalanceOf(comet, bob.address)).to.eq(BigInt(100e6));
     });
 
     it('reverts ERC20 transferFrom with revoked approval', async () => {

diff --git a/test/helpers.ts b/test/helpers.ts
@@ -28,6 +28,7 @@ import {
   Configurator,
   Configurator__factory,
   CometHarnessInterface,
+  CometInterface,
 } from '../build/types';
 import { BigNumber } from 'ethers';
 import { TransactionReceipt, TransactionResponse } from '@ethersproject/abstract-provider';
@@ -427,15 +428,6 @@ export async function makeConfigurator(opts: ProtocolOpts = {}): Promise<Configu
   };
 }
 
-type Portfolio = {
-  internal: {
-    [symbol: string]: BigInt,
-  },
-  external: {
-    [symbol: string]: BigInt,
-  }
-}
-
 export async function makeRewards(opts: RewardsOpts = {}): Promise<Rewards> {
   const signers = await ethers.getSigners();
 
@@ -479,8 +471,23 @@ export function objectify(arrayObject) {
   return obj;
 }
 
+export async function baseBalanceOf(comet: CometInterface, account: string): Promise<bigint> {
+  const balanceOf = await comet.balanceOf(account);
+  const borrowBalanceOf = await comet.borrowBalanceOf(account);
+  return balanceOf.sub(borrowBalanceOf).toBigInt();
+}
+
+type Portfolio = {
+  internal: {
+    [symbol: string]: BigInt,
+  },
+  external: {
+    [symbol: string]: BigInt,
+  }
+}
+
 export async function portfolio({ comet, base, tokens }, account): Promise<Portfolio>  {
-  const internal = { [base]: BigInt(await comet.baseBalanceOf(account)) };
+  const internal = { [base]: await baseBalanceOf(comet, account) };
   const external = { [base]: BigInt(await tokens[base].balanceOf(account)) };
   for (const symbol in tokens) {
     if (symbol != base) {

diff --git a/test/transfer-test.ts b/test/transfer-test.ts
@@ -1,5 +1,4 @@
-import { event, expect, exp, makeProtocol, portfolio, setTotalsBasic, wait } from './helpers';
-import { BigNumber } from "ethers";
+import { baseBalanceOf, event, expect, exp, makeProtocol, portfolio, setTotalsBasic, wait } from './helpers';
 
 describe('transfer', function () {
   it('transfers base from sender if the asset is base', async () => {
@@ -148,7 +147,7 @@ describe('transfer', function () {
 
     const t1 = await comet.totalsBasic();
 
-    expect(await comet.baseBalanceOf(alice.address)).to.eq(-100e6);
+    expect(await baseBalanceOf(comet, alice.address)).to.eq(BigInt(-100e6));
   });
 
   it('cant borrow less than the minimum', async () => {

diff --git a/test/withdraw-test.ts b/test/withdraw-test.ts
@@ -1,6 +1,5 @@
-import { BigNumber } from "ethers";
 import { EvilToken, EvilToken__factory, FaucetToken } from '../build/types';
-import { ethers, event, expect, exp, makeProtocol, portfolio, ReentryAttack, setTotalsBasic, wait } from './helpers';
+import { baseBalanceOf, ethers, event, expect, exp, makeProtocol, portfolio, ReentryAttack, setTotalsBasic, wait } from './helpers';
 
 describe('withdrawTo', function () {
   it('withdraws base from sender if the asset is base', async () => {
@@ -207,7 +206,7 @@ describe('withdrawTo', function () {
     const t1 = await comet.totalsBasic();
     const baseIndexScale = await comet.baseIndexScale();
 
-    expect(await comet.baseBalanceOf(alice.address)).to.eq(-1e6);
+    expect(await baseBalanceOf(comet, alice.address)).to.eq(BigInt(-1e6));
     expect(await USDC.balanceOf(bob.address)).to.eq(1e6);
   });
 });
@@ -332,9 +331,9 @@ describe('withdraw', function () {
 
       // no USDC transferred
       expect(await USDC.balanceOf(comet.address)).to.eq(100e6);
-      expect(await comet.baseBalanceOf(alice.address)).to.eq(0);
+      expect(await baseBalanceOf(comet, alice.address)).to.eq(0n);
       expect(await USDC.balanceOf(alice.address)).to.eq(0);
-      expect(await comet.baseBalanceOf(bob.address)).to.eq(0);
+      expect(await baseBalanceOf(comet, bob.address)).to.eq(0n);
       expect(await USDC.balanceOf(bob.address)).to.eq(0);
     });
 
@@ -379,9 +378,9 @@ describe('withdraw', function () {
 
       // no USDC transferred
       expect(await USDC.balanceOf(comet.address)).to.eq(100e6);
-      expect(await comet.baseBalanceOf(alice.address)).to.eq(0);
+      expect(await baseBalanceOf(comet, alice.address)).to.eq(0n);
       expect(await USDC.balanceOf(alice.address)).to.eq(0);
-      expect(await comet.baseBalanceOf(bob.address)).to.eq(0);
+      expect(await baseBalanceOf(comet, bob.address)).to.eq(0n);
       expect(await USDC.balanceOf(bob.address)).to.eq(0);
     });
   });