Merge pull request #284 from yieldprotocol/fix/no-fee-base-is-ilk

fix: don't charge a borrowing fee if base == ilk

contracts/Ladle.sol

@@ -336,7 +336,8 @@ contract Ladle is LadleStorage, AccessControl() {
         if (art != 0) series = getSeries(vault.seriesId);
 
         int128 fee;
-        if (art > 0) fee = ((series.maturity - block.timestamp) * uint256(int256(art)).wmul(borrowingFee)).i128();
+        if (art > 0 && vault.ilkId != series.baseId && borrowingFee != 0)
+            fee = ((series.maturity - block.timestamp) * uint256(int256(art)).wmul(borrowingFee)).i128();
 
         // Update accounting
         cauldron.pour(vaultId, ink, art + fee);
@@ -474,7 +475,8 @@ contract Ladle is LadleStorage, AccessControl() {
             fyToken.burn(address(fyToken), (base * loan) - newDebt);    // Burn the surplus
         }
 
-        newDebt += ((newSeries.maturity - block.timestamp) * uint256(newDebt).wmul(borrowingFee)).u128();  // Add borrowing fee, also stops users form rolling to a mature series
+        if (vault.ilkId != newSeries.baseId && borrowingFee != 0)
+            newDebt += ((newSeries.maturity - block.timestamp) * uint256(newDebt).wmul(borrowingFee)).u128();  // Add borrowing fee, also stops users form rolling to a mature series
 
         (vault,) = cauldron.roll(vaultId, newSeriesId, newDebt.i128() - balances.art.i128()); // Change the series and debt for the vault
 

hardhat.config.ts

@@ -87,7 +87,7 @@ module.exports = {
     settings: {
       optimizer: {
         enabled: true,
-        runs: 2500,
+        runs: 1500,
       }
     }
   },

test/061_ladle_pour.ts

@@ -3,6 +3,7 @@ import { SignerWithAddress } from '@nomiclabs/hardhat-ethers/dist/src/signer-wit
 import { constants } from '@yield-protocol/utils-v2'
 const { WAD } = constants
 import { ETH } from '../src/constants'
+import { getLastVaultId } from '../src/helpers'
 
 import { Cauldron } from '../typechain/Cauldron'
 import { Join } from '../typechain/Join'
@@ -49,6 +50,7 @@ describe('Ladle - pour', function () {
   const ilkId = ETH
   const seriesId = ethers.utils.hexlify(ethers.utils.randomBytes(6))
   let vaultId: string
+  let baseVaultId: string
 
   beforeEach(async () => {
     env = await loadFixture(fixture)
@@ -62,6 +64,8 @@ describe('Ladle - pour', function () {
 
     vaultId = (env.vaults.get(seriesId) as Map<string, string>).get(ilkId) as string
     await cauldron.setDebtLimits(baseId, ilkId, WAD.mul(2).div(1000000), 1000000, 6)
+
+    baseVaultId = (env.vaults.get(seriesId) as Map<string, string>).get(baseId) as string
   })
 
   it('only the vault owner can manage its collateral', async () => {
@@ -79,6 +83,7 @@ describe('Ladle - pour', function () {
   describe('with posted collateral', async () => {
     beforeEach(async () => {
       await ladle.pour(vaultId, owner, WAD, 0)
+      await ladle.pour(baseVaultId, owner, WAD, 0)
     })
 
     it('users can pour to withdraw collateral', async () => {
@@ -119,6 +124,14 @@ describe('Ladle - pour', function () {
       expect(await fyToken.balanceOf(owner)).to.equal(WAD)
       expect((await cauldron.balances(vaultId)).art).to.equal(WAD.add(appliedFee))
     })
+
+    it('except if baseId == ilkId', async () => {
+      const fee = WAD.div(1000000000) // 0.000000 001% wei/second
+      await ladle.setFee(fee)
+      await ladle.pour(baseVaultId, owner, 0, WAD)
+      expect(await fyToken.balanceOf(owner)).to.equal(WAD)
+      expect((await cauldron.balances(baseVaultId)).art).to.equal(WAD)
+    })
   })
 
   it('users can pour to post collateral and borrow fyToken', async () => {

test/065_ladle_roll.ts

@@ -52,8 +52,9 @@ describe('Ladle - roll', function () {
   const baseId = ethers.utils.hexlify(ethers.utils.randomBytes(6))
   const ilkId = ETH
   const seriesId = ethers.utils.hexlify(ethers.utils.randomBytes(6))
-  const vaultId = ethers.utils.hexlify(ethers.utils.randomBytes(12))
   const otherSeriesId = ethers.utils.hexlify(ethers.utils.randomBytes(6))
+  let vaultId: string
+  let baseVaultId: string
 
   beforeEach(async () => {
     env = await loadFixture(fixture)
@@ -65,8 +66,11 @@ describe('Ladle - roll', function () {
     otherFYToken = env.series.get(otherSeriesId) as FYToken
 
     // ==== Set testing environment ====
-    await cauldron.build(owner, vaultId, seriesId, ilkId)
+    vaultId = (env.vaults.get(seriesId) as Map<string, string>).get(ilkId) as string
     await ladle.pour(vaultId, owner, WAD, WAD)
+
+    baseVaultId = (env.vaults.get(seriesId) as Map<string, string>).get(baseId) as string
+    await ladle.pour(baseVaultId, owner, WAD, WAD)
   })
 
   it('does not allow rolling vaults other than to the vault owner', async () => {
@@ -90,10 +94,22 @@ describe('Ladle - roll', function () {
     const preFeeDebt = WAD.mul(105).div(100)
     const appliedFee = (await otherFYToken.maturity()).sub(timestamp).mul(preFeeDebt).mul(fee).div(WAD)
 
-    expect(await fyToken.balanceOf(owner)).to.equal(WAD)
+    expect(await fyToken.balanceOf(owner)).to.equal(WAD.mul(2))
     expect((await cauldron.balances(vaultId)).art).to.equal(preFeeDebt.add(appliedFee))
   })
 
+  it('except if base == ilk', async () => {
+    await ladle.pour(baseVaultId, owner, WAD.mul(5).div(100), 0) // The exchange rate is 1:1, but YieldSpace charges a 5%
+
+    const fee = WAD.div(1000000000) // 0.000000 001% wei/second
+    await ladle.setFee(fee)
+    await ladle.roll(baseVaultId, otherSeriesId, loan, MAX)
+    const preFeeDebt = WAD.mul(105).div(100)
+
+    expect(await fyToken.balanceOf(owner)).to.equal(WAD.mul(2))
+    expect((await cauldron.balances(baseVaultId)).art).to.equal(preFeeDebt)
+  })
+
   describe('after maturity', async () => {
     beforeEach(async () => {
       await ethers.provider.send('evm_mine', [(await fyToken.maturity()).toNumber()])

test/shared/fixtures.ts

@@ -278,6 +278,10 @@ export class YieldEnvironment {
     await usdcAggregator.set(WAD.div(2))
     sources.set(USDC, usdcAggregator)
 
+    const baseAggregator = (await deployContract(owner, ChainlinkAggregatorV3MockArtifact)) as ISourceMock
+    await baseAggregator.set(WAD)
+    sources.set(baseId, baseAggregator)
+
     // ==== Libraries ====
     const SafeERC20NamerFactory = await ethers.getContractFactory('SafeERC20Namer')
     const safeERC20NamerLibrary = ((await SafeERC20NamerFactory.deploy()) as unknown) as SafeERC20Namer
@@ -359,7 +363,8 @@ export class YieldEnvironment {
 
     // ==== Make ilkIds the ilks, creating spot oracles and settting debt limits ====
     const ratio = 1000000 //  1000000 == 100% collateralization ratio
-    for (let ilkId of ilkIds) {
+    for (let ilkId of assetIds) {
+      // Including ilkId == baseId
       const spotSource = sources.get(ilkId) as ISourceMock
       const base = assets.get(baseId) as ERC20Mock
       const ilk = assets.get(ilkId) as ERC20Mock
@@ -376,7 +381,7 @@ export class YieldEnvironment {
     let count: number = 1
     for (let seriesId of seriesIds) {
       const maturity = timestamp + THREE_MONTHS * count++
-      await wand.addSeries(seriesId, baseId, maturity, ilkIds, seriesId, seriesId)
+      await wand.addSeries(seriesId, baseId, maturity, assetIds, seriesId, seriesId)
       const fyToken = (await ethers.getContractAt(
         'FYToken',
         (await cauldron.series(seriesId)).fyToken,
@@ -401,7 +406,8 @@ export class YieldEnvironment {
     // For each series and ilk we create a vault - vaults[seriesId][ilkId] = vaultId
     for (let seriesId of seriesIds) {
       const seriesVaults: Map<string, string> = new Map()
-      for (let ilkId of ilkIds) {
+      for (let ilkId of assetIds) {
+        // Including a vault whose ilk equals its base
         await ladle.build(seriesId, ilkId)
         seriesVaults.set(ilkId, await getLastVaultId(cauldron))
       }