encode refundETH on swaps with very high slippage with ETH input token. (Uniswap#28)

* add option to refundETH when encoding a swap

* Fix code style issues with Prettier

* add refundETH for high slippage ETH trades

* Fix code style issues with Prettier

* mismatched paren

* unit test

* address PR comments

Co-authored-by: Lint Action <[email protected]>

Author: ewilz

src/swapRouter.test.ts

@@ -27,7 +27,7 @@ describe('SwapRouter', () => {
   const liquidity = 1_000_000
 
   // v3
-  const makePool = (token0: Token, token1: Token) => {
+  const makePool = (token0: Token, token1: Token, liquidity: number) => {
     return new Pool(token0, token1, feeAmount, sqrtRatioX96, liquidity, TickMath.getTickAtSqrtRatio(sqrtRatioX96), [
       {
         index: nearestUsableTick(TickMath.MIN_TICK, TICK_SPACINGS[feeAmount]),
@@ -50,10 +50,10 @@ describe('SwapRouter', () => {
     return new Pair(amount0, amount1)
   }
 
-  const pool_0_1 = makePool(token0, token1)
+  const pool_0_1 = makePool(token0, token1, liquidity)
   const pair_0_1 = makePair(token0, token1, liquidity)
 
-  const pool_1_WETH = makePool(token1, WETH)
+  const pool_1_WETH = makePool(token1, WETH, liquidity)
   const pair_1_WETH = makePair(token1, WETH, liquidity)
 
   const slippageTolerance = new Percent(1, 100)
@@ -465,6 +465,60 @@ describe('SwapRouter', () => {
           })
         })
       })
+
+      describe('high price impact with ETH input to result in refundETH being appended to calldata', () => {
+        const expectedCalldata =
+          '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'
+        const amountIn = CurrencyAmount.fromRawAmount(ETHER, JSBI.BigInt(100))
+        const pool_1_WETH_slippage = makePool(token1, WETH, 100)
+        const REFUND_ETH_FUNCTION_SIG = /12210e8a/
+
+        const v2Trade = V2Trade.exactIn(new V2Route([pair_1_WETH], ETHER, token1), amountIn)
+        const v3Trade = V3Trade.fromRoute(
+          new V3Route([pool_1_WETH_slippage], ETHER, token1),
+          amountIn,
+          TradeType.EXACT_INPUT
+        )
+
+        it('array of trades', async () => {
+          const trades = [v2Trade, await v3Trade]
+          const { calldata, value } = SwapRouter.swapCallParameters(trades, {
+            slippageTolerance,
+            recipient,
+            deadlineOrPreviousBlockhash: deadline,
+          })
+          expect(calldata).toEqual(expectedCalldata)
+          expect(calldata).toMatch(REFUND_ETH_FUNCTION_SIG)
+          expect(value).toBe('0xc8')
+        })
+      })
+
+      describe('high price impact with ERCO20 input does not result in refundETH call', () => {
+        const expectedCalldata =
+          '0x5ae401dc000000000000000000000000000000000000000000000000000000000000007b000000000000000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000040000000000000000000000000000000000000000000000000000000000000016000000000000000000000000000000000000000000000000000000000000000e4472b43f3000000000000000000000000000000000000000000000000000000000000006400000000000000000000000000000000000000000000000000000000000000620000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc20000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000e404e45aaf0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc20000000000000000000000000000000000000000000000000000000000000bb8000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000000000000000000000000000000000640000000000000000000000000000000000000000000000000000000000000030000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'
+        const amountIn = CurrencyAmount.fromRawAmount(token1, JSBI.BigInt(100))
+        const pool_1_WETH_slippage = makePool(token1, WETH, 100)
+        const REFUND_ETH_FUNCTION_SIG = /12210e8a/
+
+        const v2Trade = V2Trade.exactIn(new V2Route([pair_1_WETH], token1, WETH), amountIn)
+        const v3Trade = V3Trade.fromRoute(
+          new V3Route([pool_1_WETH_slippage], token1, WETH),
+          amountIn,
+          TradeType.EXACT_INPUT
+        )
+
+        it('array of trades', async () => {
+          const trades = [v2Trade, await v3Trade]
+          const { calldata, value } = SwapRouter.swapCallParameters(trades, {
+            slippageTolerance,
+            recipient,
+            deadlineOrPreviousBlockhash: deadline,
+          })
+          expect(calldata).toEqual(expectedCalldata)
+          expect(calldata).not.toMatch(REFUND_ETH_FUNCTION_SIG)
+          expect(value).toBe('0x00')
+        })
+      })
     })
 
     describe('ETH output', () => {
@@ -710,7 +764,7 @@ describe('SwapRouter', () => {
         const expectedCalldata =
           '0xac9650d80000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000700000000000000000000000000000000000000000000000000000000000000e0000000000000000000000000000000000000000000000000000000000000022000000000000000000000000000000000000000000000000000000000000003800000000000000000000000000000000000000000000000000000000000000400000000000000000000000000000000000000000000000000000000000000048000000000000000000000000000000000000000000000000000000000000005c000000000000000000000000000000000000000000000000000000000000006400000000000000000000000000000000000000000000000000000000000000104472b43f30000000000000000000000000000000000000000000000000000000000000064000000000000000000000000000000000000000000000000000000000000006100000000000000000000000000000000000000000000000000000000000000800000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000124b858183f0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000064000000000000000000000000000000000000000000000000000000000000005f00000000000000000000000000000000000000000000000000000000000000420000000000000000000000000000000000000001000bb80000000000000000000000000000000000000002000bb8c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044f2d5d56b000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2000000000000000000000000000000000000000000000000000000000032c7eb000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044f2d5d56b0000000000000000000000000000000000000000000000000000000000000001000000000000000000000000000000000000000000000000000000000032c8ad00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000010411ed56c90000000000000000000000000000000000000000000000000000000000000001000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc20000000000000000000000000000000000000000000000000000000000000bb8ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffc4000000000000000000000000000000000000000000000000000000000000003c000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000006000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044e90a182f00000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044e90a182f000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'
 
-        const pool_0_WETH = makePool(token0, WETH)
+        const pool_0_WETH = makePool(token0, WETH, liquidity)
         const amountIn = CurrencyAmount.fromRawAmount(token0, JSBI.BigInt(100))
         const v2Trade = V2Trade.exactIn(new V2Route([pair_0_1, pair_1_WETH], token0, WETH), amountIn)
         const v3Trade = V3Trade.fromRoute(
@@ -907,6 +961,7 @@ describe('SwapRouter', () => {
       describe('when input is native', () => {
         const expectedCalldata =
           '0xac9650d8000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000080000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000022000000000000000000000000000000000000000000000000000000000000002a00000000000000000000000000000000000000000000000000000000000000300000000000000000000000000000000000000000000000000000000000000036000000000000000000000000000000000000000000000000000000000000003c000000000000000000000000000000000000000000000000000000000000004a0000000000000000000000000000000000000000000000000000000000000050000000000000000000000000000000000000000000000000000000000000000e404e45aaf000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc200000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000bb80000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000a00000000000000000000000000000000000000000000000000000000000000070000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044f2d5d56b0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000032c8a50000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000241c58db4f000000000000000000000000000000000000000000000000000000000032c8ad000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000024571ac8b0000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000024571ac8b000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000a4f100b2050000000000000000000000000000000000000000000000000000000000000002000000000000000000000000c02aaa39b223fe8d0a0e5c4f27ead9083c756cc2000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000024496169970000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044e90a182f0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000'
+
         const ETH = Ether.onChain(1)
         const amountIn = CurrencyAmount.fromRawAmount(ETH, JSBI.BigInt(10))
         const v3Trade = V3Trade.fromRoute(new V3Route([pool_1_WETH], ETH, token1), amountIn, TradeType.EXACT_INPUT)

src/swapRouter.ts

@@ -24,6 +24,7 @@ import { MulticallExtended, Validation } from './multicallExtended'
 import { PaymentsExtended } from './paymentsExtended'
 
 const ZERO = JSBI.BigInt(0)
+const REFUND_ETH_PRICE_IMPACT_THRESHOLD = new Percent(JSBI.BigInt(50), JSBI.BigInt(100))
 
 /**
  * Options for producing the arguments to send calls to the router.
@@ -62,6 +63,12 @@ export interface SwapAndAddOptions extends SwapOptions {
   outputTokenPermit?: PermitOptions
 }
 
+type AnyTradeType =
+  | Trade<Currency, Currency, TradeType>
+  | V2Trade<Currency, Currency, TradeType>
+  | V3Trade<Currency, Currency, TradeType>
+  | (V2Trade<Currency, Currency, TradeType> | V3Trade<Currency, Currency, TradeType>)[]
+
 /**
  * Represents the Uniswap V2 + V3 SwapRouter02, and has static methods for helping execute trades.
  */
@@ -176,11 +183,7 @@ export abstract class SwapRouter {
   }
 
   private static encodeSwaps(
-    trades:
-      | Trade<Currency, Currency, TradeType>
-      | V2Trade<Currency, Currency, TradeType>
-      | V3Trade<Currency, Currency, TradeType>
-      | (V2Trade<Currency, Currency, TradeType> | V3Trade<Currency, Currency, TradeType>)[],
+    trades: AnyTradeType,
     options: SwapOptions,
     isSwapAndAdd?: boolean
   ): {
@@ -357,8 +360,9 @@ export abstract class SwapRouter {
       }
     }
 
-    // must refund when paying in ETH, but with an uncertain input amount
-    if (inputIsNative && sampleTrade.tradeType === TradeType.EXACT_OUTPUT) {
+    // must refund when paying in ETH: either with an uncertain input amount OR if there's a chance of a partial fill.
+    // unlike ERC20's, the full ETH value must be sent in the transaction, so the rest must be refunded.
+    if (inputIsNative && (sampleTrade.tradeType === TradeType.EXACT_OUTPUT || SwapRouter.riskOfPartialFill(trades))) {
       calldatas.push(Payments.encodeRefundETH())
     }
 
@@ -374,11 +378,7 @@ export abstract class SwapRouter {
    * @param options options for the call parameters
    */
   public static swapAndAddCallParameters(
-    trades:
-      | Trade<Currency, Currency, TradeType>
-      | V2Trade<Currency, Currency, TradeType>
-      | V3Trade<Currency, Currency, TradeType>
-      | (V2Trade<Currency, Currency, TradeType> | V3Trade<Currency, Currency, TradeType>)[],
+    trades: AnyTradeType,
     options: SwapAndAddOptions,
     position: Position,
     addLiquidityOptions: CondensedAddLiquidityOptions,
@@ -469,6 +469,26 @@ export abstract class SwapRouter {
     }
   }
 
+  // if price impact is very high, there's a chance of hitting max/min prices resulting in a partial fill of the swap
+  private static riskOfPartialFill(trades: AnyTradeType): boolean {
+    if (Array.isArray(trades)) {
+      return trades.some((trade) => {
+        return SwapRouter.v3TradeWithHighPriceImpact(trade)
+      })
+    } else {
+      return SwapRouter.v3TradeWithHighPriceImpact(trades)
+    }
+  }
+
+  private static v3TradeWithHighPriceImpact(
+    trade:
+      | Trade<Currency, Currency, TradeType>
+      | V2Trade<Currency, Currency, TradeType>
+      | V3Trade<Currency, Currency, TradeType>
+  ): boolean {
+    return !(trade instanceof V2Trade) && trade.priceImpact.greaterThan(REFUND_ETH_PRICE_IMPACT_THRESHOLD)
+  }
+
   private static getPositionAmounts(
     position: Position,
     zeroForOne: boolean