fix: cowswap buyAmountCryptoBaseUnit logic (#1230)

packages/swapper/src/swappers/cow/getCowSwapTradeQuote/getCowSwapTradeQuote.test.ts

@@ -176,7 +176,7 @@ const expectedTradeQuoteSmallAmountWethToFox: TradeQuote<KnownChainIds.EthereumM
     networkFeeCryptoBaseUnit: '0',
   },
   sellAmountBeforeFeesCryptoBaseUnit: '1000000000000',
-  buyAmountCryptoBaseUnit: '145018118182475950905', // 14501 FOX
+  buyAmountCryptoBaseUnit: '0', // 0 FOX
   sources: [{ name: SwapperName.CowSwap, proportion: '1' }],
   allowanceContract: '0xc92e8bdf79f0507f65a392b0ab4667716bfe0110',
   buyAsset: FOX,

packages/swapper/src/swappers/cow/getCowSwapTradeQuote/getCowSwapTradeQuote.ts

@@ -65,12 +65,13 @@ export async function getCowSwapTradeQuote(
     const { minimum, maximum } = await getCowSwapMinMax(deps, sellAsset, buyAsset)
 
     const minQuoteSellAmount = bnOrZero(minimum).times(bn(10).exponentiatedBy(sellAsset.precision))
+    const isSellAmountBelowMinimum = bnOrZero(sellAmountBeforeFeesCryptoBaseUnit).lt(
+      minQuoteSellAmount,
+    )
 
     // making sure we do not have decimals for cowswap api (can happen at least from minQuoteSellAmount)
-    const normalizedSellAmount = normalizeIntegerAmount(
-      bnOrZero(sellAmountBeforeFeesCryptoBaseUnit).lt(minQuoteSellAmount)
-        ? minQuoteSellAmount
-        : sellAmountBeforeFeesCryptoBaseUnit,
+    const normalizedSellAmountCryptoBaseUnit = normalizeIntegerAmount(
+      isSellAmountBelowMinimum ? minQuoteSellAmount : sellAmountBeforeFeesCryptoBaseUnit,
     )
 
     const apiInput: CowSwapSellQuoteApiInput = {
@@ -82,7 +83,7 @@ export async function getCowSwapTradeQuote(
       partiallyFillable: false,
       from: DEFAULT_ADDRESS,
       kind: ORDER_KIND_SELL,
-      sellAmountBeforeFee: normalizedSellAmount,
+      sellAmountBeforeFee: normalizedSellAmountCryptoBaseUnit,
     }
 
     /**
@@ -142,11 +143,18 @@ export async function getCowSwapTradeQuote(
 
     const feeData = feeDataOptions['fast']
 
-    // If original sellAmount is < minQuoteSellAmount, we don't want to replace it with normalizedSellAmount
+    const isQuoteSellAmountBelowMinimum = bnOrZero(sellAmountCryptoBaseUnit).lt(minQuoteSellAmount)
+    // If isQuoteSellAmountBelowMinimum we don't want to replace it with normalizedSellAmount
     // The purpose of this was to get a quote from CowSwap even with small amounts
-    const quoteSellAmount = bnOrZero(sellAmountCryptoBaseUnit).lt(minQuoteSellAmount)
+    const quoteSellAmountCryptoBaseUnit = isQuoteSellAmountBelowMinimum
       ? sellAmountBeforeFeesCryptoBaseUnit
-      : normalizedSellAmount
+      : normalizedSellAmountCryptoBaseUnit
+
+    // Similarly, if isQuoteSellAmountBelowMinimum we can't use the buy amount from the quote
+    // because we aren't actually selling the minimum amount (we are attempting to sell an amount less than it)
+    const quoteBuyAmountCryptoBaseUnit = isQuoteSellAmountBelowMinimum
+      ? '0'
+      : buyAmountCryptoBaseUnit
 
     return {
       rate,
@@ -164,8 +172,8 @@ export async function getCowSwapTradeQuote(
         buyAssetTradeFeeUsd: '0', // Trade fees for buy Asset are always 0 since trade fees are subtracted from sell asset
         sellAssetTradeFeeUsd,
       },
-      sellAmountBeforeFeesCryptoBaseUnit: quoteSellAmount,
-      buyAmountCryptoBaseUnit,
+      sellAmountBeforeFeesCryptoBaseUnit: quoteSellAmountCryptoBaseUnit,
+      buyAmountCryptoBaseUnit: quoteBuyAmountCryptoBaseUnit,
       sources: DEFAULT_SOURCE,
       allowanceContract: COW_SWAP_VAULT_RELAYER_ADDRESS,
       buyAsset,