Merge pull request #167 from onflow/lionel/fix-multiswapper-p1-p2

Fix MultiSwapper partial quoteIn tie-break

Author: nialexsan

cadence/contracts/connectors/SwapConnectors.cdc

@@ -183,7 +183,8 @@ access(all) contract SwapConnectors {
                 } else if !hasFull {
                     // partial coverage group (only when no full route found)
                     // in this case, prefer maximum outAmount 
-                    if quote.outAmount > bestOutAmount {
+                    if quote.outAmount > bestOutAmount
+                        || (quote.outAmount == bestOutAmount && quote.inAmount < bestInAmount) {
                         bestIdx = i
                         bestInAmount = quote.inAmount
                         bestOutAmount = quote.outAmount

cadence/tests/SwapConnectorsMultiSwapper_test.cdc

@@ -190,6 +190,29 @@ fun testQuoteOutCapLimitsRoute() {
     Test.assertEqual(5.0, quote.outAmount) // 10.0 * 0.5
 }
 
+/// quoteIn — when two partial routes tie on outAmount, the one with the lower
+/// inAmount should win.
+///
+access(all)
+fun testQuoteInPartialTieBreaksOnLowerInAmount() {
+    let forDesired = 10.0
+    let configs = [
+        makeConfig(priceRatio: 0.5, maxOut: 5.0),
+        makeConfig(priceRatio: 1.0, maxOut: 5.0)
+    ]
+
+    let result = executeScript(
+        "./scripts/multi-swapper/mock_quote_in.cdc",
+        [testTokenAccount.address, configs, inVaultType, outVaultType, forDesired, false]
+    )
+    Test.expect(result, Test.beSucceeded())
+    let quote = result.returnValue! as! SwapConnectors.MultiSwapperQuote
+
+    Test.assertEqual(1, quote.swapperIndex)
+    Test.assertEqual(5.0, quote.inAmount)
+    Test.assertEqual(5.0, quote.outAmount)
+}
+
 /// quoteOut — four swappers: maximize outAmount first, then minimize inAmount as tiebreaker.
 ///
 /// S0 (suboptimal):  priceRatio=1.0,  maxOut=100.0 → outAmount=100.0, inAmount=100.0