Make the #bestTradeExactIn and #bestTradeExactOut more strict about input pairs

src/entities/trade.ts

@@ -112,10 +112,7 @@ export class Trade {
     originalAmountIn: TokenAmount = amountIn,
     bestTrades: Trade[] = []
   ): Trade[] {
-    if (pairs.length === 0) {
-      return bestTrades
-    }
-
+    invariant(pairs.length > 0, 'PAIRS')
     invariant(maxHops > 0, 'MAX_HOPS')
     invariant(originalAmountIn === amountIn || currentPairs.length > 0, 'INVALID_RECURSION')
 
@@ -145,7 +142,7 @@ export class Trade {
           maxNumResults,
           inputOutputComparator
         )
-      } else if (maxHops > 1) {
+      } else if (maxHops > 1 && pairs.length > 1) {
         const pairsExcludingThisPair = pairs.slice(0, i).concat(pairs.slice(i + 1, pairs.length))
 
         // otherwise, consider all the other paths that lead from this token as long as we have not exceeded maxHops
@@ -182,10 +179,7 @@ export class Trade {
     originalAmountOut: TokenAmount = amountOut,
     bestTrades: Trade[] = []
   ): Trade[] {
-    if (pairs.length === 0) {
-      return bestTrades
-    }
-
+    invariant(pairs.length > 0, 'PAIRS')
     invariant(maxHops > 0, 'MAX_HOPS')
     invariant(originalAmountOut === amountOut || currentPairs.length > 0, 'INVALID_RECURSION')
 
@@ -212,7 +206,7 @@ export class Trade {
           maxNumResults,
           inputOutputComparator
         )
-      } else if (maxHops > 1) {
+      } else if (maxHops > 1 && pairs.length > 1) {
         const pairsExcludingThisPair = pairs.slice(0, i).concat(pairs.slice(i + 1, pairs.length))
 
         // otherwise, consider all the other paths that arrive at this token as long as we have not exceeded maxHops

test/trade.test.ts

@@ -14,6 +14,15 @@ describe('Trade', () => {
   const pair_1_3 = new Pair(new TokenAmount(token1, JSBI.BigInt(1200)), new TokenAmount(token3, JSBI.BigInt(1300)))
 
   describe('#bestTradeExactIn', () => {
+    it('throws with empty pairs', () => {
+      expect(() => Trade.bestTradeExactIn([], new TokenAmount(token0, JSBI.BigInt(100)), token2)).toThrow('PAIRS')
+    })
+    it('throws with max hops of 0', () => {
+      expect(() =>
+        Trade.bestTradeExactIn([pair_0_2], new TokenAmount(token0, JSBI.BigInt(100)), token2, { maxHops: 0 })
+      ).toThrow('MAX_HOPS')
+    })
+
     it('provides best route', () => {
       const result = Trade.bestTradeExactIn(
         [pair_0_1, pair_0_2, pair_1_2],
@@ -77,6 +86,15 @@ describe('Trade', () => {
   })
 
   describe('#bestTradeExactOut', () => {
+    it('throws with empty pairs', () => {
+      expect(() => Trade.bestTradeExactOut([], token0, new TokenAmount(token2, JSBI.BigInt(100)))).toThrow('PAIRS')
+    })
+    it('throws with max hops of 0', () => {
+      expect(() =>
+        Trade.bestTradeExactOut([pair_0_2], token0, new TokenAmount(token2, JSBI.BigInt(100)), { maxHops: 0 })
+      ).toThrow('MAX_HOPS')
+    })
+
     it('provides best route', () => {
       const result = Trade.bestTradeExactOut(
         [pair_0_1, pair_0_2, pair_1_2],