routing/pathfind: evaluate TLV support sooner

We move up the check for TLV support, since we will later use it to
determine if we can use dependent features, e.g. TLV records and payment
addresses.

routing/pathfind_test.go

@@ -1095,6 +1095,10 @@ func TestNewRoute(t *testing.T) {
 		// indicated by hops.
 		paymentAmount lnwire.MilliSatoshi
 
+		// destFeatures is a feature vector, that if non-nil, will
+		// overwrite the final hop's feature vector in the graph.
+		destFeatures *lnwire.FeatureVector
+
 		// expectedFees is a list of fees that every hop is expected
 		// to charge for forwarding.
 		expectedFees []lnwire.MilliSatoshi
@@ -1123,6 +1127,8 @@ func TestNewRoute(t *testing.T) {
 		// expectedErrorCode indicates the expected error code when
 		// expectError is true.
 		expectedErrorCode errorCode
+
+		expectedTLVPayload bool
 	}{
 		{
 			// For a single hop payment, no fees are expected to be paid.
@@ -1149,6 +1155,22 @@ func TestNewRoute(t *testing.T) {
 			expectedTimeLocks:     []uint32{1, 1},
 			expectedTotalAmount:   100130,
 			expectedTotalTimeLock: 6,
+		}, {
+			// For a two hop payment, only the fee for the first hop
+			// needs to be paid. The destination hop does not require
+			// a fee to receive the payment.
+			name:          "two hop tlv onion feature",
+			destFeatures:  tlvFeatures,
+			paymentAmount: 100000,
+			hops: []*channeldb.ChannelEdgePolicy{
+				createHop(0, 1000, 1000000, 10),
+				createHop(30, 1000, 1000000, 5),
+			},
+			expectedFees:          []lnwire.MilliSatoshi{130, 0},
+			expectedTimeLocks:     []uint32{1, 1},
+			expectedTotalAmount:   100130,
+			expectedTotalTimeLock: 6,
+			expectedTLVPayload:    true,
 		}, {
 			// A three hop payment where the first and second hop
 			// will both charge 1 msat. The fee for the first hop
@@ -1205,6 +1227,15 @@ func TestNewRoute(t *testing.T) {
 		}}
 
 	for _, testCase := range testCases {
+		testCase := testCase
+
+		// Overwrite the final hop's features if the test requires a
+		// custom feature vector.
+		if testCase.destFeatures != nil {
+			finalHop := testCase.hops[len(testCase.hops)-1]
+			finalHop.Node.Features = testCase.destFeatures
+		}
+
 		assertRoute := func(t *testing.T, route *route.Route) {
 			if route.TotalAmount != testCase.expectedTotalAmount {
 				t.Errorf("Expected total amount is be %v"+
@@ -1248,6 +1279,16 @@ func TestNewRoute(t *testing.T) {
 						route.Hops[i].OutgoingTimeLock)
 				}
 			}
+
+			finalHop := route.Hops[len(route.Hops)-1]
+			if !finalHop.LegacyPayload !=
+				testCase.expectedTLVPayload {
+
+				t.Errorf("Expected tlv payload: %t, "+
+					"but got: %t instead",
+					testCase.expectedTLVPayload,
+					!finalHop.LegacyPayload)
+			}
 		}
 
 		t.Run(testCase.name, func(t *testing.T) {