routing/payment_session: remove prebuilt payment session

Since we no longer use payment sessions for send to route, we remove the
prebuilt one.

routing/payment_lifecycle.go

@@ -391,7 +391,7 @@ func errorToPaymentFailure(err error) channeldb.FailureReason {
 		errNoTlvPayload,
 		errNoPaymentAddr,
 		errNoPathFound,
-		errPrebuiltRouteTried:
+		errEmptyPaySession:
 
 		return channeldb.FailureReasonNoRoute
 

routing/payment_session.go

@@ -13,9 +13,9 @@ import (
 const BlockPadding uint16 = 3
 
 var (
-	// errPrebuiltRouteTried is returned when the single pre-built route
-	// failed and there is nothing more we can do.
-	errPrebuiltRouteTried = errors.New("pre-built route already tried")
+	// errEmptyPaySession is returned when the empty payment session is
+	// queried for a route.
+	errEmptyPaySession = errors.New("empty payment session")
 )
 
 // PaymentSession is used during SendPayment attempts to provide routes to
@@ -50,8 +50,7 @@ type paymentSession struct {
 
 	payment *LightningPayment
 
-	preBuiltRoute      *route.Route
-	preBuiltRouteTried bool
+	empty bool
 
 	pathFinder pathFinder
 }
@@ -68,18 +67,8 @@ type paymentSession struct {
 func (p *paymentSession) RequestRoute(maxAmt, feeLimit lnwire.MilliSatoshi,
 	activeShards, height uint32) (*route.Route, error) {
 
-	switch {
-
-	// If we have a pre-built route, use that directly.
-	case p.preBuiltRoute != nil && !p.preBuiltRouteTried:
-		p.preBuiltRouteTried = true
-
-		return p.preBuiltRoute, nil
-
-	// If the pre-built route has been tried already, the payment session is
-	// over.
-	case p.preBuiltRoute != nil:
-		return nil, errPrebuiltRouteTried
+	if p.empty {
+		return nil, errEmptyPaySession
 	}
 
 	// Add BlockPadding to the finalCltvDelta so that the receiving node

routing/payment_session_source.go

@@ -75,23 +75,13 @@ func (m *SessionSource) NewPaymentSession(p *LightningPayment) (
 	}, nil
 }
 
-// NewPaymentSessionForRoute creates a new paymentSession instance that is just
-// used for failure reporting to missioncontrol.
-func (m *SessionSource) NewPaymentSessionForRoute(preBuiltRoute *route.Route) PaymentSession {
-	return &paymentSession{
-		sessionSource: m,
-		preBuiltRoute: preBuiltRoute,
-	}
-}
-
 // NewPaymentSessionEmpty creates a new paymentSession instance that is empty,
 // and will be exhausted immediately. Used for failure reporting to
 // missioncontrol for resumed payment we don't want to make more attempts for.
 func (m *SessionSource) NewPaymentSessionEmpty() PaymentSession {
 	return &paymentSession{
 		sessionSource: m,
-		preBuiltRoute:      &route.Route{},
-		preBuiltRouteTried: true,
+		empty:         true,
 	}
 }
 

routing/router.go

@@ -161,11 +161,6 @@ type PaymentSessionSource interface {
 	// finding a path to the payment's destination.
 	NewPaymentSession(p *LightningPayment) (PaymentSession, error)
 
-	// NewPaymentSessionForRoute creates a new paymentSession instance that
-	// is just used for failure reporting to missioncontrol, and will only
-	// attempt the given route.
-	NewPaymentSessionForRoute(preBuiltRoute *route.Route) PaymentSession
-
 	// NewPaymentSessionEmpty creates a new paymentSession instance that is
 	// empty, and will be exhausted immediately. Used for failure reporting
 	// to missioncontrol for resumed payment we don't want to make more