itest: fixes for custom channels NoOp HTLCs

We add a new litd argument that triggers the usage of NoOp HTLCs. We may
not use that argument in itests where backwards compatibility is
enabled, as currently this leads to a channel force-closure.

Author: GeorgeTsagk

itest/litd_custom_channels_test.go

@@ -105,6 +105,10 @@ var (
 			"8820600",
 		"--taproot-assets.experimental.rfq.acceptpricedeviationppm=50000",
 	}...)
+
+	litdArgNoopHTLCs = []string{
+		"--taproot-assets.channel.noop-htlcs",
+	}
 )
 
 const (
@@ -1182,6 +1186,8 @@ func testCustomChannelsGroupTranchesForceClose(ctx context.Context,
 	lndArgs := slices.Clone(lndArgsTemplate)
 	litdArgs := slices.Clone(litdArgsTemplate)
 
+	litdArgs = append(litdArgs, litdArgNoopHTLCs...)
+
 	// We use Charlie as the proof courier. But in order for Charlie to also
 	// use itself, we need to define its port upfront.
 	charliePort := port.NextAvailablePort()
@@ -1289,16 +1295,23 @@ func testCustomChannelsGroupTranchesForceClose(ctx context.Context,
 	// that transports assets from two tranches.
 	// ------------
 	const (
-		keySendAmount  = 5000
-		numSends       = 6
-		totalFirstSend = keySendAmount * numSends
+		keySendAmount    = 5000
+		keySendSatAmount = 5000
+		numSends         = 6
+		totalFirstSend   = keySendAmount * numSends
 	)
 	for i := 0; i < numSends; i++ {
 		sendAssetKeySendPayment(
 			t.t, charlie, dave, keySendAmount, nil,
 			fn.None[int64](), withGroupKey(groupKey),
 		)
 	}
+
+	// With noop HTLCs implemented the sats balance of Dave will only
+	// increase up to the reserve amount. Let's make a direct non-asset
+	// keysend to make sure the sats balance is also enough.
+	sendKeySendPayment(t.t, charlie, dave, keySendSatAmount)
+
 	logBalanceGroup(t.t, nodes, groupIDs, "after keysend Charlie->Dave")
 
 	// ------------
@@ -1538,8 +1551,9 @@ func testCustomChannelsGroupTranchesHtlcForceClose(ctx context.Context,
 	// First, we'll send over some funds from Charlie to Dave, as we want
 	// Dave to be able to extend HTLCs in the other direction.
 	const (
-		numPayments   = 10
-		keySendAmount = 2_500
+		numPayments      = 10
+		keySendAmount    = 2_500
+		keySendSatAmount = 5000
 	)
 	for i := 0; i < numPayments; i++ {
 		sendAssetKeySendPayment(
@@ -1548,6 +1562,11 @@ func testCustomChannelsGroupTranchesHtlcForceClose(ctx context.Context,
 		)
 	}
 
+	// With noop HTLCs implemented the sats balance of Dave will only
+	// increase up to the reserve amount. Let's make a direct non-asset
+	// keysend to make sure the sats balance is also enough.
+	sendKeySendPayment(t.t, charlie, dave, keySendSatAmount)
+
 	// Now that both parties have some funds, we'll move onto the main test.
 	//
 	// We'll make 2 hodl invoice for each peer, so 4 total. From Charlie's
@@ -2079,6 +2098,8 @@ func testCustomChannelsBreach(ctx context.Context, net *NetworkHarness,
 		fmt.Sprintf(node.ListenerFormat, charliePort),
 	))
 
+	litdArgs = append(litdArgs, litdArgNoopHTLCs...)
+
 	// Charlie will be the breached party. We set --nolisten to ensure Dave
 	// won't be able to connect to him and trigger the channel protection
 	// logic automatically. We also can't have Charlie automatically
@@ -2295,6 +2316,8 @@ func testCustomChannelsLiquidityEdgeCasesCore(ctx context.Context,
 		fmt.Sprintf(node.ListenerFormat, charliePort),
 	))
 
+	litdArgs = append(litdArgs, litdArgNoopHTLCs...)
+
 	// The topology we are going for looks like the following:
 	//
 	// Charlie  --[assets]-->  Dave  --[sats]-->  Erin  --[assets]-->  Fabia
@@ -3227,6 +3250,8 @@ func testCustomChannelsStrictForwarding(ctx context.Context,
 		fmt.Sprintf(node.ListenerFormat, charliePort),
 	))
 
+	litdArgs = append(litdArgs, litdArgNoopHTLCs...)
+
 	// The topology we are going for looks like the following:
 	//
 	// Charlie  --[assets]-->  Dave  --[sats]-->  Erin  --[assets]-->  Fabia
@@ -4139,6 +4164,8 @@ func runCustomChannelsHtlcForceClose(ctx context.Context, t *harnessTest,
 	lndArgs := slices.Clone(lndArgsTemplate)
 	litdArgs := slices.Clone(litdArgsTemplate)
 
+	litdArgs = append(litdArgs, litdArgNoopHTLCs...)
+
 	// Zane will serve as our designated Universe node.
 	zane, err := net.NewNode(
 		t.t, "Zane", lndArgs, false, true, litdArgs...,
@@ -4219,16 +4246,24 @@ func runCustomChannelsHtlcForceClose(ctx context.Context, t *harnessTest,
 	// First, we'll send over some funds from Alice to Bob, as we want Bob
 	// to be able to extend HTLCs in the other direction.
 	const (
-		numPayments   = 10
-		keySendAmount = 2_500
+		numPayments        = 10
+		keySendAssetAmount = 2_500
+		keySendSatAmount   = 5_000
 	)
 	for i := 0; i < numPayments; i++ {
 		sendAssetKeySendPayment(
-			t.t, alice, bob, keySendAmount, assetID,
+			t.t, alice, bob, keySendAssetAmount, assetID,
 			fn.None[int64](),
 		)
 	}
 
+	// With noop HTLCs implemented the sats balance of Bob will only
+	// increase up to the reserve amount. Let's make a direct non-asset
+	// keysend to make sure the sats balance is also enough.
+	sendKeySendPayment(t.t, alice, bob, keySendSatAmount)
+
+	logBalance(t.t, nodes, assetID, "after keysends to Bob")
+
 	// Now that both parties have some funds, we'll move onto the main test.
 	//
 	// We'll make 2 hodl invoice for each peer, so 4 total. From Alice's
@@ -4717,6 +4752,8 @@ func testCustomChannelsSelfPayment(ctx context.Context, net *NetworkHarness,
 		fmt.Sprintf(node.ListenerFormat, alicePort),
 	))
 
+	litdArgs = append(litdArgs, litdArgNoopHTLCs...)
+
 	// Next, we'll make Alice and Bob, who will be the main nodes under
 	// test.
 	alice, err := net.NewNodeWithPort(