itest: add itest for p2tr via ComputeInputScript

lntest/itest/lnd_remote_signer_test.go

@@ -127,6 +127,9 @@ func testRemoteSigner(net *lntest.NetworkHarness, t *harnessTest) {
 			defer cancel()
 
 			testTaprootSendCoinsKeySpendBip86(ctxt, tt, wo, net)
+			testTaprootComputeInputScriptKeySpendBip86(
+				ctxt, tt, wo, net,
+			)
 			testTaprootSignOutputRawScriptSpend(ctxt, tt, wo, net)
 			testTaprootSignOutputRawKeySpendBip86(ctxt, tt, wo, net)
 			testTaprootSignOutputRawKeySpendRootHash(

lntest/itest/lnd_taproot_test.go

@@ -47,6 +47,7 @@ func testTaproot(net *lntest.NetworkHarness, t *harnessTest) {
 	defer cancel()
 
 	testTaprootSendCoinsKeySpendBip86(ctxt, t, net.Alice, net)
+	testTaprootComputeInputScriptKeySpendBip86(ctxt, t, net.Alice, net)
 	testTaprootSignOutputRawScriptSpend(ctxt, t, net.Alice, net)
 	testTaprootSignOutputRawKeySpendBip86(ctxt, t, net.Alice, net)
 	testTaprootSignOutputRawKeySpendRootHash(ctxt, t, net.Alice, net)
@@ -117,6 +118,108 @@ func testTaprootSendCoinsKeySpendBip86(ctxt context.Context,
 	confirmAddress(ctxt, t, net, alice, p2trResp.Address)
 }
 
+// testTaprootComputeInputScriptKeySpendBip86 tests sending to and spending
+// from p2tr key spend only (BIP-0086) addresses through the ComputeInputScript
+// RPC.
+func testTaprootComputeInputScriptKeySpendBip86(ctxt context.Context,
+	t *harnessTest, alice *lntest.HarnessNode, net *lntest.NetworkHarness) {
+
+	// We'll start the test by sending Alice some coins, which she'll use to
+	// send to herself on a p2tr output.
+	net.SendCoins(t.t, btcutil.SatoshiPerBitcoin, alice)
+
+	// Let's create a p2tr address now.
+	p2trAddr, p2trPkScript := newAddrWithScript(
+		ctxt, t.t, alice, lnrpc.AddressType_TAPROOT_PUBKEY,
+	)
+
+	// Send the coins from Alice's wallet to her own, but to the new p2tr
+	// address.
+	_, err := alice.SendCoins(ctxt, &lnrpc.SendCoinsRequest{
+		Addr:   p2trAddr.String(),
+		Amount: testAmount,
+	})
+	require.NoError(t.t, err)
+
+	txid, err := waitForTxInMempool(net.Miner.Client, defaultTimeout)
+	require.NoError(t.t, err)
+
+	// Wait until bob has seen the tx and considers it as owned.
+	p2trOutputIndex := getOutputIndex(t, net.Miner, txid, p2trAddr.String())
+	op := &lnrpc.OutPoint{
+		TxidBytes:   txid[:],
+		OutputIndex: uint32(p2trOutputIndex),
+	}
+	assertWalletUnspent(t, alice, op)
+
+	p2trOutpoint := wire.OutPoint{
+		Hash:  *txid,
+		Index: uint32(p2trOutputIndex),
+	}
+
+	// Mine a block to clean up the mempool.
+	mineBlocks(t, net, 1, 1)
+
+	// We'll send the coins back to a p2wkh address.
+	p2wkhAddr, p2wkhPkScript := newAddrWithScript(
+		ctxt, t.t, alice, lnrpc.AddressType_WITNESS_PUBKEY_HASH,
+	)
+
+	// Create fee estimation for a p2tr input and p2wkh output.
+	feeRate := chainfee.SatPerKWeight(12500)
+	estimator := input.TxWeightEstimator{}
+	estimator.AddTaprootKeySpendInput(txscript.SigHashDefault)
+	estimator.AddP2WKHOutput()
+	estimatedWeight := int64(estimator.Weight())
+	requiredFee := feeRate.FeeForWeight(estimatedWeight)
+
+	tx := wire.NewMsgTx(2)
+	tx.TxIn = []*wire.TxIn{{
+		PreviousOutPoint: p2trOutpoint,
+	}}
+	value := int64(testAmount - requiredFee)
+	tx.TxOut = []*wire.TxOut{{
+		PkScript: p2wkhPkScript,
+		Value:    value,
+	}}
+
+	var buf bytes.Buffer
+	require.NoError(t.t, tx.Serialize(&buf))
+
+	utxoInfo := []*signrpc.TxOut{{
+		PkScript: p2trPkScript,
+		Value:    testAmount,
+	}}
+	signResp, err := alice.SignerClient.ComputeInputScript(
+		ctxt, &signrpc.SignReq{
+			RawTxBytes: buf.Bytes(),
+			SignDescs: []*signrpc.SignDescriptor{{
+				Output:     utxoInfo[0],
+				InputIndex: 0,
+				Sighash:    uint32(txscript.SigHashDefault),
+			}},
+			PrevOutputs: utxoInfo,
+		},
+	)
+	require.NoError(t.t, err)
+
+	tx.TxIn[0].Witness = signResp.InputScripts[0].Witness
+
+	// Serialize, weigh and publish the TX now, then make sure the
+	// coins are sent and confirmed to the final sweep destination address.
+	publishTxAndConfirmSweep(
+		ctxt, t, net, alice, tx, estimatedWeight,
+		&chainrpc.SpendRequest{
+			Outpoint: &chainrpc.Outpoint{
+				Hash:  p2trOutpoint.Hash[:],
+				Index: p2trOutpoint.Index,
+			},
+			Script: p2trPkScript,
+		},
+		p2wkhAddr.String(),
+	)
+}
+
 // testTaprootSignOutputRawScriptSpend tests sending to and spending from p2tr
 // script addresses using the script path with the SignOutputRaw RPC.
 func testTaprootSignOutputRawScriptSpend(ctxt context.Context, t *harnessTest,