add some txscript support for parsing taproot scripts

txscript/pkscript.go

@@ -239,26 +239,11 @@ func computeNonWitnessPkScript(sigScript []byte) (PkScript, error) {
 
 // computeWitnessPkScript computes the script of an output by looking at the
 // spending input's witness.
-// IMPORTANT: With the addition of taproot, we can no longer say for certain
-// what kind of script the witness is in most cases. The only case in which we
-// can say for sure is when the witness data has an annex as the last push. In
-// that case, we can identify the script type, but we lack the ability to
-// reconstruct the script itself.
+// IMPORTANT: With the addition of taproot, we can not say for certain
+// what kind of script the witness is.
 func computeWitnessPkScript(witness wire.TxWitness) (PkScript, error) {
 	var pkScript PkScript
-	switch {
-	// If the last push starts with the annex flag, this is a taproot spend.
-	// We can set the script class, but we can't say what the pubkey script
-	// looks like with just the witness data.
-	case isAnnexedWitness(witness):
-		pkScript.class = WitnessV1TaprootTy
-
-	// For any other witnesses, we can't say for certain what type it is or what
-	// the pubkey script will be.
-	default:
-		pkScript.class = WitnessUnknownTy
-	}
-
+	pkScript.class = WitnessUnknownTy
 	return pkScript, nil
 }
 

txscript/standard.go

@@ -1007,6 +1007,15 @@ func ExtractPkScriptAddrs(pkScript []byte, chainParams *chaincfg.Params) (Script
 		return WitnessV0ScriptHashTy, addrs, 1, nil
 	}
 
+	if hash := extractWitnessV1ScriptHash(pkScript); hash != nil {
+		var addrs []btcutil.Address
+		addr, err := btcutil.NewAddressTaproot(hash, chainParams)
+		if err == nil {
+			addrs = append(addrs, addr)
+		}
+		return WitnessV1TaprootTy, addrs, 1, nil
+	}
+
 	// case WitnessV1TaprootTy:
 	// 	requiredSigs = 1
 	// 	addr, err := btcutil.NewAddressTaproot(pops[1].data,

txscript/standard_test.go

@@ -71,6 +71,20 @@ func newAddressScriptHash(scriptHash []byte) btcutil.Address {
 	return addr
 }
 
+// newAddressTaproot returns a new btcutil.AddressTaproot from the
+// provided hash.  It panics if an error occurs.  This is only used in the tests
+// as a helper since the only way it can fail is if there is an error in the
+// test source code.
+func newAddressTaproot(scriptHash []byte) btcutil.Address {
+	addr, err := btcutil.NewAddressTaproot(scriptHash,
+		&chaincfg.MainNetParams)
+	if err != nil {
+		panic("invalid script hash in test source")
+	}
+
+	return addr
+}
+
 // TestExtractPkScriptAddrs ensures that extracting the type, addresses, and
 // number of required signatures from PkScripts works as intended.
 func TestExtractPkScriptAddrs(t *testing.T) {
@@ -311,8 +325,15 @@ func TestExtractPkScriptAddrs(t *testing.T) {
 			reqSigs: 1,
 			class:   MultiSigTy,
 		},
-		// from real tx: 691dd277dc0e90a462a3d652a1171686de49cf19067cd33c7df0392833fb986a, vout 44
-		// invalid public keys
+		{
+			name: "v1 p2tr witness-script-hash",
+			script: hexToBytes("51201a82f7457a9ba6ab1074e9f50" +
+				"053eefc637f8b046e389b636766bdc7d1f676f8"),
+			addrs: []btcutil.Address{newAddressTaproot(
+				hexToBytes("1a82f7457a9ba6ab1074e9f50053eefc637f8b046e389b636766bdc7d1f676f8"))},
+			reqSigs: 1,
+			class:   WitnessV1TaprootTy,
+		},
 		{
 			name: "1 of 3 multisig with invalid pubkeys 2",
 			script: hexToBytes("514134633365633235396337346461636" +