Don't use nullable script tree/script root parameters in Script.pay2tr()

Users had to cast null to ByteVector32?/ScriptTree? which was ugly. Now they
have to pass in either an explicit script/script root or use an explicit TaprootTweak.

Author: sstone

src/commonMain/kotlin/fr/acinq/bitcoin/Script.kt

@@ -480,19 +480,19 @@ public object Script {
 
     /**
      * @param internalKey internal public key that will be tweaked with the [scripts] provided.
-     * @param scripts optional spending scripts that can be used instead of key-path spending.
+     * @param scripts spending script tree.
      */
     @JvmStatic
-    public fun pay2tr(internalKey: XonlyPublicKey, scripts: ScriptTree?): List<ScriptElt> = pay2tr(internalKey, scripts?.hash())
+    public fun pay2tr(internalKey: XonlyPublicKey, scripts: ScriptTree): List<ScriptElt> =
+        pay2tr(internalKey, scripts.hash())
 
     /**
      * @param internalKey internal public key that will be tweaked with the [scriptsRoot] provided.
-     * @param scriptsRoot optional merkle root of the spending scripts that can be used instead of key-path spending.
+     * @param scriptsRoot merkle root of the spending script tree.
      */
     @JvmStatic
-    public fun pay2tr(internalKey: XonlyPublicKey, scriptsRoot: ByteVector32?): List<ScriptElt> {
-        val tweak = scriptsRoot?.let { Crypto.TaprootTweak.ScriptPathTweak(it) } ?: Crypto.TaprootTweak.KeyPathTweak
-        return pay2tr(internalKey, tweak)
+    public fun pay2tr(internalKey: XonlyPublicKey, scriptsRoot: ByteVector32): List<ScriptElt> {
+        return pay2tr(internalKey, Crypto.TaprootTweak.ScriptPathTweak(scriptsRoot))
     }
 
     /**

src/commonTest/kotlin/fr/acinq/bitcoin/TaprootTestsCommon.kt

@@ -30,7 +30,7 @@ class TaprootTestsCommon {
         val (_, master) = DeterministicWallet.ExtendedPrivateKey.decode("tprv8ZgxMBicQKsPeQQADibg4WF7mEasy3piWZUHyThAzJCPNgMHDVYhTCVfev3jFbDhcYm4GimeFMbbi9z1d9rfY1aL5wfJ9mNebQ4thJ62EJb")
         val key = DeterministicWallet.derivePrivateKey(master, "86'/1'/0'/0/1")
         val internalKey = key.publicKey.xOnly()
-        val script = Script.pay2tr(internalKey, scripts = null)
+        val script = Script.pay2tr(internalKey, Crypto.TaprootTweak.KeyPathTweak)
         val outputKey = internalKey.outputKey(Crypto.TaprootTweak.KeyPathTweak).first
         assertEquals("tb1phlhs7afhqzkgv0n537xs939s687826vn8l24ldkrckvwsnlj3d7qj6u57c", internalKey.p2trAddress(Block.Testnet3GenesisBlock.hash))
 
@@ -79,7 +79,7 @@ class TaprootTestsCommon {
         val tx = Transaction.read(
             "02000000000101bf77ef36f2c0f32e0822cef0514948254997495a34bfba7dd4a73aabfcbb87900000000000fdffffff02c2c2000000000000160014b5c3dbfeb8e7d0c809c3ba3f815fd430777ef4be50c30000000000002251208c5db7f797196d6edc4dd7df6048f4ea6b883a6af6af032342088f436543790f0140583f758bea307216e03c1f54c3c6088e8923c8e1c89d96679fb00de9e808a79d0fba1cc3f9521cb686e8f43fb37cc6429f2e1480c70cc25ecb4ac0dde8921a01f1f70000"
         )
-        assertEquals(Script.pay2tr(internalKey, scripts = null), Script.parse(tx.txOut[1].publicKeyScript))
+        assertEquals(Script.pay2tr(internalKey, Crypto.TaprootTweak.KeyPathTweak), Script.parse(tx.txOut[1].publicKeyScript))
 
         // we want to spend
         val outputScript = addressToPublicKeyScript(Block.Testnet3GenesisBlock.hash, "tb1pn3g330w4n5eut7d4vxq0pp303267qc6vg8d2e0ctjuqre06gs3yqnc5yx0").right!!

src/commonTest/kotlin/fr/acinq/bitcoin/psbt/PsbtTestsCommon.kt

@@ -1485,9 +1485,9 @@ class PsbtTestsCommon {
         // We make sure our utxos come from transactions with multiple outputs and are at different indices.
         val utxos = listOf(
             // @formatter:off
-            Transaction(version = 2, txIn = listOf(), txOut = listOf(TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(100_000.sat(), Script.pay2tr(getPublicKey(0), scripts = null))), lockTime = 0),
-            Transaction(version = 2, txIn = listOf(), txOut = listOf(TxOut(110_000.sat(), Script.pay2tr(getPublicKey(1), scripts = null)), TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef")))), lockTime = 0),
-            Transaction(version = 2, txIn = listOf(), txOut = listOf(TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(200_000.sat(), Script.pay2tr(getPublicKey(2), scripts = null))), lockTime = 0),
+            Transaction(version = 2, txIn = listOf(), txOut = listOf(TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(100_000.sat(), Script.pay2tr(getPublicKey(0), Crypto.TaprootTweak.KeyPathTweak))), lockTime = 0),
+            Transaction(version = 2, txIn = listOf(), txOut = listOf(TxOut(110_000.sat(), Script.pay2tr(getPublicKey(1), Crypto.TaprootTweak.KeyPathTweak)), TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef")))), lockTime = 0),
+            Transaction(version = 2, txIn = listOf(), txOut = listOf(TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(200_000.sat(), Script.pay2tr(getPublicKey(2), Crypto.TaprootTweak.KeyPathTweak))), lockTime = 0),
             Transaction(version = 2, txIn = listOf(), txOut = listOf(TxOut(5_000.sat(), Script.pay2wsh(ByteVector("deadbeef"))), TxOut(50_000.sat(), Script.pay2pkh(p2pkhPriv.publicKey()))), lockTime = 0),
             // @formatter:on
         )

src/commonTest/kotlin/fr/acinq/bitcoin/reference/BIP341TestsCommon.kt

@@ -89,12 +89,13 @@ class BIP341TestsCommon {
             }
 
             val intermediary = it.jsonObject["intermediary"]!!.jsonObject
-            val (tweakedKey, _) = internalPubkey.outputKey(scriptTree?.hash()?.let { Crypto.TaprootTweak.ScriptPathTweak(it) } ?: Crypto.TaprootTweak.KeyPathTweak)
+            val tweak = scriptTree?.hash()?.let { Crypto.TaprootTweak.ScriptPathTweak(it) } ?: Crypto.TaprootTweak.KeyPathTweak
+            val (tweakedKey, _) = internalPubkey.outputKey(tweak)
             scriptTree?.let { assertEquals(ByteVector32(intermediary["merkleRoot"]!!.jsonPrimitive.content), it.hash()) }
             assertEquals(ByteVector32(intermediary["tweakedPubkey"]!!.jsonPrimitive.content), tweakedKey.value)
 
             val expected = it.jsonObject["expected"]!!.jsonObject
-            val script = Script.pay2tr(internalPubkey, scriptTree)
+            val script = Script.pay2tr(internalPubkey, tweak)
             assertEquals(ByteVector(expected["scriptPubKey"]!!.jsonPrimitive.content), Script.write(script).byteVector())
             val bip350Address = Bech32.encodeWitnessAddress("bc", 1.toByte(), tweakedKey.value.toByteArray())
             assertEquals(expected["bip350Address"]!!.jsonPrimitive.content, bip350Address)

src/commonTest/kotlin/fr/acinq/bitcoin/reference/ScriptTestsCommon.kt

@@ -193,7 +193,7 @@ class ScriptTestsCommon {
             }
             val witness = ScriptWitness(witnessStack)
             val scriptPubKey = if (scriptPubKeyText == "0x51 0x20 #TAPROOTOUTPUT#") {
-                Script.write(Script.pay2tr(priv.xOnlyPublicKey(), leaf))
+                Script.write(Script.pay2tr(priv.xOnlyPublicKey(), leaf?.let { Crypto.TaprootTweak.ScriptPathTweak(it.hash()) } ?: Crypto.TaprootTweak.KeyPathTweak))
             } else {
                 parseFromText(scriptPubKeyText)
             }