From 31df02a07091dbd5e0b315c8e5695e808f3a5505 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter@wuille.net>
Date: Sun, 23 May 2021 18:00:18 -0700
Subject: [PATCH] Change Solver() output for WITNESS_V1_TAPROOT

This is just a small simplification to prepare for the follow-up instruction
of a CTxDestination variant for taproot outputs.

In the old code, WITNESS_V1_TAPROOT and WITNESS_UNKNOWN both produced
{version, program} as Solver() output. Change this so that WITNESS_V1_TAPROOT
produces just {program}, like WITNESS_V0_* do.
---
 src/script/standard.cpp            | 16 ++++++++++++----
 src/test/script_standard_tests.cpp |  5 ++---
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/script/standard.cpp b/src/script/standard.cpp
index 364fac3c84..540aa0f2d9 100644
--- a/src/script/standard.cpp
+++ b/src/script/standard.cpp
@@ -155,15 +155,14 @@ TxoutType Solver(const CScript& scriptPubKey, std::vector<std::vector<unsigned c
     std::vector<unsigned char> witnessprogram;
     if (scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
         if (witnessversion == 0 && witnessprogram.size() == WITNESS_V0_KEYHASH_SIZE) {
-            vSolutionsRet.push_back(witnessprogram);
+            vSolutionsRet.push_back(std::move(witnessprogram));
             return TxoutType::WITNESS_V0_KEYHASH;
         }
         if (witnessversion == 0 && witnessprogram.size() == WITNESS_V0_SCRIPTHASH_SIZE) {
-            vSolutionsRet.push_back(witnessprogram);
+            vSolutionsRet.push_back(std::move(witnessprogram));
             return TxoutType::WITNESS_V0_SCRIPTHASH;
         }
         if (witnessversion == 1 && witnessprogram.size() == WITNESS_V1_TAPROOT_SIZE) {
-            vSolutionsRet.push_back(std::vector<unsigned char>{(unsigned char)witnessversion});
             vSolutionsRet.push_back(std::move(witnessprogram));
             return TxoutType::WITNESS_V1_TAPROOT;
         }
@@ -242,8 +241,17 @@ bool ExtractDestination(const CScript& scriptPubKey, CTxDestination& addressRet)
         addressRet = hash;
         return true;
     }
-    case TxoutType::WITNESS_UNKNOWN:
     case TxoutType::WITNESS_V1_TAPROOT: {
+        /* For now, no WitnessV1Taproot variant in CTxDestination exists, so map
+         * this to WitnessUnknown. */
+        WitnessUnknown unk;
+        unk.version = 1;
+        std::copy(vSolutions[0].begin(), vSolutions[0].end(), unk.program);
+        unk.length = vSolutions[0].size();
+        addressRet = unk;
+        return true;
+    }
+    case TxoutType::WITNESS_UNKNOWN: {
         WitnessUnknown unk;
         unk.version = vSolutions[0][0];
         std::copy(vSolutions[1].begin(), vSolutions[1].end(), unk.program);
diff --git a/src/test/script_standard_tests.cpp b/src/test/script_standard_tests.cpp
index 44fbfa5970..950f3b970a 100644
--- a/src/test/script_standard_tests.cpp
+++ b/src/test/script_standard_tests.cpp
@@ -111,9 +111,8 @@ BOOST_AUTO_TEST_CASE(script_standard_Solver_success)
     s.clear();
     s << OP_1 << ToByteVector(uint256::ZERO);
     BOOST_CHECK_EQUAL(Solver(s, solutions), TxoutType::WITNESS_V1_TAPROOT);
-    BOOST_CHECK_EQUAL(solutions.size(), 2U);
-    BOOST_CHECK(solutions[0] == std::vector<unsigned char>{1});
-    BOOST_CHECK(solutions[1] == ToByteVector(uint256::ZERO));
+    BOOST_CHECK_EQUAL(solutions.size(), 1U);
+    BOOST_CHECK(solutions[0] == ToByteVector(uint256::ZERO));
 
     // TxoutType::WITNESS_UNKNOWN
     s.clear();