Wallet: Avoid using change types newer than user's preferred address type

Author: luke-jr

src/wallet/test/util.cpp

@@ -20,6 +20,7 @@ std::unique_ptr<CWallet> CreateSyncedWallet(interfaces::Chain& chain, CChain& cc
     {
         LOCK2(wallet->cs_wallet, ::cs_main);
         wallet->SetLastBlockProcessed(cchain.Height(), cchain.Tip()->GetBlockHash());
+        wallet->m_default_address_type = OutputType::BECH32M;
     }
     wallet->LoadWallet();
     {

src/wallet/wallet.cpp

@@ -2267,7 +2267,7 @@ OutputType CWallet::TransactionChangeType(const std::optional<OutputType>& chang
     }
 
     const bool has_bech32m_spkman(GetScriptPubKeyMan(OutputType::BECH32M, /*internal=*/true));
-    if (has_bech32m_spkman && any_tr) {
+    if (has_bech32m_spkman && any_tr && m_default_address_type == OutputType::BECH32M) {
         // Currently tr is the only type supported by the BECH32M spkman
         return OutputType::BECH32M;
     }
@@ -2287,6 +2287,16 @@ OutputType CWallet::TransactionChangeType(const std::optional<OutputType>& chang
         // Currently pkh is the only type supported by the LEGACY spkman
         return OutputType::LEGACY;
     }
+    if (!GetScriptPubKeyMan(m_default_address_type, /*internal=*/true)) {
+        // Default type not available, so look for anything else to fallback to
+        // NOTE: Sane behaviour assumes OUTPUT_TYPES is sorted oldest to newest
+        for (const auto& ot : OUTPUT_TYPES) {
+            if (GetScriptPubKeyMan(ot, /*internal=*/true)) {
+                return ot;
+            }
+        }
+    }
+    return m_default_address_type;
 
     if (has_bech32m_spkman) {
         return OutputType::BECH32M;

test/functional/wallet_taproot.py

@@ -194,6 +194,8 @@ def set_test_params(self):
         self.num_nodes = 2
         self.setup_clean_chain = True
         self.extra_args = [['-keypool=100'], ['-keypool=100']]
+        for ea in self.extra_args:
+            ea.append('-addresstype=bech32m')
         self.supports_cli = False
 
     def skip_test_if_missing_module(self):