Merge bitcoin#17237: wallet: LearnRelatedScripts only if KeepDestination

3958295 wallet: LearnRelatedScripts only if KeepDestination (João Barbosa)
55295fb wallet: Lock address type in ReserveDestination (João Barbosa)

Pull request description:

  Only mutates the wallet if the reserved key is kept.

  First commit is a refactor that makes the address type a class member.

  The second commit moves `LearnRelatedScripts` from `GetReservedDestination` to `KeepDestination` to avoid an unnecessary call to `AddCScript` - which in turn prevents multiple entries of the same script in the wallet DB.

ACKs for top commit:
  achow101:
    Re-ACK 3958295
  Sjors:
    ACK 3958295
  ryanofsky:
    Code review ACK 3958295. I like this change. The new behavior makes more sense, and the change makes the code clearer, since the current LearnRelatedScripts call is hard to understand and explain. (Personally, I'd like it if this PR were merged before bitcoin#17373 or that PR was rebased on top of this one so it would be less confusing.)
  meshcollider:
    utACK 3958295

Tree-SHA512: 49a5f4b022b28042ad37ea309b28378a3983cb904e234a25795b5a360356652e0f8e60f15e3e64d85094ea63af9be01812d90ccfc08ca4f1dd927fdd8566e33f

src/wallet/wallet.cpp

@@ -2610,7 +2610,8 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
                          int& nChangePosInOut, std::string& strFailReason, const CCoinControl& coin_control, bool sign)
 {
     CAmount nValue = 0;
-    ReserveDestination reservedest(this);
+    const OutputType change_type = TransactionChangeType(coin_control.m_change_type ? *coin_control.m_change_type : m_default_change_type, vecSend);
+    ReserveDestination reservedest(this, change_type);
     int nChangePosRequest = nChangePosInOut;
     unsigned int nSubtractFeeFromAmount = 0;
     for (const auto& recipient : vecSend)
@@ -2669,8 +2670,7 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
                     return false;
                 }
                 CTxDestination dest;
-                const OutputType change_type = TransactionChangeType(coin_control.m_change_type ? *coin_control.m_change_type : m_default_change_type, vecSend);
-                bool ret = reservedest.GetReservedDestination(change_type, dest, true);
+                bool ret = reservedest.GetReservedDestination(dest, true);
                 if (!ret)
                 {
                     strFailReason = "Keypool ran out, please call keypoolrefill first";
@@ -3197,8 +3197,8 @@ bool CWallet::GetNewChangeDestination(const OutputType type, CTxDestination& des
 
     m_spk_man->TopUp();
 
-    ReserveDestination reservedest(this);
-    if (!reservedest.GetReservedDestination(type, dest, true)) {
+    ReserveDestination reservedest(this, type);
+    if (!reservedest.GetReservedDestination(dest, true)) {
         error = "Error: Keypool ran out, please call keypoolrefill first";
         return false;
     }
@@ -3364,7 +3364,7 @@ std::set<CTxDestination> CWallet::GetLabelAddresses(const std::string& label) co
     return result;
 }
 
-bool ReserveDestination::GetReservedDestination(const OutputType type, CTxDestination& dest, bool internal)
+bool ReserveDestination::GetReservedDestination(CTxDestination& dest, bool internal)
 {
     m_spk_man = pwallet->GetLegacyScriptPubKeyMan();
     if (!m_spk_man) {
@@ -3385,16 +3385,17 @@ bool ReserveDestination::GetReservedDestination(const OutputType type, CTxDestin
         fInternal = keypool.fInternal;
     }
     assert(vchPubKey.IsValid());
-    m_spk_man->LearnRelatedScripts(vchPubKey, type);
     address = GetDestinationForKey(vchPubKey, type);
     dest = address;
     return true;
 }
 
 void ReserveDestination::KeepDestination()
 {
-    if (nIndex != -1)
+    if (nIndex != -1) {
         m_spk_man->KeepDestination(nIndex);
+        m_spk_man->LearnRelatedScripts(vchPubKey, type);
+    }
     nIndex = -1;
     vchPubKey = CPubKey();
     address = CNoDestination();

src/wallet/wallet.h

@@ -141,8 +141,9 @@ class ReserveDestination : public CReserveScript
 {
 protected:
     //! The wallet to reserve from
-    CWallet* pwallet;
+    CWallet* const pwallet;
     LegacyScriptPubKeyMan* m_spk_man{nullptr};
+    OutputType const type;
     //! The index of the address's key in the keypool
     int64_t nIndex{-1};
     //! The public key for the address
@@ -154,10 +155,9 @@ class ReserveDestination : public CReserveScript
 
 public:
     //! Construct a ReserveDestination object. This does NOT reserve an address yet
-    explicit ReserveDestination(CWallet* pwalletIn)
-    {
-        pwallet = pwalletIn;
-    }
+    explicit ReserveDestination(CWallet* pwallet, OutputType type)
+      : pwallet(pwallet)
+      , type(type) { }
 
     ReserveDestination(const ReserveDestination&) = delete;
     ReserveDestination& operator=(const ReserveDestination&) = delete;
@@ -169,7 +169,7 @@ class ReserveDestination : public CReserveScript
     }
 
     //! Reserve an address
-    bool GetReservedDestination(const OutputType type, CTxDestination& pubkey, bool internal);
+    bool GetReservedDestination(CTxDestination& pubkey, bool internal);
     //! Return reserved address
     void ReturnDestination();
     //! Keep the address. Do not return it's key to the keypool when this object goes out of scope