Merge bitcoin/bitcoin#25218: refactor: introduce generic 'Result' class and connect it to CreateTransaction and GetNewDestination

111ea3ab711414236f8678566a7884d48619b2d8 wallet: refactor GetNewDestination, use BResult (furszy)
22351725bc4c5eb63ee45f607374bbf2d76e2b8c send: refactor CreateTransaction flow to return a BResult<CTransactionRef> (furszy)
198fcca162f4d2f877feab485e629ff89818ff56 wallet: refactor, include 'FeeCalculation' inside 'CreatedTransactionResult' (furszy)
7a45c33d1f8a758850cf8e7bd6ad508939ba5c0d Introduce generic 'Result' class (furszy)

Pull request description:

  Based on a common function signature pattern that we have all around the sources:
  ```cpp
  bool doSomething(arg1, arg2, arg3, arg4, &result_obj, &error_string) {
      // do something...
      if (error) {
          error_string = "something bad happened";
          return false;
      }

      result = goodResult;
      return true;
  }
  ```

  Introduced a generic class `BResult` that encapsulate the function boolean result, the result object (in case of having it) and, in case of failure, the string error reason.

  Obtaining in this way cleaner function signatures and removing boilerplate code:

  ```cpp
  BResult<Obj> doSomething(arg1, arg2, arg3, arg4) {
      // do something...
      if (error) return "something bad happened";

      return goodResult;
  }
  ```

  Same cleanup applies equally to the function callers' side as well. There is no longer need to add the error string and the result object declarations before calling the function:

  Before:
  ```cpp
  Obj result_obj;
  std::string error_string;
  if (!doSomething(arg1, arg2, arg3, arg4, result_obj, error_string)) {
      LogPrintf("Error: %s", error_string);
  }
  return result_obj;
  ```

  Now:
  ```cpp
  BResult<Obj> op_res = doSomething(arg1, arg2, arg3, arg4);
  if (!op_res) {
      LogPrintf("Error: %s", op_res.GetError());
  }
  return op_res.GetObjResult();
  ```

  ### Initial Implementation:

  Have connected this new concept to two different flows for now:

  1) The `CreateTransaction` flow. --> 7ba2b87c
  2) The `GetNewDestination` flow. --> bcee0912

  Happy note: even when introduced a new class into the sources, the amount of lines removed is almost equal to added ones :).

  Extra note: this work is an extended version (and a decoupling) of the work that is inside #24845 (which does not contain the `GetNewDestination` changes nor the inclusion of the `FeeCalculation` field inside `CreatedTransactionResult`).

ACKs for top commit:
  achow101:
    ACK 111ea3ab711414236f8678566a7884d48619b2d8
  w0xlt:
    reACK https://github.com/bitcoin/bitcoin/pull/25218/commits/111ea3ab711414236f8678566a7884d48619b2d8
  theStack:
    re-ACK 111ea3ab711414236f8678566a7884d48619b2d8
  MarcoFalke:
    review ACK 111ea3ab711414236f8678566a7884d48619b2d8 🎏

Tree-SHA512: 6d84d901a4cb923727067f25ff64542a40edd1ea84fdeac092312ac684c34e3688a52ac5eb012717d2b73f4cb742b9d78e458eb0e9cb9d6d72a916395be91f69

14 files changed, 138 insertions, 170 deletions

diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index 5e70ed4a30..43fdcee48d 100644
--- a/src/wallet/feebumper.cpp
+++ b/src/wallet/feebumper.cpp
@@ -219,19 +219,18 @@ Result CreateRateBumpTransaction(CWallet& wallet, const uint256& txid, const CCo
     new_coin_control.m_min_depth = 1;
 
     constexpr int RANDOM_CHANGE_POSITION = -1;
-    bilingual_str fail_reason;
-    FeeCalculation fee_calc_out;
-    std::optional<CreatedTransactionResult> txr = CreateTransaction(wallet, recipients, RANDOM_CHANGE_POSITION, fail_reason, new_coin_control, fee_calc_out, false);
-    if (!txr) {
-        errors.push_back(Untranslated("Unable to create transaction.") + Untranslated(" ") + fail_reason);
+    auto res = CreateTransaction(wallet, recipients, RANDOM_CHANGE_POSITION, new_coin_control, false);
+    if (!res) {
+        errors.push_back(Untranslated("Unable to create transaction.") + Untranslated(" ") + res.GetError());
         return Result::WALLET_ERROR;
     }
 
+    const auto& txr = res.GetObj();
     // Write back new fee if successful
-    new_fee = txr->fee;
+    new_fee = txr.fee;
 
     // Write back transaction
-    mtx = CMutableTransaction(*txr->tx);
+    mtx = CMutableTransaction(*txr.tx);
 
     return Result::OK;
 }
diff --git a/src/wallet/interfaces.cpp b/src/wallet/interfaces.cpp
index 327276f2ed..547d972c8d 100644
--- a/src/wallet/interfaces.cpp
+++ b/src/wallet/interfaces.cpp
@@ -146,11 +146,10 @@ public:
     void abortRescan() override { m_wallet->AbortRescan(); }
     bool backupWallet(const std::string& filename) override { return m_wallet->BackupWallet(filename); }
     std::string getWalletName() override { return m_wallet->GetName(); }
-    bool getNewDestination(const OutputType type, const std::string label, CTxDestination& dest) override
+    BResult<CTxDestination> getNewDestination(const OutputType type, const std::string label) override
     {
         LOCK(m_wallet->cs_wallet);
-        bilingual_str error;
-        return m_wallet->GetNewDestination(type, label, dest, error);
+        return m_wallet->GetNewDestination(type, label);
     }
     bool getPubKey(const CScript& script, const CKeyID& address, CPubKey& pub_key) override
     {
@@ -250,22 +249,21 @@ public:
         LOCK(m_wallet->cs_wallet);
         return m_wallet->ListLockedCoins(outputs);
     }
-    CTransactionRef createTransaction(const std::vector<CRecipient>& recipients,
+    BResult<CTransactionRef> createTransaction(const std::vector<CRecipient>& recipients,
         const CCoinControl& coin_control,
         bool sign,
         int& change_pos,
-        CAmount& fee,
-        bilingual_str& fail_reason) override
+        CAmount& fee) override
     {
         LOCK(m_wallet->cs_wallet);
-        FeeCalculation fee_calc_out;
-        std::optional<CreatedTransactionResult> txr = CreateTransaction(*m_wallet, recipients, change_pos,
-                fail_reason, coin_control, fee_calc_out, sign);
-        if (!txr) return {};
-        fee = txr->fee;
-        change_pos = txr->change_pos;
+        const auto& res = CreateTransaction(*m_wallet, recipients, change_pos,
+                                     coin_control, sign);
+        if (!res) return res.GetError();
+        const auto& txr = res.GetObj();
+        fee = txr.fee;
+        change_pos = txr.change_pos;
 
-        return txr->tx;
+        return txr.tx;
     }
     void commitTransaction(CTransactionRef tx,
         WalletValueMap value_map,
diff --git a/src/wallet/rpc/addresses.cpp b/src/wallet/rpc/addresses.cpp
index da4cc44ee6..9428d049de 100644
--- a/src/wallet/rpc/addresses.cpp
+++ b/src/wallet/rpc/addresses.cpp
@@ -58,13 +58,12 @@ RPCHelpMan getnewaddress()
         output_type = parsed.value();
     }
 
-    CTxDestination dest;
-    bilingual_str error;
-    if (!pwallet->GetNewDestination(output_type, label, dest, error)) {
-        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, error.original);
+    auto op_dest = pwallet->GetNewDestination(output_type, label);
+    if (!op_dest) {
+        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, op_dest.GetError().original);
     }
 
-    return EncodeDestination(dest);
+    return EncodeDestination(op_dest.GetObj());
 },
     };
 }
@@ -106,12 +105,11 @@ RPCHelpMan getrawchangeaddress()
         output_type = parsed.value();
     }
 
-    CTxDestination dest;
-    bilingual_str error;
-    if (!pwallet->GetNewChangeDestination(output_type, dest, error)) {
-        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, error.original);
+    auto op_dest = pwallet->GetNewChangeDestination(output_type);
+    if (!op_dest) {
+        throw JSONRPCError(RPC_WALLET_KEYPOOL_RAN_OUT, op_dest.GetError().original);
     }
-    return EncodeDestination(dest);
+    return EncodeDestination(op_dest.GetObj());
 },
     };
 }
diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index 0e8cee5db8..22c1f2bdc2 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/src/wallet/rpc/spend.cpp
@@ -156,18 +156,16 @@ UniValue SendMoney(CWallet& wallet, const CCoinControl &coin_control, std::vecto
 
     // Send
     constexpr int RANDOM_CHANGE_POSITION = -1;
-    bilingual_str error;
-    FeeCalculation fee_calc_out;
-    std::optional<CreatedTransactionResult> txr = CreateTransaction(wallet, recipients, RANDOM_CHANGE_POSITION, error, coin_control, fee_calc_out, true);
-    if (!txr) {
-        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, error.original);
+    auto res = CreateTransaction(wallet, recipients, RANDOM_CHANGE_POSITION, coin_control, true);
+    if (!res) {
+        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, res.GetError().original);
     }
-    CTransactionRef tx = txr->tx;
+    const CTransactionRef& tx = res.GetObj().tx;
     wallet.CommitTransaction(tx, std::move(map_value), {} /* orderForm */);
     if (verbose) {
         UniValue entry(UniValue::VOBJ);
         entry.pushKV("txid", tx->GetHash().GetHex());
-        entry.pushKV("fee_reason", StringForFeeReason(fee_calc_out.reason));
+        entry.pushKV("fee_reason", StringForFeeReason(res.GetObj().fee_calc.reason));
         return entry;
     }
     return tx->GetHash().GetHex();
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index 1fec82a485..bba31dfe0b 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -21,26 +21,22 @@ namespace wallet {
 //! Value for the first BIP 32 hardened derivation. Can be used as a bit mask and as a value. See BIP 32 for more details.
 const uint32_t BIP32_HARDENED_KEY_LIMIT = 0x80000000;
 
-bool LegacyScriptPubKeyMan::GetNewDestination(const OutputType type, CTxDestination& dest, bilingual_str& error)
+BResult<CTxDestination> LegacyScriptPubKeyMan::GetNewDestination(const OutputType type)
 {
     if (LEGACY_OUTPUT_TYPES.count(type) == 0) {
-        error = _("Error: Legacy wallets only support the \"legacy\", \"p2sh-segwit\", and \"bech32\" address types");
-        return false;
+        return _("Error: Legacy wallets only support the \"legacy\", \"p2sh-segwit\", and \"bech32\" address types");;
     }
     assert(type != OutputType::BECH32M);
 
     LOCK(cs_KeyStore);
-    error.clear();
 
     // Generate a new key that is added to wallet
     CPubKey new_key;
     if (!GetKeyFromPool(new_key, type)) {
-        error = _("Error: Keypool ran out, please call keypoolrefill first");
-        return false;
+        return _("Error: Keypool ran out, please call keypoolrefill first");
     }
     LearnRelatedScripts(new_key, type);
-    dest = GetDestinationForKey(new_key, type);
-    return true;
+    return GetDestinationForKey(new_key, type);
 }
 
 typedef std::vector<unsigned char> valtype;
@@ -1658,12 +1654,11 @@ std::set<CKeyID> LegacyScriptPubKeyMan::GetKeys() const
     return set_address;
 }
 
-bool DescriptorScriptPubKeyMan::GetNewDestination(const OutputType type, CTxDestination& dest, bilingual_str& error)
+BResult<CTxDestination> DescriptorScriptPubKeyMan::GetNewDestination(const OutputType type)
 {
     // Returns true if this descriptor supports getting new addresses. Conditions where we may be unable to fetch them (e.g. locked) are caught later
     if (!CanGetAddresses()) {
-        error = _("No addresses available");
-        return false;
+        return _("No addresses available");
     }
     {
         LOCK(cs_desc_man);
@@ -1681,15 +1676,14 @@ bool DescriptorScriptPubKeyMan::GetNewDestination(const OutputType type, CTxDest
         std::vector<CScript> scripts_temp;
         if (m_wallet_descriptor.range_end <= m_max_cached_index && !TopUp(1)) {
             // We can't generate anymore keys
-            error = _("Error: Keypool ran out, please call keypoolrefill first");
-            return false;
+            return _("Error: Keypool ran out, please call keypoolrefill first");
         }
         if (!m_wallet_descriptor.descriptor->ExpandFromCache(m_wallet_descriptor.next_index, m_wallet_descriptor.cache, scripts_temp, out_keys)) {
             // We can't generate anymore keys
-            error = _("Error: Keypool ran out, please call keypoolrefill first");
-            return false;
+            return _("Error: Keypool ran out, please call keypoolrefill first");
         }
 
+        CTxDestination dest;
         std::optional<OutputType> out_script_type = m_wallet_descriptor.descriptor->GetOutputType();
         if (out_script_type && out_script_type == type) {
             ExtractDestination(scripts_temp[0], dest);
@@ -1698,7 +1692,7 @@ bool DescriptorScriptPubKeyMan::GetNewDestination(const OutputType type, CTxDest
         }
         m_wallet_descriptor.next_index++;
         WalletBatch(m_storage.GetDatabase()).WriteDescriptor(GetID(), m_wallet_descriptor);
-        return true;
+        return dest;
     }
 }
 
@@ -1769,9 +1763,14 @@ bool DescriptorScriptPubKeyMan::Encrypt(const CKeyingMaterial& master_key, Walle
 bool DescriptorScriptPubKeyMan::GetReservedDestination(const OutputType type, bool internal, CTxDestination& address, int64_t& index, CKeyPool& keypool, bilingual_str& error)
 {
     LOCK(cs_desc_man);
-    bool result = GetNewDestination(type, address, error);
+    auto op_dest = GetNewDestination(type);
     index = m_wallet_descriptor.next_index - 1;
-    return result;
+    if (op_dest) {
+        address = op_dest.GetObj();
+    } else {
+        error = op_dest.GetError();
+    }
+    return op_dest.HasRes();
 }
 
 void DescriptorScriptPubKeyMan::ReturnDestination(int64_t index, bool internal, const CTxDestination& addr)
diff --git a/src/wallet/scriptpubkeyman.h b/src/wallet/scriptpubkeyman.h
index ad924791af..eebc05330f 100644
--- a/src/wallet/scriptpubkeyman.h
+++ b/src/wallet/scriptpubkeyman.h
@@ -11,6 +11,7 @@
 #include <script/standard.h>
 #include <util/error.h>
 #include <util/message.h>
+#include <util/result.h>
 #include <util/time.h>
 #include <wallet/crypter.h>
 #include <wallet/ismine.h>
@@ -171,7 +172,7 @@ protected:
 public:
     explicit ScriptPubKeyMan(WalletStorage& storage) : m_storage(storage) {}
     virtual ~ScriptPubKeyMan() {};
-    virtual bool GetNewDestination(const OutputType type, CTxDestination& dest, bilingual_str& error) { return false; }
+    virtual BResult<CTxDestination> GetNewDestination(const OutputType type) { return Untranslated("Not supported"); }
     virtual isminetype IsMine(const CScript& script) const { return ISMINE_NO; }
 
     //! Check that the given decryption key is valid for this ScriptPubKeyMan, i.e. it decrypts all of the keys handled by it.
@@ -359,7 +360,7 @@ private:
 public:
     using ScriptPubKeyMan::ScriptPubKeyMan;
 
-    bool GetNewDestination(const OutputType type, CTxDestination& dest, bilingual_str& error) override;
+    BResult<CTxDestination> GetNewDestination(const OutputType type) override;
     isminetype IsMine(const CScript& script) const override;
 
     bool CheckDecryptionKey(const CKeyingMaterial& master_key, bool accept_no_keys = false) override;
@@ -567,7 +568,7 @@ public:
 
     mutable RecursiveMutex cs_desc_man;
 
-    bool GetNewDestination(const OutputType type, CTxDestination& dest, bilingual_str& error) override;
+    BResult<CTxDestination> GetNewDestination(const OutputType type) override;
     isminetype IsMine(const CScript& script) const override;
 
     bool CheckDecryptionKey(const CKeyingMaterial& master_key, bool accept_no_keys = false) override;
diff --git a/src/wallet/spend.cpp b/src/wallet/spend.cpp
index 21007f5a92..9be29c4709 100644
--- a/src/wallet/spend.cpp
+++ b/src/wallet/spend.cpp
@@ -652,19 +652,16 @@ static void DiscourageFeeSniping(CMutableTransaction& tx, FastRandomContext& rng
     }
 }
 
-static std::optional<CreatedTransactionResult> CreateTransactionInternal(
+static BResult<CreatedTransactionResult> CreateTransactionInternal(
         CWallet& wallet,
         const std::vector<CRecipient>& vecSend,
         int change_pos,
-        bilingual_str& error,
         const CCoinControl& coin_control,
-        FeeCalculation& fee_calc_out,
         bool sign) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
 {
     AssertLockHeld(wallet.cs_wallet);
 
     // out variables, to be packed into returned result structure
-    CTransactionRef tx;
     CAmount nFeeRet;
     int nChangePosInOut = change_pos;
 
@@ -693,6 +690,7 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
 
     // Create change script that will be used if we need change
     CScript scriptChange;
+    bilingual_str error; // possible error str
 
     // coin control: send change to custom address
     if (!std::get_if<CNoDestination>(&coin_control.destChange)) {
@@ -740,13 +738,11 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
     // Do not, ever, assume that it's fine to change the fee rate if the user has explicitly
     // provided one
     if (coin_control.m_feerate && coin_selection_params.m_effective_feerate > *coin_control.m_feerate) {
-        error = strprintf(_("Fee rate (%s) is lower than the minimum fee rate setting (%s)"), coin_control.m_feerate->ToString(FeeEstimateMode::SAT_VB), coin_selection_params.m_effective_feerate.ToString(FeeEstimateMode::SAT_VB));
-        return std::nullopt;
+        return strprintf(_("Fee rate (%s) is lower than the minimum fee rate setting (%s)"), coin_control.m_feerate->ToString(FeeEstimateMode::SAT_VB), coin_selection_params.m_effective_feerate.ToString(FeeEstimateMode::SAT_VB));
     }
     if (feeCalc.reason == FeeReason::FALLBACK && !wallet.m_allow_fallback_fee) {
         // eventually allow a fallback fee
-        error = _("Fee estimation failed. Fallbackfee is disabled. Wait a few blocks or enable -fallbackfee.");
-        return std::nullopt;
+        return _("Fee estimation failed. Fallbackfee is disabled. Wait a few blocks or enable -fallbackfee.");
     }
 
     // Calculate the cost of change
@@ -771,10 +767,8 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
             coin_selection_params.tx_noinputs_size += ::GetSerializeSize(txout, PROTOCOL_VERSION);
         }
 
-        if (IsDust(txout, wallet.chain().relayDustFee()))
-        {
-            error = _("Transaction amount too small");
-            return std::nullopt;
+        if (IsDust(txout, wallet.chain().relayDustFee())) {
+            return _("Transaction amount too small");
         }
         txNew.vout.push_back(txout);
     }
@@ -795,8 +789,7 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
     // Choose coins to use
     std::optional<SelectionResult> result = SelectCoins(wallet, res_available_coins.coins, /*nTargetValue=*/selection_target, coin_control, coin_selection_params);
     if (!result) {
-        error = _("Insufficient funds");
-        return std::nullopt;
+        return _("Insufficient funds");
     }
     TRACE5(coin_selection, selected_coins, wallet.GetName().c_str(), GetAlgorithmName(result->m_algo).c_str(), result->m_target, result->GetWaste(), result->GetSelectedValue());
 
@@ -810,10 +803,8 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
         // Insert change txn at random position:
         nChangePosInOut = rng_fast.randrange(txNew.vout.size() + 1);
     }
-    else if ((unsigned int)nChangePosInOut > txNew.vout.size())
-    {
-        error = _("Transaction change output index out of range");
-        return std::nullopt;
+    else if ((unsigned int)nChangePosInOut > txNew.vout.size()) {
+        return _("Transaction change output index out of range");
     }
 
     assert(nChangePosInOut != -1);
@@ -840,8 +831,7 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
     TxSize tx_sizes = CalculateMaximumSignedTxSize(CTransaction(txNew), &wallet, &coin_control);
     int nBytes = tx_sizes.vsize;
     if (nBytes == -1) {
-        error = _("Missing solving data for estimating transaction size");
-        return std::nullopt;
+        return _("Missing solving data for estimating transaction size");
     }
     nFeeRet = coin_selection_params.m_effective_feerate.GetFee(nBytes);
 
@@ -901,11 +891,10 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
                 // Error if this output is reduced to be below dust
                 if (IsDust(txout, wallet.chain().relayDustFee())) {
                     if (txout.nValue < 0) {
-                        error = _("The transaction amount is too small to pay the fee");
+                        return _("The transaction amount is too small to pay the fee");
                     } else {
-                        error = _("The transaction amount is too small to send after the fee has been deducted");
+                        return _("The transaction amount is too small to send after the fee has been deducted");
                     }
-                    return std::nullopt;
                 }
             }
             ++i;
@@ -915,42 +904,37 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
 
     // Give up if change keypool ran out and change is required
     if (scriptChange.empty() && nChangePosInOut != -1) {
-        return std::nullopt;
+        return error;
     }
 
     if (sign && !wallet.SignTransaction(txNew)) {
-        error = _("Signing transaction failed");
-        return std::nullopt;
+        return _("Signing transaction failed");
     }
 
     // Return the constructed transaction data.
-    tx = MakeTransactionRef(std::move(txNew));
+    CTransactionRef tx = MakeTransactionRef(std::move(txNew));
 
     // Limit size
     if ((sign && GetTransactionWeight(*tx) > MAX_STANDARD_TX_WEIGHT) ||
         (!sign && tx_sizes.weight > MAX_STANDARD_TX_WEIGHT))
     {
-        error = _("Transaction too large");
-        return std::nullopt;
+        return _("Transaction too large");
     }
 
     if (nFeeRet > wallet.m_default_max_tx_fee) {
-        error = TransactionErrorString(TransactionError::MAX_FEE_EXCEEDED);
-        return std::nullopt;
+        return TransactionErrorString(TransactionError::MAX_FEE_EXCEEDED);
     }
 
     if (gArgs.GetBoolArg("-walletrejectlongchains", DEFAULT_WALLET_REJECT_LONG_CHAINS)) {
         // Lastly, ensure this tx will pass the mempool's chain limits
         if (!wallet.chain().checkChainLimits(tx)) {
-            error = _("Transaction has too long of a mempool chain");
-            return std::nullopt;
+            return _("Transaction has too long of a mempool chain");
         }
     }
 
     // Before we return success, we assume any change key will be used to prevent
     // accidental re-use.
     reservedest.KeepDestination();
-    fee_calc_out = feeCalc;
 
     wallet.WalletLogPrintf("Fee Calculation: Fee:%d Bytes:%u Tgt:%d (requested %d) Reason:\"%s\" Decay %.5f: Estimation: (%g - %g) %.2f%% %.1f/(%.1f %d mem %.1f out) Fail: (%g - %g) %.2f%% %.1f/(%.1f %d mem %.1f out)\n",
               nFeeRet, nBytes, feeCalc.returnedTarget, feeCalc.desiredTarget, StringForFeeReason(feeCalc.reason), feeCalc.est.decay,
@@ -960,52 +944,50 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
               feeCalc.est.fail.start, feeCalc.est.fail.end,
               (feeCalc.est.fail.totalConfirmed + feeCalc.est.fail.inMempool + feeCalc.est.fail.leftMempool) > 0.0 ? 100 * feeCalc.est.fail.withinTarget / (feeCalc.est.fail.totalConfirmed + feeCalc.est.fail.inMempool + feeCalc.est.fail.leftMempool) : 0.0,
               feeCalc.est.fail.withinTarget, feeCalc.est.fail.totalConfirmed, feeCalc.est.fail.inMempool, feeCalc.est.fail.leftMempool);
-    return CreatedTransactionResult(tx, nFeeRet, nChangePosInOut);
+    return CreatedTransactionResult(tx, nFeeRet, nChangePosInOut, feeCalc);
 }
 
-std::optional<CreatedTransactionResult> CreateTransaction(
+BResult<CreatedTransactionResult> CreateTransaction(
         CWallet& wallet,
         const std::vector<CRecipient>& vecSend,
         int change_pos,
-        bilingual_str& error,
         const CCoinControl& coin_control,
-        FeeCalculation& fee_calc_out,
         bool sign)
 {
     if (vecSend.empty()) {
-        error = _("Transaction must have at least one recipient");
-        return std::nullopt;
+        return _("Transaction must have at least one recipient");
     }
 
     if (std::any_of(vecSend.cbegin(), vecSend.cend(), [](const auto& recipient){ return recipient.nAmount < 0; })) {
-        error = _("Transaction amounts must not be negative");
-        return std::nullopt;
+        return _("Transaction amounts must not be negative");
     }
 
     LOCK(wallet.cs_wallet);
 
-    std::optional<CreatedTransactionResult> txr_ungrouped = CreateTransactionInternal(wallet, vecSend, change_pos, error, coin_control, fee_calc_out, sign);
-    TRACE4(coin_selection, normal_create_tx_internal, wallet.GetName().c_str(), txr_ungrouped.has_value(),
-           txr_ungrouped.has_value() ? txr_ungrouped->fee : 0, txr_ungrouped.has_value() ? txr_ungrouped->change_pos : 0);
-    if (!txr_ungrouped) return std::nullopt;
+    auto res = CreateTransactionInternal(wallet, vecSend, change_pos, coin_control, sign);
+    TRACE4(coin_selection, normal_create_tx_internal, wallet.GetName().c_str(), res.HasRes(),
+           res ? res.GetObj().fee : 0, res ? res.GetObj().change_pos : 0);
+    if (!res) return res;
+    const auto& txr_ungrouped = res.GetObj();
     // try with avoidpartialspends unless it's enabled already
-    if (txr_ungrouped->fee > 0 /* 0 means non-functional fee rate estimation */ && wallet.m_max_aps_fee > -1 && !coin_control.m_avoid_partial_spends) {
+    if (txr_ungrouped.fee > 0 /* 0 means non-functional fee rate estimation */ && wallet.m_max_aps_fee > -1 && !coin_control.m_avoid_partial_spends) {
         TRACE1(coin_selection, attempting_aps_create_tx, wallet.GetName().c_str());
         CCoinControl tmp_cc = coin_control;
         tmp_cc.m_avoid_partial_spends = true;
-        bilingual_str error2; // fired and forgotten; if an error occurs, we discard the results
-        std::optional<CreatedTransactionResult> txr_grouped = CreateTransactionInternal(wallet, vecSend, change_pos, error2, tmp_cc, fee_calc_out, sign);
+        auto res_tx_grouped = CreateTransactionInternal(wallet, vecSend, change_pos, tmp_cc, sign);
+        // Helper optional class for now
+        std::optional<CreatedTransactionResult> txr_grouped{res_tx_grouped.HasRes() ? std::make_optional(res_tx_grouped.GetObj()) : std::nullopt};
         // if fee of this alternative one is within the range of the max fee, we use this one
-        const bool use_aps{txr_grouped.has_value() ? (txr_grouped->fee <= txr_ungrouped->fee + wallet.m_max_aps_fee) : false};
+        const bool use_aps{txr_grouped.has_value() ? (txr_grouped->fee <= txr_ungrouped.fee + wallet.m_max_aps_fee) : false};
         TRACE5(coin_selection, aps_create_tx_internal, wallet.GetName().c_str(), use_aps, txr_grouped.has_value(),
                txr_grouped.has_value() ? txr_grouped->fee : 0, txr_grouped.has_value() ? txr_grouped->change_pos : 0);
         if (txr_grouped) {
             wallet.WalletLogPrintf("Fee non-grouped = %lld, grouped = %lld, using %s\n",
-                txr_ungrouped->fee, txr_grouped->fee, use_aps ? "grouped" : "non-grouped");
-            if (use_aps) return txr_grouped;
+                txr_ungrouped.fee, txr_grouped->fee, use_aps ? "grouped" : "non-grouped");
+            if (use_aps) return res_tx_grouped;
         }
     }
-    return txr_ungrouped;
+    return res;
 }
 
 bool FundTransaction(CWallet& wallet, CMutableTransaction& tx, CAmount& nFeeRet, int& nChangePosInOut, bilingual_str& error, bool lockUnspents, const std::set<int>& setSubtractFeeFromOutputs, CCoinControl coinControl)
@@ -1041,12 +1023,15 @@ bool FundTransaction(CWallet& wallet, CMutableTransaction& tx, CAmount& nFeeRet,
         }
     }
 
-    FeeCalculation fee_calc_out;
-    std::optional<CreatedTransactionResult> txr = CreateTransaction(wallet, vecSend, nChangePosInOut, error, coinControl, fee_calc_out, false);
-    if (!txr) return false;
-    CTransactionRef tx_new = txr->tx;
-    nFeeRet = txr->fee;
-    nChangePosInOut = txr->change_pos;
+    auto res = CreateTransaction(wallet, vecSend, nChangePosInOut, coinControl, false);
+    if (!res) {
+        error = res.GetError();
+        return false;
+    }
+    const auto& txr = res.GetObj();
+    CTransactionRef tx_new = txr.tx;
+    nFeeRet = txr.fee;
+    nChangePosInOut = txr.change_pos;
 
     if (nChangePosInOut != -1) {
         tx.vout.insert(tx.vout.begin() + nChangePosInOut, tx_new->vout[nChangePosInOut]);
diff --git a/src/wallet/spend.h b/src/wallet/spend.h
index 21f0095e77..ab0ff1ee58 100644
--- a/src/wallet/spend.h
+++ b/src/wallet/spend.h
@@ -6,6 +6,8 @@
 #define BITCOIN_WALLET_SPEND_H
 
 #include <consensus/amount.h>
+#include <policy/fees.h> // for FeeCalculation
+#include <util/result.h>
 #include <wallet/coinselection.h>
 #include <wallet/transaction.h>
 #include <wallet/wallet.h>
@@ -100,10 +102,11 @@ struct CreatedTransactionResult
 {
     CTransactionRef tx;
     CAmount fee;
+    FeeCalculation fee_calc;
     int change_pos;
 
-    CreatedTransactionResult(CTransactionRef tx, CAmount fee, int change_pos)
-        : tx(tx), fee(fee), change_pos(change_pos) {}
+    CreatedTransactionResult(CTransactionRef _tx, CAmount _fee, int _change_pos, const FeeCalculation& _fee_calc)
+        : tx(_tx), fee(_fee), fee_calc(_fee_calc), change_pos(_change_pos) {}
 };
 
 /**
@@ -111,7 +114,7 @@ struct CreatedTransactionResult
  * selected by SelectCoins(); Also create the change output, when needed
  * @note passing change_pos as -1 will result in setting a random position
  */
-std::optional<CreatedTransactionResult> CreateTransaction(CWallet& wallet, const std::vector<CRecipient>& vecSend, int change_pos, bilingual_str& error, const CCoinControl& coin_control, FeeCalculation& fee_calc_out, bool sign = true);
+BResult<CreatedTransactionResult> CreateTransaction(CWallet& wallet, const std::vector<CRecipient>& vecSend, int change_pos, const CCoinControl& coin_control, bool sign = true);
 
 /**
  * Insert additional inputs into the transaction by
diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp
index 9dd17c8e48..a418105ee1 100644
--- a/src/wallet/test/coinselector_tests.cpp
+++ b/src/wallet/test/coinselector_tests.cpp
@@ -74,11 +74,9 @@ static void add_coin(std::vector<COutput>& coins, CWallet& wallet, const CAmount
     tx.vout.resize(nInput + 1);
     tx.vout[nInput].nValue = nValue;
     if (spendable) {
-        CTxDestination dest;
-        bilingual_str error;
-        const bool destination_ok = wallet.GetNewDestination(OutputType::BECH32, "", dest, error);
-        assert(destination_ok);
-        tx.vout[nInput].scriptPubKey = GetScriptForDestination(dest);
+        auto op_dest = wallet.GetNewDestination(OutputType::BECH32, "");
+        assert(op_dest.HasRes());
+        tx.vout[nInput].scriptPubKey = GetScriptForDestination(op_dest.GetObj());
     }
     uint256 txid = tx.GetHash();
 
diff --git a/src/wallet/test/fuzz/notifications.cpp b/src/wallet/test/fuzz/notifications.cpp
index 9089c8ff46..816bef6148 100644
--- a/src/wallet/test/fuzz/notifications.cpp
+++ b/src/wallet/test/fuzz/notifications.cpp
@@ -69,15 +69,14 @@ struct FuzzedWallet {
     CScript GetScriptPubKey(FuzzedDataProvider& fuzzed_data_provider)
     {
         auto type{fuzzed_data_provider.PickValueInArray(OUTPUT_TYPES)};
-        CTxDestination dest;
-        bilingual_str error;
+        BResult<CTxDestination> op_dest;
         if (fuzzed_data_provider.ConsumeBool()) {
-            assert(wallet->GetNewDestination(type, "", dest, error));
+            op_dest = wallet->GetNewDestination(type, "");
         } else {
-            assert(wallet->GetNewChangeDestination(type, dest, error));
+            op_dest = wallet->GetNewChangeDestination(type);
         }
-        assert(error.empty());
-        return GetScriptForDestination(dest);
+        assert(op_dest.HasRes());
+        return GetScriptForDestination(op_dest.GetObj());
     }
 };
 
diff --git a/src/wallet/test/spend_tests.cpp b/src/wallet/test/spend_tests.cpp
index bdc148afb4..53c3b5d2ae 100644
--- a/src/wallet/test/spend_tests.cpp
+++ b/src/wallet/test/spend_tests.cpp
@@ -28,19 +28,18 @@ BOOST_FIXTURE_TEST_CASE(SubtractFee, TestChain100Setup)
     auto check_tx = [&wallet](CAmount leftover_input_amount) {
         CRecipient recipient{GetScriptForRawPubKey({}), 50 * COIN - leftover_input_amount, true /* subtract fee */};
         constexpr int RANDOM_CHANGE_POSITION = -1;
-        bilingual_str error;
         CCoinControl coin_control;
         coin_control.m_feerate.emplace(10000);
         coin_control.fOverrideFeeRate = true;
         // We need to use a change type with high cost of change so that the leftover amount will be dropped to fee instead of added as a change output
         coin_control.m_change_type = OutputType::LEGACY;
-        FeeCalculation fee_calc;
-        std::optional<CreatedTransactionResult> txr = CreateTransaction(*wallet, {recipient}, RANDOM_CHANGE_POSITION, error, coin_control, fee_calc);
-        BOOST_CHECK(txr.has_value());
-        BOOST_CHECK_EQUAL(txr->tx->vout.size(), 1);
-        BOOST_CHECK_EQUAL(txr->tx->vout[0].nValue, recipient.nAmount + leftover_input_amount - txr->fee);
-        BOOST_CHECK_GT(txr->fee, 0);
-        return txr->fee;
+        auto res = CreateTransaction(*wallet, {recipient}, RANDOM_CHANGE_POSITION, coin_control);
+        BOOST_CHECK(res);
+        const auto& txr = res.GetObj();
+        BOOST_CHECK_EQUAL(txr.tx->vout.size(), 1);
+        BOOST_CHECK_EQUAL(txr.tx->vout[0].nValue, recipient.nAmount + leftover_input_amount - txr.fee);
+        BOOST_CHECK_GT(txr.fee, 0);
+        return txr.fee;
     };
 
     // Send full input amount to recipient, check that only nonzero fee is
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index 4093392ff9..81c01e5023 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -4,7 +4,6 @@
 
 #include <wallet/wallet.h>
 
-#include <any>
 #include <future>
 #include <memory>
 #include <stdint.h>
@@ -13,7 +12,6 @@
 #include <interfaces/chain.h>
 #include <key_io.h>
 #include <node/blockstorage.h>
-#include <node/context.h>
 #include <policy/policy.h>
 #include <rpc/server.h>
 #include <test/util/logging.h>
@@ -536,14 +534,12 @@ public:
     CWalletTx& AddTx(CRecipient recipient)
     {
         CTransactionRef tx;
-        bilingual_str error;
         CCoinControl dummy;
-        FeeCalculation fee_calc_out;
         {
             constexpr int RANDOM_CHANGE_POSITION = -1;
-            std::optional<CreatedTransactionResult> txr = CreateTransaction(*wallet, {recipient}, RANDOM_CHANGE_POSITION, error, dummy, fee_calc_out);
-            BOOST_CHECK(txr.has_value());
-            tx = txr->tx;
+            auto res = CreateTransaction(*wallet, {recipient}, RANDOM_CHANGE_POSITION, dummy);
+            BOOST_CHECK(res);
+            tx = res.GetObj().tx;
         }
         wallet->CommitTransaction(tx, {}, {});
         CMutableTransaction blocktx;
@@ -629,9 +625,7 @@ BOOST_FIXTURE_TEST_CASE(wallet_disableprivkeys, TestChain100Setup)
         wallet->SetMinVersion(FEATURE_LATEST);
         wallet->SetWalletFlag(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
         BOOST_CHECK(!wallet->TopUpKeyPool(1000));
-        CTxDestination dest;
-        bilingual_str error;
-        BOOST_CHECK(!wallet->GetNewDestination(OutputType::BECH32, "", dest, error));
+        BOOST_CHECK(!wallet->GetNewDestination(OutputType::BECH32, ""));
     }
     {
         const std::shared_ptr<CWallet> wallet = std::make_shared<CWallet>(m_node.chain.get(), "", m_args, CreateDummyWalletDatabase());
@@ -639,9 +633,7 @@ BOOST_FIXTURE_TEST_CASE(wallet_disableprivkeys, TestChain100Setup)
         wallet->SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
         wallet->SetMinVersion(FEATURE_LATEST);
         wallet->SetWalletFlag(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
-        CTxDestination dest;
-        bilingual_str error;
-        BOOST_CHECK(!wallet->GetNewDestination(OutputType::BECH32, "", dest, error));
+        BOOST_CHECK(!wallet->GetNewDestination(OutputType::BECH32, ""));
     }
 }
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 79ec29f19a..de4a8a6eb7 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2318,37 +2318,36 @@ bool CWallet::TopUpKeyPool(unsigned int kpSize)
     return res;
 }
 
-bool CWallet::GetNewDestination(const OutputType type, const std::string label, CTxDestination& dest, bilingual_str& error)
+BResult<CTxDestination> CWallet::GetNewDestination(const OutputType type, const std::string label)
 {
     LOCK(cs_wallet);
-    error.clear();
-    bool result = false;
     auto spk_man = GetScriptPubKeyMan(type, false /* internal */);
-    if (spk_man) {
-        spk_man->TopUp();
-        result = spk_man->GetNewDestination(type, dest, error);
-    } else {
-        error = strprintf(_("Error: No %s addresses available."), FormatOutputType(type));
+    if (!spk_man) {
+        return strprintf(_("Error: No %s addresses available."), FormatOutputType(type));
     }
-    if (result) {
-        SetAddressBook(dest, label, "receive");
+
+    spk_man->TopUp();
+    auto op_dest = spk_man->GetNewDestination(type);
+    if (op_dest) {
+        SetAddressBook(op_dest.GetObj(), label, "receive");
     }
 
-    return result;
+    return op_dest;
 }
 
-bool CWallet::GetNewChangeDestination(const OutputType type, CTxDestination& dest, bilingual_str& error)
+BResult<CTxDestination> CWallet::GetNewChangeDestination(const OutputType type)
 {
     LOCK(cs_wallet);
-    error.clear();
 
+    CTxDestination dest;
+    bilingual_str error;
     ReserveDestination reservedest(this, type);
     if (!reservedest.GetReservedDestination(dest, true, error)) {
-        return false;
+        return error;
     }
 
     reservedest.KeepDestination();
-    return true;
+    return dest;
 }
 
 std::optional<int64_t> CWallet::GetOldestKeyPoolTime() const
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 865ce92311..e2c3d76438 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -15,6 +15,7 @@
 #include <psbt.h>
 #include <tinyformat.h>
 #include <util/message.h>
+#include <util/result.h>
 #include <util/strencodings.h>
 #include <util/string.h>
 #include <util/system.h>
@@ -45,7 +46,6 @@ using LoadWalletFn = std::function<void(std::unique_ptr<interfaces::Wallet> wall
 
 class CScript;
 enum class FeeEstimateMode;
-struct FeeCalculation;
 struct bilingual_str;
 
 namespace wallet {
@@ -666,8 +666,8 @@ public:
      */
     void MarkDestinationsDirty(const std::set<CTxDestination>& destinations) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
-    bool GetNewDestination(const OutputType type, const std::string label, CTxDestination& dest, bilingual_str& error);
-    bool GetNewChangeDestination(const OutputType type, CTxDestination& dest, bilingual_str& error);
+    BResult<CTxDestination> GetNewDestination(const OutputType type, const std::string label);
+    BResult<CTxDestination> GetNewChangeDestination(const OutputType type);
 
     isminetype IsMine(const CTxDestination& dest) const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     isminetype IsMine(const CScript& script) const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);