wallet: return 'CoinsResult' struct in `AvailableCoins`

Instead of accepting a `vCoins` reference that is cleared at the beginning of the method.

Note:
This new struct, down the commits line, will contain other `AvailableCoins` useful results.

5 files changed, 30 insertions, 32 deletions

diff --git a/src/wallet/rpc/coins.cpp b/src/wallet/rpc/coins.cpp
index 2649fa586c..5efb61c3bd 100644
--- a/src/wallet/rpc/coins.cpp
+++ b/src/wallet/rpc/coins.cpp
@@ -638,7 +638,7 @@ RPCHelpMan listunspent()
         cctl.m_max_depth = nMaxDepth;
         cctl.m_include_unsafe_inputs = include_unsafe;
         LOCK(pwallet->cs_wallet);
-        AvailableCoinsListUnspent(*pwallet, vecOutputs, &cctl, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount);
+        vecOutputs = AvailableCoinsListUnspent(*pwallet, &cctl, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount).coins;
     }
 
     LOCK(pwallet->cs_wallet);
diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index d1a0ba50f6..98e180e4a1 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/src/wallet/rpc/spend.cpp
@@ -1380,7 +1380,6 @@ RPCHelpMan sendall()
 
             CMutableTransaction rawTx{ConstructTransaction(options["inputs"], recipient_key_value_pairs, options["locktime"], rbf)};
             LOCK(pwallet->cs_wallet);
-            std::vector<COutput> all_the_utxos;
 
             CAmount total_input_value(0);
             bool send_max{options.exists("send_max") ? options["send_max"].get_bool() : false};
@@ -1398,8 +1397,7 @@ RPCHelpMan sendall()
                     total_input_value += tx->tx->vout[input.prevout.n].nValue;
                 }
             } else {
-                AvailableCoins(*pwallet, all_the_utxos, &coin_control, fee_rate, /*nMinimumAmount=*/0);
-                for (const COutput& output : all_the_utxos) {
+                for (const COutput& output : AvailableCoins(*pwallet, &coin_control, fee_rate, /*nMinimumAmount=*/0).coins) {
                     CHECK_NONFATAL(output.input_bytes > 0);
                     if (send_max && fee_rate.GetFee(output.input_bytes) > output.txout.nValue) {
                         continue;
diff --git a/src/wallet/spend.cpp b/src/wallet/spend.cpp
index fe36cfcc6b..79c8f064c0 100644
--- a/src/wallet/spend.cpp
+++ b/src/wallet/spend.cpp
@@ -84,11 +84,17 @@ TxSize CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *walle
     return CalculateMaximumSignedTxSize(tx, wallet, txouts, coin_control);
 }
 
-void AvailableCoins(const CWallet& wallet, std::vector<COutput>& vCoins, const CCoinControl* coinControl, std::optional<CFeeRate> feerate, const CAmount& nMinimumAmount, const CAmount& nMaximumAmount, const CAmount& nMinimumSumAmount, const uint64_t nMaximumCount)
+CoinsResult AvailableCoins(const CWallet& wallet,
+                           const CCoinControl* coinControl,
+                           std::optional<CFeeRate> feerate,
+                           const CAmount& nMinimumAmount,
+                           const CAmount& nMaximumAmount,
+                           const CAmount& nMinimumSumAmount,
+                           const uint64_t nMaximumCount)
 {
     AssertLockHeld(wallet.cs_wallet);
 
-    vCoins.clear();
+    CoinsResult result;
     CAmount nTotal = 0;
     // Either the WALLET_FLAG_AVOID_REUSE flag is not set (in which case we always allow), or we default to avoiding, and only in the case where
     // a coin control object is provided, and has the avoid address reuse flag set to false, do we allow already used addresses
@@ -191,29 +197,30 @@ void AvailableCoins(const CWallet& wallet, std::vector<COutput>& vCoins, const C
             bool solvable = provider ? IsSolvable(*provider, wtx.tx->vout[i].scriptPubKey) : false;
             bool spendable = ((mine & ISMINE_SPENDABLE) != ISMINE_NO) || (((mine & ISMINE_WATCH_ONLY) != ISMINE_NO) && (coinControl && coinControl->fAllowWatchOnly && solvable));
             int input_bytes = GetTxSpendSize(wallet, wtx, i, (coinControl && coinControl->fAllowWatchOnly));
-
-            vCoins.emplace_back(COutPoint(wtx.GetHash(), i), wtx.tx->vout.at(i), nDepth, input_bytes, spendable, solvable, safeTx, wtx.GetTxTime(), tx_from_me, feerate);
+            result.coins.emplace_back(COutPoint(wtx.GetHash(), i), wtx.tx->vout.at(i), nDepth, input_bytes, spendable, solvable, safeTx, wtx.GetTxTime(), tx_from_me, feerate);
 
             // Checks the sum amount of all UTXO's.
             if (nMinimumSumAmount != MAX_MONEY) {
                 nTotal += wtx.tx->vout[i].nValue;
 
                 if (nTotal >= nMinimumSumAmount) {
-                    return;
+                    return result;
                 }
             }
 
             // Checks the maximum number of UTXO's.
-            if (nMaximumCount > 0 && vCoins.size() >= nMaximumCount) {
-                return;
+            if (nMaximumCount > 0 && result.coins.size() >= nMaximumCount) {
+                return result;
             }
         }
     }
+
+    return result;
 }
 
-void AvailableCoinsListUnspent(const CWallet& wallet, std::vector<COutput>& vCoins, const CCoinControl* coinControl, const CAmount& nMinimumAmount, const CAmount& nMaximumAmount, const CAmount& nMinimumSumAmount, const uint64_t nMaximumCount)
+CoinsResult AvailableCoinsListUnspent(const CWallet& wallet, const CCoinControl* coinControl, const CAmount& nMinimumAmount, const CAmount& nMaximumAmount, const CAmount& nMinimumSumAmount, const uint64_t nMaximumCount)
 {
-    AvailableCoins(wallet, vCoins, coinControl, /*feerate=*/ std::nullopt, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount);
+    return AvailableCoins(wallet, coinControl, /*feerate=*/ std::nullopt, nMinimumAmount, nMaximumAmount, nMinimumSumAmount, nMaximumCount);
 }
 
 CAmount GetAvailableBalance(const CWallet& wallet, const CCoinControl* coinControl)
@@ -221,9 +228,7 @@ CAmount GetAvailableBalance(const CWallet& wallet, const CCoinControl* coinContr
     LOCK(wallet.cs_wallet);
 
     CAmount balance = 0;
-    std::vector<COutput> vCoins;
-    AvailableCoinsListUnspent(wallet, vCoins, coinControl);
-    for (const COutput& out : vCoins) {
+    for (const COutput& out : AvailableCoinsListUnspent(wallet, coinControl).coins) {
         if (out.spendable) {
             balance += out.txout.nValue;
         }
@@ -260,11 +265,8 @@ std::map<CTxDestination, std::vector<COutput>> ListCoins(const CWallet& wallet)
     AssertLockHeld(wallet.cs_wallet);
 
     std::map<CTxDestination, std::vector<COutput>> result;
-    std::vector<COutput> availableCoins;
-
-    AvailableCoinsListUnspent(wallet, availableCoins);
 
-    for (const COutput& coin : availableCoins) {
+    for (const COutput& coin : AvailableCoinsListUnspent(wallet).coins) {
         CTxDestination address;
         if ((coin.spendable || (wallet.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) && coin.solvable)) &&
             ExtractDestination(FindNonChangeParentOutput(wallet, coin.outpoint).scriptPubKey, address)) {
@@ -791,11 +793,10 @@ static std::optional<CreatedTransactionResult> CreateTransactionInternal(
     CAmount selection_target = recipients_sum + not_input_fees;
 
     // Get available coins
-    std::vector<COutput> vAvailableCoins;
-    AvailableCoins(wallet, vAvailableCoins, &coin_control, coin_selection_params.m_effective_feerate, 1, MAX_MONEY, MAX_MONEY, 0);
+    auto res_available_coins = AvailableCoins(wallet, &coin_control, coin_selection_params.m_effective_feerate, 1, MAX_MONEY, MAX_MONEY, 0);
 
     // Choose coins to use
-    std::optional<SelectionResult> result = SelectCoins(wallet, vAvailableCoins, /*nTargetValue=*/selection_target, coin_control, coin_selection_params);
+    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;
diff --git a/src/wallet/spend.h b/src/wallet/spend.h
index 988058a25a..dde2523eb7 100644
--- a/src/wallet/spend.h
+++ b/src/wallet/spend.h
@@ -34,16 +34,19 @@ struct TxSize {
 TxSize CalculateMaximumSignedTxSize(const CTransaction& tx, const CWallet* wallet, const std::vector<CTxOut>& txouts, const CCoinControl* coin_control = nullptr);
 TxSize CalculateMaximumSignedTxSize(const CTransaction& tx, const CWallet* wallet, const CCoinControl* coin_control = nullptr) EXCLUSIVE_LOCKS_REQUIRED(wallet->cs_wallet);
 
+struct CoinsResult {
+    std::vector<COutput> coins;
+};
 /**
- * populate vCoins with vector of available COutputs.
+ * Return vector of available COutputs.
  */
-void AvailableCoins(const CWallet& wallet, std::vector<COutput>& vCoins, const CCoinControl* coinControl = nullptr, std::optional<CFeeRate> feerate = std::nullopt, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t nMaximumCount = 0) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet);
+CoinsResult AvailableCoins(const CWallet& wallet, const CCoinControl* coinControl = nullptr, std::optional<CFeeRate> feerate = std::nullopt, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t nMaximumCount = 0) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet);
 
 /**
  * Wrapper function for AvailableCoins which skips the `feerate` parameter. Use this function
  * to list all available coins (e.g. listunspent RPC) while not intending to fund a transaction.
  */
-void AvailableCoinsListUnspent(const CWallet& wallet, std::vector<COutput>& vCoins, const CCoinControl* coinControl = nullptr, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t nMaximumCount = 0) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet);
+CoinsResult AvailableCoinsListUnspent(const CWallet& wallet, const CCoinControl* coinControl = nullptr, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t nMaximumCount = 0) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet);
 
 CAmount GetAvailableBalance(const CWallet& wallet, const CCoinControl* coinControl = nullptr);
 
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index 70863f5464..0c03b2f4a2 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -583,9 +583,7 @@ BOOST_FIXTURE_TEST_CASE(ListCoinsTest, ListCoinsTestingSetup)
     // Lock both coins. Confirm number of available coins drops to 0.
     {
         LOCK(wallet->cs_wallet);
-        std::vector<COutput> available;
-        AvailableCoinsListUnspent(*wallet, available);
-        BOOST_CHECK_EQUAL(available.size(), 2U);
+        BOOST_CHECK_EQUAL(AvailableCoinsListUnspent(*wallet).coins.size(), 2U);
     }
     for (const auto& group : list) {
         for (const auto& coin : group.second) {
@@ -595,9 +593,7 @@ BOOST_FIXTURE_TEST_CASE(ListCoinsTest, ListCoinsTestingSetup)
     }
     {
         LOCK(wallet->cs_wallet);
-        std::vector<COutput> available;
-        AvailableCoinsListUnspent(*wallet, available);
-        BOOST_CHECK_EQUAL(available.size(), 0U);
+        BOOST_CHECK_EQUAL(AvailableCoinsListUnspent(*wallet).coins.size(), 0U);
     }
     // Confirm ListCoins still returns same result as before, despite coins
     // being locked.