wallet: Replace SelectExternal with SetTxOut

Instead of having a separate CCoinControl::SelectExternal function, we
can use the normal CCoinControl::Select function and explicitly use
PreselectedInput::SetTxOut in the caller. The semantics of what an
external input is remains.

src/wallet/coincontrol.cpp

@@ -41,12 +41,6 @@ PreselectedInput& CCoinControl::Select(const COutPoint& outpoint)
 {
     return m_selected[outpoint];
 }
-
-void CCoinControl::SelectExternal(const COutPoint& outpoint, const CTxOut& txout)
-{
-    m_selected[outpoint].SetTxOut(txout);
-}
-
 void CCoinControl::UnSelect(const COutPoint& outpoint)
 {
     m_selected.erase(outpoint);

src/wallet/coincontrol.h

@@ -108,11 +108,6 @@ public:
      * The output will be included in the transaction even if it's not the most optimal choice.
      */
     PreselectedInput& Select(const COutPoint& outpoint);
-    /**
-     * Lock-in the given output as an external input for spending because it is not in the wallet.
-     * The output will be included in the transaction even if it's not the most optimal choice.
-     */
-    void SelectExternal(const COutPoint& outpoint, const CTxOut& txout);
     /**
      * Unselects the given output.
      */

src/wallet/feebumper.cpp

@@ -203,10 +203,9 @@ Result CreateRateBumpTransaction(CWallet& wallet, const uint256& txid, const CCo
             errors.push_back(Untranslated(strprintf("%s:%u is already spent", txin.prevout.hash.GetHex(), txin.prevout.n)));
             return Result::MISC_ERROR;
         }
-        if (wallet.IsMine(txin.prevout)) {
-            new_coin_control.Select(txin.prevout);
-        } else {
-            new_coin_control.SelectExternal(txin.prevout, coin.out);
+        PreselectedInput& preset_txin = new_coin_control.Select(txin.prevout);
+        if (!wallet.IsMine(txin.prevout)) {
+            preset_txin.SetTxOut(coin.out);
         }
         input_value += coin.out.nValue;
         spent_outputs.push_back(coin.out);

src/wallet/spend.cpp

@@ -1347,15 +1347,15 @@ bool FundTransaction(CWallet& wallet, CMutableTransaction& tx, CAmount& nFeeRet,
 
     for (const CTxIn& txin : tx.vin) {
         const auto& outPoint = txin.prevout;
-        if (wallet.IsMine(outPoint)) {
-            // The input was found in the wallet, so select as internal
-            coinControl.Select(outPoint);
-        } else if (coins[outPoint].out.IsNull()) {
-            error = _("Unable to find UTXO for external input");
-            return false;
-        } else {
+        PreselectedInput& preset_txin = coinControl.Select(outPoint);
+        if (!wallet.IsMine(outPoint)) {
+            if (coins[outPoint].out.IsNull()) {
+                error = _("Unable to find UTXO for external input");
+                return false;
+            }
+
             // The input was not in the wallet, but is in the UTXO set, so select as external
-            coinControl.SelectExternal(outPoint, coins[outPoint].out);
+            preset_txin.SetTxOut(coins[outPoint].out);
         }
     }
 

src/wallet/test/coinselector_tests.cpp

@@ -1282,7 +1282,7 @@ BOOST_AUTO_TEST_CASE(SelectCoins_effective_value_test)
     cc.m_allow_other_inputs = false;
     COutput output = available_coins.All().at(0);
     cc.SetInputWeight(output.outpoint, 148);
-    cc.SelectExternal(output.outpoint, output.txout);
+    cc.Select(output.outpoint).SetTxOut(output.txout);
 
     LOCK(wallet->cs_wallet);
     const auto preset_inputs = *Assert(FetchSelectedInputs(*wallet, cc, cs_params));

src/wallet/test/fuzz/coincontrol.cpp

@@ -60,7 +60,7 @@ FUZZ_TARGET(coincontrol, .init = initialize_coincontrol)
             },
             [&] {
                 const CTxOut tx_out{ConsumeMoney(fuzzed_data_provider), ConsumeScript(fuzzed_data_provider)};
-                (void)coin_control.SelectExternal(out_point, tx_out);
+                (void)coin_control.Select(out_point).SetTxOut(tx_out);
             },
             [&] {
                 (void)coin_control.UnSelect(out_point);