[backport#16377 2/2][rpc] fundrawtransaction: add_inputs option to co…

…ntrol automatic input adding

Summary:
---

Backport of Core [[bitcoin/bitcoin#16377 | PR16377]]

Depends on D8659

Note: replaced a couple unused `i` for-loop variables in functional tests that the linter complained about with `_`'s

Test Plan:
  ninja all check check-functional

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D8660

doc/release-notes.md

@@ -17,4 +17,7 @@ that `-salvagewallet` did.
 The `walletcreatefundedpsbt` RPC call will now fail with `Insufficient funds`
 when inputs are manually selected but are not enough to cover the outputs and
 fee. Additional inputs can automatically be added through the new `add_inputs`
-option.
+option.
+
+The `fundrawtransaction` RPC now supports `add_inputs` option that when `false`
+prevents adding more inputs if necessary and consequently the RPC fails.

src/wallet/rpcwallet.cpp

@@ -3829,10 +3829,9 @@ static UniValue fundrawtransaction(const Config &config,
 
     RPCHelpMan{
         "fundrawtransaction",
-        "Add inputs to a transaction until it has enough in value to meet "
-        "its out value.\n"
-        "This will not modify existing inputs, and will add at most one change "
-        "output to the outputs.\n"
+        "If the transaction has no inputs, they will be automatically selected "
+        "to meet its out value.\n"
+        "It will add at most one change output to the outputs.\n"
         "No existing outputs will be modified unless "
         "\"subtractFeeFromOutputs\" is specified.\n"
         "Note that inputs which were signed may need to be resigned after "
@@ -3858,6 +3857,9 @@ static UniValue fundrawtransaction(const Config &config,
              "for backward compatibility: passing in a true instead of an "
              "object will result in {\"includeWatching\":true}",
              {
+                 {"add_inputs", RPCArg::Type::BOOL, /* default */ "true",
+                  "For a transaction with existing inputs, automatically "
+                  "include more if they are not enough."},
                  {"changeAddress", RPCArg::Type::STR,
                   /* default */ "pool address",
                   "The bitcoin address to receive the change"},
@@ -3935,6 +3937,9 @@ static UniValue fundrawtransaction(const Config &config,
     Amount fee;
     int change_position;
     CCoinControl coin_control;
+    // Automatically select (additional) coins. Can be overridden by
+    // options.add_inputs.
+    coin_control.m_add_inputs = true;
     FundTransaction(pwallet, tx, fee, change_position, request.params[1],
                     coin_control);
 

test/functional/rpc_fundrawtransaction.py

@@ -283,7 +283,15 @@ def test_coin_selection(self):
         assert_equal(utx['txid'], dec_tx['vin'][0]['txid'])
         assert_equal("00", dec_tx['vin'][0]['scriptSig']['hex'])
 
+        # Should fail without add_inputs:
+        assert_raises_rpc_error(-4,
+                                "Insufficient funds",
+                                self.nodes[2].fundrawtransaction,
+                                rawTx,
+                                {"add_inputs": False})
+        # add_inputs is enabled by default
         rawtxfund = self.nodes[2].fundrawtransaction(rawTx)
+
         dec_tx = self.nodes[2].decoderawtransaction(rawtxfund['hex'])
         totalOut = 0
         matchingOuts = 0
@@ -312,7 +320,15 @@ def test_two_vin(self):
         dec_tx = self.nodes[2].decoderawtransaction(rawTx)
         assert_equal(utx['txid'], dec_tx['vin'][0]['txid'])
 
-        rawtxfund = self.nodes[2].fundrawtransaction(rawTx)
+        # Should fail without add_inputs:
+        assert_raises_rpc_error(-4,
+                                "Insufficient funds",
+                                self.nodes[2].fundrawtransaction,
+                                rawTx,
+                                {"add_inputs": False})
+        rawtxfund = self.nodes[2].fundrawtransaction(
+            rawTx, {"add_inputs": True})
+
         dec_tx = self.nodes[2].decoderawtransaction(rawtxfund['hex'])
         totalOut = 0
         matchingOuts = 0
@@ -346,7 +362,15 @@ def test_two_vin_two_vout(self):
         dec_tx = self.nodes[2].decoderawtransaction(rawTx)
         assert_equal(utx['txid'], dec_tx['vin'][0]['txid'])
 
-        rawtxfund = self.nodes[2].fundrawtransaction(rawTx)
+        # Should fail without add_inputs:
+        assert_raises_rpc_error(-4,
+                                "Insufficient funds",
+                                self.nodes[2].fundrawtransaction,
+                                rawTx,
+                                {"add_inputs": False})
+        rawtxfund = self.nodes[2].fundrawtransaction(
+            rawTx, {"add_inputs": True})
+
         dec_tx = self.nodes[2].decoderawtransaction(rawtxfund['hex'])
         totalOut = 0
         matchingOuts = 0
@@ -565,7 +589,7 @@ def test_many_inputs_fee(self):
         self.nodes[1].generate(1)
         self.sync_all()
 
-        for i in range(0, 20):
+        for _ in range(0, 20):
             self.nodes[0].sendtoaddress(self.nodes[1].getnewaddress(), 0.01)
         self.nodes[0].generate(1)
         self.sync_all()
@@ -596,7 +620,7 @@ def test_many_inputs_send(self):
         self.nodes[1].generate(1)
         self.sync_all()
 
-        for i in range(0, 20):
+        for _ in range(0, 20):
             self.nodes[0].sendtoaddress(self.nodes[1].getnewaddress(), 0.01)
         self.nodes[0].generate(1)
         self.sync_all()