Merge #18467: rpc: Improve documentation and return value of settxfee

38677274f931088218eeb1f258077d3387f39c89 rpc: settxfee respects -maxtxfee wallet setting (Fabian Jahr)
bda84a08a0ac92dff6cadc99cf9bb8c3fadd7e13 rpc: Add documentation for deactivating settxfee (Fabian Jahr)

Pull request description:

  ~~Closes 18315~~

  `settxfee` can be deactivated by passing 0 as the fee. That does not seem to be documented for the user so this PR adds it in the description. The return value of a simple boolean seems also too simplified given the multiple dimensions that this deactivation feature enables. I.e. it does not seem intuitive if the returned boolean shows that the call succeeded or if means that `settxfee` is active. My suggested solution is to change the return value to a JSON object that included the "active" state and the currently set fee rate.

  Examples:
  ```
  $ src/bitcoin-cli settxfee 0.0000000
  {
    "active": false,
    "fee_rate": "0.00000000 BTC/kB"
  }
  $ src/bitcoin-cli settxfee 0.0001
  {
    "active": true,
    "fee_rate": "0.00010000 BTC/kB"
  }
  ```

ACKs for top commit:
  MarcoFalke:
    ACK 38677274f931088218eeb1f258077d3387f39c89, seems useful to error out early instead of later #16257 🕍
  jonatack:
    ACK 38677274f931088218eeb
  meshcollider:
    LGTM, utACK 38677274f931088218eeb1f258077d3387f39c89

Tree-SHA512: 642813b5cf6612abb4b6cb63728081a6bd1659d809e0149c8f56060b6da7253fee989b3b202854f3051df3773c966799af30b612648c466b099f00590f356548

3 files changed, 16 insertions, 5 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index d24d92a178..ae3134b89a 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -2325,7 +2325,8 @@ static UniValue settxfee(const JSONRPCRequest& request)
     }
 
             RPCHelpMan{"settxfee",
-                "\nSet the transaction fee per kB for this wallet. Overrides the global -paytxfee command line parameter.\n",
+                "\nSet the transaction fee per kB for this wallet. Overrides the global -paytxfee command line parameter.\n"
+                "Can be deactivated by passing 0 as the fee. In that case automatic fee selection will be used by default.\n",
                 {
                     {"amount", RPCArg::Type::AMOUNT, RPCArg::Optional::NO, "The transaction fee in " + CURRENCY_UNIT + "/kB"},
                 },
@@ -2343,12 +2344,15 @@ static UniValue settxfee(const JSONRPCRequest& request)
 
     CAmount nAmount = AmountFromValue(request.params[0]);
     CFeeRate tx_fee_rate(nAmount, 1000);
+    CFeeRate max_tx_fee_rate(pwallet->m_default_max_tx_fee, 1000);
     if (tx_fee_rate == CFeeRate(0)) {
         // automatic selection
     } else if (tx_fee_rate < pwallet->chain().relayMinFee()) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than min relay tx fee (%s)", pwallet->chain().relayMinFee().ToString()));
     } else if (tx_fee_rate < pwallet->m_min_fee) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be less than wallet min fee (%s)", pwallet->m_min_fee.ToString()));
+    } else if (tx_fee_rate > max_tx_fee_rate) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("txfee cannot be more than wallet max tx fee (%s)", max_tx_fee_rate.ToString()));
     }
 
     pwallet->m_pay_tx_fee = tx_fee_rate;
diff --git a/test/functional/wallet_bumpfee.py b/test/functional/wallet_bumpfee.py
index 0b3dea94d5..17f7fdf916 100755
--- a/test/functional/wallet_bumpfee.py
+++ b/test/functional/wallet_bumpfee.py
@@ -82,7 +82,6 @@ class BumpFeeTest(BitcoinTestFramework):
         test_notmine_bumpfee_fails(self, rbf_node, peer_node, dest_address)
         test_bumpfee_with_descendant_fails(self, rbf_node, rbf_node_address, dest_address)
         test_dust_to_fee(self, rbf_node, dest_address)
-        test_settxfee(self, rbf_node, dest_address)
         test_watchonly_psbt(self, peer_node, rbf_node, dest_address)
         test_rebumping(self, rbf_node, dest_address)
         test_rebumping_not_replaceable(self, rbf_node, dest_address)
@@ -90,6 +89,7 @@ class BumpFeeTest(BitcoinTestFramework):
         test_bumpfee_metadata(self, rbf_node, dest_address)
         test_locked_wallet_fails(self, rbf_node, dest_address)
         test_change_script_match(self, rbf_node, dest_address)
+        test_settxfee(self, rbf_node, dest_address)
         test_maxtxfee_fails(self, rbf_node, dest_address)
         # These tests wipe out a number of utxos that are expected in other tests
         test_small_output_with_feerate_succeeds(self, rbf_node, dest_address)
@@ -286,9 +286,15 @@ def test_settxfee(self, rbf_node, dest_address):
     assert_greater_than(Decimal("0.00001000"), abs(requested_feerate - actual_feerate))
     rbf_node.settxfee(Decimal("0.00000000"))  # unset paytxfee
 
+    # check that settxfee respects -maxtxfee
+    self.restart_node(1, ['-maxtxfee=0.000025'] + self.extra_args[1])
+    assert_raises_rpc_error(-8, "txfee cannot be more than wallet max tx fee", rbf_node.settxfee, Decimal('0.00003'))
+    self.restart_node(1, self.extra_args[1])
+    rbf_node.walletpassphrase(WALLET_PASSPHRASE, WALLET_PASSPHRASE_TIMEOUT)
+
 
 def test_maxtxfee_fails(self, rbf_node, dest_address):
-    self.log.info('Test that bumpfee fails when it hits -matxfee')
+    self.log.info('Test that bumpfee fails when it hits -maxtxfee')
     # size of bumped transaction (p2wpkh, 1 input, 2 outputs): 141 vbytes
     # expected bump fee of 141 vbytes * 0.00200000 BTC / 1000 vbytes = 0.00002820 BTC
     # which exceeds maxtxfee and is expected to raise
diff --git a/test/functional/wallet_multiwallet.py b/test/functional/wallet_multiwallet.py
index a2c502f280..1fcf0e1dd7 100755
--- a/test/functional/wallet_multiwallet.py
+++ b/test/functional/wallet_multiwallet.py
@@ -6,6 +6,7 @@
 
 Verify that a bitcoind node can load multiple wallet files
 """
+from decimal import Decimal
 import os
 import shutil
 import time
@@ -193,9 +194,9 @@ class MultiWalletTest(BitcoinTestFramework):
         self.log.info('Check for per-wallet settxfee call')
         assert_equal(w1.getwalletinfo()['paytxfee'], 0)
         assert_equal(w2.getwalletinfo()['paytxfee'], 0)
-        w2.settxfee(4.0)
+        w2.settxfee(0.001)
         assert_equal(w1.getwalletinfo()['paytxfee'], 0)
-        assert_equal(w2.getwalletinfo()['paytxfee'], 4.0)
+        assert_equal(w2.getwalletinfo()['paytxfee'], Decimal('0.00100000'))
 
         self.log.info("Test dynamic wallet loading")