rpc: bumpfee, improve doc for 'reduce_output' arg

The current argument name and description are dangerous as it don't
describe the case where the user selects the recipient output as the
change address. This one could end up been increased by the inputs
minus outputs remainder. Which, when bumpfee adds new inputs
to the transaction, leads the process to send more coins to the
recipient. Which is not what the user would expect from a
'reduce_output' param naming.

Co-authored-by: Murch <murch@murch.one>

1 files changed, 12 insertions, 12 deletions

diff --git a/test/functional/wallet_bumpfee.py b/test/functional/wallet_bumpfee.py
index c66f279e88..fea933a93b 100755
--- a/test/functional/wallet_bumpfee.py
+++ b/test/functional/wallet_bumpfee.py
@@ -178,12 +178,12 @@ class BumpFeeTest(BitcoinTestFramework):
         assert_raises_rpc_error(-8, "Invalid parameter, duplicate key: data",
                 rbf_node.bumpfee, rbfid, {"outputs": [{"data": "deadbeef"}, {"data": "deadbeef"}]})
 
-        self.log.info("Test reduce_output option")
-        assert_raises_rpc_error(-1, "JSON integer out of range", rbf_node.bumpfee, rbfid, {"reduce_output": -1})
-        assert_raises_rpc_error(-8, "Change position is out of range", rbf_node.bumpfee, rbfid, {"reduce_output": 2})
+        self.log.info("Test original_change_index option")
+        assert_raises_rpc_error(-1, "JSON integer out of range", rbf_node.bumpfee, rbfid, {"original_change_index": -1})
+        assert_raises_rpc_error(-8, "Change position is out of range", rbf_node.bumpfee, rbfid, {"original_change_index": 2})
 
-        self.log.info("Test outputs and reduce_output cannot both be provided")
-        assert_raises_rpc_error(-8, "Cannot specify both new outputs to use and an output index to reduce", rbf_node.bumpfee, rbfid, {"reduce_output": 2, "outputs": [{dest_address: 0.1}]})
+        self.log.info("Test outputs and original_change_index cannot both be provided")
+        assert_raises_rpc_error(-8, "The options 'outputs' and 'original_change_index' are incompatible. You can only either specify a new set of outputs, or designate a change output to be recycled.", rbf_node.bumpfee, rbfid, {"original_change_index": 2, "outputs": [{dest_address: 0.1}]})
 
         self.clear_mempool()
 
@@ -237,7 +237,7 @@ class BumpFeeTest(BitcoinTestFramework):
         node.unloadwallet("back_to_yourself")
 
     def test_provided_change_pos(self, rbf_node):
-        self.log.info("Test the reduce_output option")
+        self.log.info("Test the original_change_index option")
 
         change_addr = rbf_node.getnewaddress()
         dest_addr = rbf_node.getnewaddress()
@@ -254,7 +254,7 @@ class BumpFeeTest(BitcoinTestFramework):
         change_pos = find_vout_for_address(rbf_node, txid, change_addr)
         change_value = tx["decoded"]["vout"][change_pos]["value"]
 
-        bumped = rbf_node.bumpfee(txid, {"reduce_output": change_pos})
+        bumped = rbf_node.bumpfee(txid, {"original_change_index": change_pos})
         new_txid = bumped["txid"]
 
         new_tx = rbf_node.gettransaction(txid=new_txid, verbose=True)
@@ -282,18 +282,18 @@ class BumpFeeTest(BitcoinTestFramework):
 
         tx = wallet.sendall(recipients=[wallet.getnewaddress()], fee_rate=2, options={"inputs": [utxos[0]]})
 
-        # Reduce the only output with a crazy high feerate, should fail as the output would be dust
-        assert_raises_rpc_error(-4, "The transaction amount is too small to pay the fee", wallet.bumpfee, txid=tx["txid"], options={"fee_rate": 1100, "reduce_output": 0})
+        # Set the only output with a crazy high feerate as change, should fail as the output would be dust
+        assert_raises_rpc_error(-4, "The transaction amount is too small to pay the fee", wallet.bumpfee, txid=tx["txid"], options={"fee_rate": 1100, "original_change_index": 0})
 
-        # Reduce the only output successfully
-        bumped = wallet.bumpfee(txid=tx["txid"], options={"fee_rate": 10, "reduce_output": 0})
+        # Specify single output as change successfully
+        bumped = wallet.bumpfee(txid=tx["txid"], options={"fee_rate": 10, "original_change_index": 0})
         bumped_tx = wallet.gettransaction(txid=bumped["txid"], verbose=True)
         assert_equal(len(bumped_tx["decoded"]["vout"]), 1)
         assert_equal(len(bumped_tx["decoded"]["vin"]), 1)
         assert_equal(bumped_tx["decoded"]["vout"][0]["value"] + bumped["fee"], amount)
         assert_fee_amount(bumped["fee"], bumped_tx["decoded"]["vsize"], Decimal(10) / Decimal(1e8) * 1000)
 
-        # Bumping without reducing adds a new input and output
+        # Bumping without specifying change adds a new input and output
         bumped = wallet.bumpfee(txid=bumped["txid"], options={"fee_rate": 20})
         bumped_tx = wallet.gettransaction(txid=bumped["txid"], verbose=True)
         assert_equal(len(bumped_tx["decoded"]["vout"]), 2)