Merge #15557: Enhance bumpfee to include inputs when targeting a feerate

184f8785f wallet_bumpfee.py: add test for change key preservation (Gregory Sanders)
d08becff8 add functional tests for feerate bumpfee with adding inputs (Gregory Sanders)
0ea47ba7b generalize bumpfee to add inputs when needed (Gregory Sanders)

Pull request description:

  When targeting a feerate using `bumpfee`, call a new function that directly uses `CWallet::CreateTransaction` and coin control to get the desired result. This allows us to get a superset of previous behavior, with an arbitrary RBF bump of a transaction provided it passes the preconditional checks and spare confirmed utxos are available.

  Note(s):
  0) The coin selection will use knapsack solver for the residual selection.
  1) This functionality, just like knapsack coin selection in general, will hoover up negative-value inputs when given the chance.
  2) Newly added inputs must be confirmed due to current Core policy. See error: `replacement-adds-unconfirmed`
  3) Supporting this with `totalFee` is difficult since the "minimum total fee" option in `CreateTransaction` logic was (rightly)taken out in #10390 .

ACKs for commit 184f87:
  jnewbery:
    utACK 184f8785f7

Tree-SHA512: fb6542bdfb2c6010e328ec475cf9dcbff4eb2b1a1b27f78010214534908987a5635797196fa05edddffcbcf2987335872dc644a99261886d5cbb34a8f262ad3e

test/functional/wallet_bumpfee.py

@@ -79,6 +79,10 @@ class BumpFeeTest(BitcoinTestFramework):
         test_unconfirmed_not_spendable(rbf_node, rbf_node_address)
         test_bumpfee_metadata(rbf_node, dest_address)
         test_locked_wallet_fails(rbf_node, dest_address)
+        test_change_script_match(rbf_node, dest_address)
+        # These tests wipe out a number of utxos that are expected in other tests
+        test_small_output_with_feerate_succeeds(rbf_node, dest_address)
+        test_no_more_inputs_fails(rbf_node, dest_address)
         self.log.info("Success")
 
 
@@ -179,6 +183,40 @@ def test_small_output_fails(rbf_node, dest_address):
     rbfid = spend_one_input(rbf_node, dest_address)
     assert_raises_rpc_error(-4, "Change output is too small", rbf_node.bumpfee, rbfid, {"totalFee": 50001})
 
+def test_small_output_with_feerate_succeeds(rbf_node, dest_address):
+
+    # Make sure additional inputs exist
+    rbf_node.generatetoaddress(101, rbf_node.getnewaddress())
+    rbfid = spend_one_input(rbf_node, dest_address)
+    original_input_list = rbf_node.getrawtransaction(rbfid, 1)["vin"]
+    assert_equal(len(original_input_list), 1)
+    original_txin = original_input_list[0]
+    # Keep bumping until we out-spend change output
+    tx_fee = 0
+    while tx_fee < Decimal("0.0005"):
+        new_input_list = rbf_node.getrawtransaction(rbfid, 1)["vin"]
+        new_item = list(new_input_list)[0]
+        assert_equal(len(original_input_list), 1)
+        assert_equal(original_txin["txid"], new_item["txid"])
+        assert_equal(original_txin["vout"], new_item["vout"])
+        rbfid_new_details = rbf_node.bumpfee(rbfid)
+        rbfid_new = rbfid_new_details["txid"]
+        raw_pool = rbf_node.getrawmempool()
+        assert rbfid not in raw_pool
+        assert rbfid_new in raw_pool
+        rbfid = rbfid_new
+        tx_fee = rbfid_new_details["origfee"]
+
+    # input(s) have been added
+    final_input_list = rbf_node.getrawtransaction(rbfid, 1)["vin"]
+    assert_greater_than(len(final_input_list), 1)
+    # Original input is in final set
+    assert [txin for txin in final_input_list
+            if txin["txid"] == original_txin["txid"]
+            and txin["vout"] == original_txin["vout"]]
+
+    rbf_node.generatetoaddress(1, rbf_node.getnewaddress())
+    assert_equal(rbf_node.gettransaction(rbfid)["confirmations"], 1)
 
 def test_dust_to_fee(rbf_node, dest_address):
     # check that if output is reduced to dust, it will be converted to fee
@@ -278,19 +316,37 @@ def test_locked_wallet_fails(rbf_node, dest_address):
     rbf_node.walletlock()
     assert_raises_rpc_error(-13, "Please enter the wallet passphrase with walletpassphrase first.",
                             rbf_node.bumpfee, rbfid)
+    rbf_node.walletpassphrase(WALLET_PASSPHRASE, WALLET_PASSPHRASE_TIMEOUT)
 
+def test_change_script_match(rbf_node, dest_address):
+    """Test that the same change addresses is used for the replacement transaction when possible."""
+    def get_change_address(tx):
+        tx_details = rbf_node.getrawtransaction(tx, 1)
+        txout_addresses = [txout['scriptPubKey']['addresses'][0] for txout in tx_details["vout"]]
+        return [address for address in txout_addresses if rbf_node.getaddressinfo(address)["ischange"]]
 
-def spend_one_input(node, dest_address):
+    # Check that there is only one change output
+    rbfid = spend_one_input(rbf_node, dest_address)
+    change_addresses = get_change_address(rbfid)
+    assert_equal(len(change_addresses), 1)
+
+    # Now find that address in each subsequent tx, and no other change
+    bumped_total_tx = rbf_node.bumpfee(rbfid, {"totalFee": 2000})
+    assert_equal(change_addresses, get_change_address(bumped_total_tx['txid']))
+    bumped_rate_tx = rbf_node.bumpfee(bumped_total_tx["txid"])
+    assert_equal(change_addresses, get_change_address(bumped_rate_tx['txid']))
+
+def spend_one_input(node, dest_address, change_size=Decimal("0.00049000")):
     tx_input = dict(
         sequence=BIP125_SEQUENCE_NUMBER, **next(u for u in node.listunspent() if u["amount"] == Decimal("0.00100000")))
-    rawtx = node.createrawtransaction(
-        [tx_input], {dest_address: Decimal("0.00050000"),
-                     node.getrawchangeaddress(): Decimal("0.00049000")})
+    destinations = {dest_address: Decimal("0.00050000")}
+    if change_size > 0:
+        destinations[node.getrawchangeaddress()] = change_size
+    rawtx = node.createrawtransaction([tx_input], destinations)
     signedtx = node.signrawtransactionwithwallet(rawtx)
     txid = node.sendrawtransaction(signedtx["hex"])
     return txid
 
-
 def submit_block_with_tx(node, tx):
     ctx = CTransaction()
     ctx.deserialize(io.BytesIO(hex_str_to_bytes(tx)))
@@ -307,6 +363,12 @@ def submit_block_with_tx(node, tx):
     node.submitblock(block.serialize(True).hex())
     return block
 
+def test_no_more_inputs_fails(rbf_node, dest_address):
+    # feerate rbf requires confirmed outputs when change output doesn't exist or is insufficient
+    rbf_node.generatetoaddress(1, dest_address)
+    # spend all funds, no change output
+    rbfid = rbf_node.sendtoaddress(rbf_node.getnewaddress(), rbf_node.getbalance(), "", "", True)
+    assert_raises_rpc_error(-4, "Unable to create transaction: Insufficient funds", rbf_node.bumpfee, rbfid)
 
 if __name__ == "__main__":
     BumpFeeTest().main()