[test] import descriptor wallet with reorged parent + IsFromMe child in mempool

Test that wallet rescans process transactions topologically, even if a
parent's entry into the mempool is later than that of its child.
This behavior is important because IsFromMe requires the ability to look
up a transaction's inputs.

Co-authored-by: furszy <matiasfurszyfer@protonmail.com>

test/functional/test_runner.py

@@ -335,6 +335,7 @@ BASE_SCRIPTS = [
     'wallet_create_tx.py --descriptors',
     'wallet_inactive_hdchains.py --legacy-wallet',
     'wallet_spend_unconfirmed.py',
+    'wallet_rescan_unconfirmed.py --descriptors',
     'p2p_fingerprint.py',
     'feature_uacomment.py',
     'feature_init.py',

test/functional/wallet_rescan_unconfirmed.py

@@ -0,0 +1,83 @@
+#!/usr/bin/env python3
+# Copyright (c) 2024 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test that descriptor wallets rescan mempool transactions properly when importing."""
+
+from test_framework.address import (
+    address_to_scriptpubkey,
+    ADDRESS_BCRT1_UNSPENDABLE,
+)
+from test_framework.messages import COIN
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+from test_framework.wallet import MiniWallet
+from test_framework.wallet_util import test_address
+
+
+class WalletRescanUnconfirmed(BitcoinTestFramework):
+    def add_options(self, parser):
+        self.add_wallet_options(parser, legacy=False)
+
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_no_wallet()
+        self.skip_if_no_sqlite()
+
+    def run_test(self):
+        self.log.info("Create wallets and mine initial chain")
+        node = self.nodes[0]
+        tester_wallet = MiniWallet(node)
+
+        node.createwallet(wallet_name='w0', disable_private_keys=False)
+        w0 = node.get_wallet_rpc('w0')
+
+        self.log.info("Create a parent tx and mine it in a block that will later be disconnected")
+        parent_address = w0.getnewaddress()
+        tx_parent_to_reorg = tester_wallet.send_to(
+            from_node=node,
+            scriptPubKey=address_to_scriptpubkey(parent_address),
+            amount=COIN,
+        )
+        assert tx_parent_to_reorg["txid"] in node.getrawmempool()
+        block_to_reorg = self.generate(tester_wallet, 1)[0]
+        assert_equal(len(node.getrawmempool()), 0)
+        node.syncwithvalidationinterfacequeue()
+        assert_equal(w0.gettransaction(tx_parent_to_reorg["txid"])["confirmations"], 1)
+
+        # Create an unconfirmed child transaction from the parent tx, sending all
+        # the funds to an unspendable address. Importantly, no change output is created so the
+        # transaction can't be recognized using its outputs. The wallet rescan needs to know the
+        # inputs of the transaction to detect it, so the parent must be processed before the child.
+        w0_utxos = w0.listunspent()
+
+        self.log.info("Create a child tx and wait for it to propagate to all mempools")
+        # The only UTXO available to spend is tx_parent_to_reorg.
+        assert_equal(len(w0_utxos), 1)
+        assert_equal(w0_utxos[0]["txid"], tx_parent_to_reorg["txid"])
+        tx_child_unconfirmed_sweep = w0.sendall([ADDRESS_BCRT1_UNSPENDABLE])
+        assert tx_child_unconfirmed_sweep["txid"] in node.getrawmempool()
+        node.syncwithvalidationinterfacequeue()
+
+        self.log.info("Mock a reorg, causing parent to re-enter mempools after its child")
+        node.invalidateblock(block_to_reorg)
+        assert tx_parent_to_reorg["txid"] in node.getrawmempool()
+
+        self.log.info("Import descriptor wallet on another node")
+        descriptors_to_import = [{"desc": w0.getaddressinfo(parent_address)['parent_desc'], "timestamp": 0, "label": "w0 import"}]
+
+        node.createwallet(wallet_name="w1", disable_private_keys=True)
+        w1 = node.get_wallet_rpc("w1")
+        w1.importdescriptors(descriptors_to_import)
+
+        self.log.info("Check that the importing node has properly rescanned mempool transactions")
+        # Check that parent address is correctly determined as ismine
+        test_address(w1, parent_address, solvable=True, ismine=True)
+        # This would raise a JSONRPCError if the transactions were not identified as belonging to the wallet.
+        assert_equal(w1.gettransaction(tx_parent_to_reorg["txid"])["confirmations"], 0)
+        assert_equal(w1.gettransaction(tx_child_unconfirmed_sweep["txid"])["confirmations"], 0)
+
+if __name__ == '__main__':
+    WalletRescanUnconfirmed().main()