[test] rescan legacy 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.

Author: glozow

test/functional/wallet_import_rescan.py

@@ -20,7 +20,10 @@
 """
 
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.address import AddressType
+from test_framework.address import (
+    AddressType,
+    ADDRESS_BCRT1_UNSPENDABLE,
+)
 from test_framework.util import (
     assert_equal,
     set_node_times,
@@ -109,7 +112,7 @@ def check(self, txid=None, amount=None, confirmation_height=None):
 
             address, = [ad for ad in addresses if txid in ad["txids"]]
             assert_equal(address["address"], self.address["address"])
-            assert_equal(address["amount"], self.expected_balance)
+            assert_equal(address["amount"], self.amount_received)
             assert_equal(address["confirmations"], confirmations)
             # Verify the transaction is correctly marked watchonly depending on
             # whether the transaction pays to an imported public key or
@@ -223,11 +226,11 @@ def run_test(self):
             variant.node = self.nodes[2 + IMPORT_NODES.index(ImportNode(variant.prune, expect_rescan))]
             variant.do_import(variant.timestamp)
             if expect_rescan:
-                variant.expected_balance = variant.initial_amount
+                variant.amount_received = variant.initial_amount
                 variant.expected_txs = 1
                 variant.check(variant.initial_txid, variant.initial_amount, variant.confirmation_height)
             else:
-                variant.expected_balance = 0
+                variant.amount_received = 0
                 variant.expected_txs = 0
                 variant.check()
 
@@ -247,7 +250,7 @@ def run_test(self):
         # Check the latest results from getbalance and listtransactions.
         for variant in IMPORT_VARIANTS:
             self.log.info('Run check for variant {}'.format(variant))
-            variant.expected_balance += variant.sent_amount
+            variant.amount_received += variant.sent_amount
             variant.expected_txs += 1
             variant.check(variant.sent_txid, variant.sent_amount, variant.confirmation_height)
 
@@ -267,14 +270,45 @@ def run_test(self):
                 address_type=variant.address_type.value,
             ))
             variant.key = self.nodes[1].dumpprivkey(variant.address["address"])
-            variant.initial_amount = get_rand_amount()
+            variant.initial_amount = get_rand_amount() * 2
             variant.initial_txid = self.nodes[0].sendtoaddress(variant.address["address"], variant.initial_amount)
             variant.confirmation_height = 0
             variant.timestamp = timestamp
 
+        # Mine a block so these parents are confirmed
+        assert_equal(len(self.nodes[0].getrawmempool()), len(mempool_variants))
+        self.sync_mempools()
+        block_to_disconnect = self.generate(self.nodes[0], 1)[0]
+        assert_equal(len(self.nodes[0].getrawmempool()), 0)
+
+        # For each variant, create an unconfirmed child transaction from initial_txid, 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.
+        # An equivalent test for descriptors exists in wallet_rescan_unconfirmed.py.
+        unspent_txid_map = {txin["txid"] : txin for txin in self.nodes[1].listunspent()}
+        for variant in mempool_variants:
+            # Send full amount, subtracting fee from outputs, to ensure no change is created.
+            child = self.nodes[1].send(
+                add_to_wallet=False,
+                inputs=[unspent_txid_map[variant.initial_txid]],
+                outputs=[{ADDRESS_BCRT1_UNSPENDABLE : variant.initial_amount}],
+                subtract_fee_from_outputs=[0]
+            )
+            variant.child_txid = child["txid"]
+            variant.amount_received = 0
+            self.nodes[0].sendrawtransaction(child["hex"])
+
+        # Mempools should contain the child transactions for each variant.
         assert_equal(len(self.nodes[0].getrawmempool()), len(mempool_variants))
         self.sync_mempools()
 
+        # Mock a reorg so the parent transactions are added back to the mempool
+        for node in self.nodes:
+            node.invalidateblock(block_to_disconnect)
+            # Mempools should now contain the parent and child for each variant.
+            assert_equal(len(node.getrawmempool()), 2 * len(mempool_variants))
+
         # For each variation of wallet key import, invoke the import RPC and
         # check the results from getbalance and listtransactions.
         for variant in mempool_variants:
@@ -283,11 +317,15 @@ def run_test(self):
             variant.node = self.nodes[2 + IMPORT_NODES.index(ImportNode(variant.prune, expect_rescan))]
             variant.do_import(variant.timestamp)
             if expect_rescan:
-                variant.expected_balance = variant.initial_amount
+                # Ensure both transactions were rescanned. This would raise a JSONRPCError if the
+                # transactions were not identified as belonging to the wallet.
+                assert_equal(variant.node.gettransaction(variant.initial_txid)['confirmations'], 0)
+                assert_equal(variant.node.gettransaction(variant.child_txid)['confirmations'], 0)
+                variant.amount_received = variant.initial_amount
                 variant.expected_txs = 1
-                variant.check(variant.initial_txid, variant.initial_amount)
+                variant.check(variant.initial_txid, variant.initial_amount, 0)
             else:
-                variant.expected_balance = 0
+                variant.amount_received = 0
                 variant.expected_txs = 0
                 variant.check()