Merge #18546: Bugfix: Wallet: Safely deal with change in the address book [part 2]

7a2ecf16df Wallet: Change IsMine check in CWallet::DelAddressBook from assert to failure (Luke Dashjr)
2952c46b92 Wallet: Replace CAddressBookData.name with GetLabel() method (Luke Dashjr)
d7092c392e QA: Test that change doesn't turn into non-change when spent in an avoid-reuse wallet (Luke Dashjr)

Pull request description:

  Follow-up to #18192, not strictly necessary for 0.20

ACKs for top commit:
  MarcoFalke:
    re-ACK 7a2ecf16df, only change is adding an assert_equal in the test 🔰
  jnewbery:
    utACK 7a2ecf16df

Tree-SHA512: e0933ee40f705b751697dc27249e1868ed4874254b174ebdd0a7150125d8c818402e66df2371718c7eeb90e67ee2317215fb260aa9b9d7b9b45ee436de2988ff

test/functional/wallet_avoidreuse.py

@@ -83,6 +83,7 @@ class AvoidReuseTest(BitcoinTestFramework):
 
         self.nodes[0].generate(110)
         self.sync_all()
+        self.test_change_remains_change(self.nodes[1])
         reset_balance(self.nodes[1], self.nodes[0].getnewaddress())
         self.test_fund_send_fund_senddirty()
         reset_balance(self.nodes[1], self.nodes[0].getnewaddress())
@@ -137,6 +138,30 @@ class AvoidReuseTest(BitcoinTestFramework):
         # Unload temp wallet
         self.nodes[1].unloadwallet(tempwallet)
 
+    def test_change_remains_change(self, node):
+        self.log.info("Test that change doesn't turn into non-change when spent")
+
+        reset_balance(node, node.getnewaddress())
+        addr = node.getnewaddress()
+        txid = node.sendtoaddress(addr, 1)
+        out = node.listunspent(minconf=0, query_options={'minimumAmount': 2})
+        assert_equal(len(out), 1)
+        assert_equal(out[0]['txid'], txid)
+        changeaddr = out[0]['address']
+
+        # Make sure it's starting out as change as expected
+        assert node.getaddressinfo(changeaddr)['ischange']
+        for logical_tx in node.listtransactions():
+            assert logical_tx.get('address') != changeaddr
+
+        # Spend it
+        reset_balance(node, node.getnewaddress())
+
+        # It should still be change
+        assert node.getaddressinfo(changeaddr)['ischange']
+        for logical_tx in node.listtransactions():
+            assert logical_tx.get('address') != changeaddr
+
     def test_fund_send_fund_senddirty(self):
         '''
         Test the same as test_fund_send_fund_send, except send the 10 BTC with