rpc: creates possibility to preserve labels on importprivkey

- changes importprivkey behavior to overwrite existent label if one
is passed and keep existing ones if no label is passed

- tests behavior of importprivkey on existing address labels and
different same key destination

test/functional/wallet_import_with_label.py

@@ -0,0 +1,134 @@
+#!/usr/bin/env python3
+# Copyright (c) 2018 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 the behavior of RPC importprivkey on set and unset labels of
+addresses.
+
+It tests different cases in which an address is imported with importaddress
+with or without a label and then its private key is imported with importprivkey
+with and without a label.
+"""
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+
+class ImportWithLabel(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 2
+        self.setup_clean_chain = True
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_no_wallet()
+
+    def run_test(self):
+        """Main test logic"""
+
+        self.log.info(
+            "Test importaddress with label and importprivkey without label."
+        )
+        self.log.info("Import a watch-only address with a label.")
+        address = self.nodes[0].getnewaddress()
+        label = "Test Label"
+        self.nodes[1].importaddress(address, label)
+        address_assert = self.nodes[1].getaddressinfo(address)
+
+        assert_equal(address_assert["iswatchonly"], True)
+        assert_equal(address_assert["ismine"], False)
+        assert_equal(address_assert["label"], label)
+
+        self.log.info(
+            "Import the watch-only address's private key without a "
+            "label and the address should keep its label."
+        )
+        priv_key = self.nodes[0].dumpprivkey(address)
+        self.nodes[1].importprivkey(priv_key)
+
+        assert_equal(label, self.nodes[1].getaddressinfo(address)["label"])
+
+        self.log.info(
+            "Test importaddress without label and importprivkey with label."
+        )
+        self.log.info("Import a watch-only address without a label.")
+        address2 = self.nodes[0].getnewaddress()
+        self.nodes[1].importaddress(address2)
+        address_assert2 = self.nodes[1].getaddressinfo(address2)
+
+        assert_equal(address_assert2["iswatchonly"], True)
+        assert_equal(address_assert2["ismine"], False)
+        assert_equal(address_assert2["label"], "")
+
+        self.log.info(
+            "Import the watch-only address's private key with a "
+            "label and the address should have its label updated."
+        )
+        priv_key2 = self.nodes[0].dumpprivkey(address2)
+        label2 = "Test Label 2"
+        self.nodes[1].importprivkey(priv_key2, label2)
+
+        assert_equal(label2, self.nodes[1].getaddressinfo(address2)["label"])
+
+        self.log.info("Test importaddress with label and importprivkey with label.")
+        self.log.info("Import a watch-only address with a label.")
+        address3 = self.nodes[0].getnewaddress()
+        label3_addr = "Test Label 3 for importaddress"
+        self.nodes[1].importaddress(address3, label3_addr)
+        address_assert3 = self.nodes[1].getaddressinfo(address3)
+
+        assert_equal(address_assert3["iswatchonly"], True)
+        assert_equal(address_assert3["ismine"], False)
+        assert_equal(address_assert3["label"], label3_addr)
+
+        self.log.info(
+            "Import the watch-only address's private key with a "
+            "label and the address should have its label updated."
+        )
+        priv_key3 = self.nodes[0].dumpprivkey(address3)
+        label3_priv = "Test Label 3 for importprivkey"
+        self.nodes[1].importprivkey(priv_key3, label3_priv)
+
+        assert_equal(label3_priv, self.nodes[1].getaddressinfo(address3)["label"])
+
+        self.log.info(
+            "Test importprivkey won't label new dests with the same "
+            "label as others labeled dests for the same key."
+        )
+        self.log.info("Import a watch-only legacy address with a label.")
+        address4 = self.nodes[0].getnewaddress()
+        label4_addr = "Test Label 4 for importaddress"
+        self.nodes[1].importaddress(address4, label4_addr)
+        address_assert4 = self.nodes[1].getaddressinfo(address4)
+
+        assert_equal(address_assert4["iswatchonly"], True)
+        assert_equal(address_assert4["ismine"], False)
+        assert_equal(address_assert4["label"], label4_addr)
+
+        self.log.info("Asserts address has no embedded field with dests.")
+
+        assert_equal(address_assert4.get("embedded"), None)
+
+        self.log.info(
+            "Import the watch-only address's private key without a "
+            "label and new destinations for the key should have an "
+            "empty label while the 'old' destination should keep "
+            "its label."
+        )
+        priv_key4 = self.nodes[0].dumpprivkey(address4)
+        self.nodes[1].importprivkey(priv_key4)
+        address_assert4 = self.nodes[1].getaddressinfo(address4)
+
+        assert address_assert4.get("embedded")
+
+        bcaddress_assert = self.nodes[1].getaddressinfo(
+            address_assert4["embedded"]["address"]
+        )
+
+        assert_equal(address_assert4["label"], label4_addr)
+        assert_equal(bcaddress_assert["label"], "")
+
+        self.stop_nodes()
+
+
+if __name__ == "__main__":
+    ImportWithLabel().main()