Merge bitcoin#18855: tests: feature_backwards_compatibility.py test downgrade after upgrade

489ebfd tests: feature_backwards_compatibility.py test downgrade after upgrade (Andrew Chow)

Pull request description:

  After upgrading the node, try to go back to the original version to make sure that using a newer node version does not prevent the wallet file from being downgraded again.

ACKs for top commit:
  MarcoFalke:
    ACK 489ebfd

Tree-SHA512: 86231de6514b3657912fd9d6621212166fd2b29b591fc97120092c548babcf1d6f50b5bd103b28cecde395a26809134f01c1a198725596c3626420de3fd1f017

Author: MarcoFalke

test/functional/feature_backwards_compatibility.py

@@ -334,10 +334,10 @@ def run_test(self):
         node_v17.createwallet(wallet_name="u1_v17")
         wallet = node_v17.get_wallet_rpc("u1_v17")
         address = wallet.getnewaddress()
-        info = wallet.getaddressinfo(address)
+        v17_info = wallet.getaddressinfo(address)
         # TODO enable back when HD wallets are created by default
-        #hdkeypath = info["hdkeypath"]
-        pubkey = info["pubkey"]
+        #v17_hdkeypath = v17_info["hdkeypath"]
+        v17_pubkey = v17_info["pubkey"]
 
         # Copy the 0.17 wallet to the last Bitcoin Core version and open it:
         node_v17.unloadwallet("u1_v17")
@@ -349,9 +349,21 @@ def run_test(self):
         wallet = node_master.get_wallet_rpc("u1_v17")
         info = wallet.getaddressinfo(address)
         # TODO enable back when HD wallets are created by default
-        #descriptor = "pkh([" + info["hdmasterfingerprint"] + hdkeypath[1:] + "]" + pubkey + ")"
+        #descriptor = "pkh([" + info["hdmasterfingerprint"] + hdkeypath[1:] + "]" + v17_pubkey + ")"
         #assert_equal(info["desc"], descsum_create(descriptor))
-        assert_equal(info["pubkey"], pubkey)
+        assert_equal(info["pubkey"], v17_pubkey)
+
+        # Now copy that same wallet back to 0.17 to make sure no automatic upgrade breaks it
+        node_master.unloadwallet("u1_v17")
+        shutil.rmtree(os.path.join(node_v17_wallets_dir, "u1_v17"))
+        shutil.copytree(
+            os.path.join(node_master_wallets_dir, "u1_v17"),
+            os.path.join(node_v17_wallets_dir, "u1_v17")
+        )
+        node_v17.loadwallet("u1_v17")
+        wallet = node_v17.get_wallet_rpc("u1_v17")
+        info = wallet.getaddressinfo(address)
+        assert_equal(info, v17_info)
 
         # Copy the 0.19 wallet to the last Bitcoin Core version and open it:
         shutil.copytree(
@@ -362,5 +374,16 @@ def run_test(self):
         wallet = node_master.get_wallet_rpc("w1_v19")
         assert wallet.getaddressinfo(address_18075)["solvable"]
 
+        # Now copy that same wallet back to 0.19 to make sure no automatic upgrade breaks it
+        node_master.unloadwallet("w1_v19")
+        shutil.rmtree(os.path.join(node_v19_wallets_dir, "w1_v19"))
+        shutil.copytree(
+            os.path.join(node_master_wallets_dir, "w1_v19"),
+            os.path.join(node_v19_wallets_dir, "w1_v19")
+        )
+        node_v19.loadwallet("w1_v19")
+        wallet = node_v19.get_wallet_rpc("w1_v19")
+        assert wallet.getaddressinfo(address_18075)["solvable"]
+
 if __name__ == '__main__':
     BackwardsCompatibilityTest().main()