wallet: disallow unnamed wallets in createwallet and restorewallet

Migration still needs to be able to restore unnamed wallets, so
allow_unnamed is added to RestoreWallet to explicitly allow that
behavior for migration only.

test/functional/test_framework/test_node.py

@@ -907,7 +907,6 @@ class TestNode():
     def wait_until(self, test_function, timeout=60, check_interval=0.05):
         return wait_until_helper_internal(test_function, timeout=timeout, timeout_factor=self.timeout_factor, check_interval=check_interval)
 
-
 class TestNodeCLIAttr:
     def __init__(self, cli, command):
         self.cli = cli

test/functional/wallet_backup.py

@@ -184,13 +184,8 @@ class WalletBackupTest(BitcoinTestFramework):
         # This is also useful to test the migration recovery after failure logic
         node = self.nodes[3]
         backup_file = self.nodes[0].datadir_path / 'wallet.bak'
-        wallet_name = ""
-        res = node.restorewallet(wallet_name, backup_file)
-        assert_equal(res['name'], "")
-        assert (node.wallets_path / "wallet.dat").exists()
-        # Clean for follow-up tests
-        node.unloadwallet("")
-        os.remove(node.wallets_path / "wallet.dat")
+        assert_raises_rpc_error(-8, "Wallet name cannot be empty", node.restorewallet, "", backup_file)
+        assert not (node.wallets_path / "wallet.dat").exists()
 
     def test_pruned_wallet_backup(self):
         self.log.info("Test loading backup on a pruned node when the backup was created close to the prune height of the restoring node")
@@ -213,9 +208,8 @@ class WalletBackupTest(BitcoinTestFramework):
 
         self.log.info("Test restore on a pruned node when the backup was beyond the pruning point")
         backup_file = self.nodes[0].datadir_path / 'wallet.bak'
-        wallet_name = ""
         error_message = "Wallet loading failed. Prune: last wallet synchronisation goes beyond pruned data. You need to -reindex (download the whole blockchain again in case of a pruned node)"
-        assert_raises_rpc_error(-4, error_message, node.restorewallet, wallet_name, backup_file)
+        assert_raises_rpc_error(-4, error_message, node.restorewallet, "restore_pruned", backup_file)
         assert node.wallets_path.exists() # ensure the wallets dir exists
 
     def run_test(self):

test/functional/wallet_createwallet.py

@@ -32,6 +32,7 @@ class CreateWalletTest(BitcoinTestFramework):
         # Run createwallet with invalid parameters. This must not prevent a new wallet with the same name from being created with the correct parameters.
         assert_raises_rpc_error(-4, "Passphrase provided but private keys are disabled. A passphrase is only used to encrypt private keys, so cannot be used for wallets with private keys disabled.",
             self.nodes[0].createwallet, wallet_name='w0', disable_private_keys=True, passphrase="passphrase")
+        assert_raises_rpc_error(-8, "Wallet name cannot be empty", self.nodes[0].createwallet, "")
 
         self.nodes[0].createwallet(wallet_name='w0')
         w0 = node.get_wallet_rpc('w0')

test/functional/wallet_startup.py

@@ -6,6 +6,9 @@
 
 Verify that a bitcoind node can maintain list of wallets loading on startup
 """
+import shutil
+import uuid
+
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -24,13 +27,24 @@ class WalletStartupTest(BitcoinTestFramework):
         self.add_nodes(self.num_nodes)
         self.start_nodes()
 
+    def create_unnamed_wallet(self, **kwargs):
+        """
+        createwallet disallows empty wallet names, so create a temporary named wallet
+        and move its wallet.dat to the unnamed wallet location
+        """
+        wallet_name = uuid.uuid4().hex
+        self.nodes[0].createwallet(wallet_name=wallet_name, **kwargs)
+        self.nodes[0].unloadwallet(wallet_name)
+        shutil.move(self.nodes[0].wallets_path / wallet_name / "wallet.dat", self.nodes[0].wallets_path / "wallet.dat")
+        shutil.rmtree(self.nodes[0].wallets_path / wallet_name)
+
     def run_test(self):
         self.log.info('Should start without any wallets')
         assert_equal(self.nodes[0].listwallets(), [])
         assert_equal(self.nodes[0].listwalletdir(), {'wallets': []})
 
         self.log.info('New default wallet should load by default when there are no other wallets')
-        self.nodes[0].createwallet(wallet_name='', load_on_startup=False)
+        self.create_unnamed_wallet(load_on_startup=False)
         self.restart_node(0)
         assert_equal(self.nodes[0].listwallets(), [''])