Support wallet.dat outside of datadir

Ported from 6a7cfdea54
which did not apply cleanly.

qa/rpc-tests/feature_walletfile.py

@@ -0,0 +1,51 @@
+#!/usr/bin/env python3
+# Copyright (c) 2017      The Bitcoin Core developers
+# Copyright (c) 2019-2020 The Hush developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or https://www.opensource.org/licenses/mit-license.php
+"""Test wallet file location."""
+
+import os
+
+from test_framework.util import start_node, stop_node, assert_start_raises_init_error
+
+from test_framework.test_framework import BitcoinTestFramework
+
+class WalletFileTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+        self.setup_clean_chain = True
+
+    def run_test(self):
+        # test default wallet location
+        assert os.path.isfile(os.path.join(self.options.tmpdir, "node0", "regtest", "wallet.dat"))
+
+        # test alternative wallet file name in datadir
+        stop_node(self.nodes[0], 0)
+        self.nodes[0] = start_node(0, self.options.tmpdir, ["-wallet=altwallet.dat"])
+        assert os.path.isfile(os.path.join(self.options.tmpdir, "node0", "regtest", "altwallet.dat"))
+
+        # test wallet file outside datadir
+        tempname = os.path.join(self.options.tmpdir, "outsidewallet.dat")
+        stop_node(self.nodes[0], 0)
+        self.nodes[0] = start_node(0, self.options.tmpdir, ["-wallet=%s" % tempname])
+        assert os.path.isfile(tempname)
+
+        # test the case where absolute path does not exist
+        assert not os.path.isdir("/this_directory_must_not_exist")
+        invalidpath = os.path.join("/this_directory_must_not_exist/", "foo.dat")
+        stop_node(self.nodes[0], 0)
+        assert_start_raises_init_error(0, "-wallet=%s" % invalidpath,
+            "Error: Absolute path %s does not exist")
+
+        # relative path does not exist
+        invalidpath = os.path.join("wallet", "foo.dat")
+        assert_start_raises_init_error(0, "-wallet=%s" % invalidpath,
+            "Error: Relative path %s does not exist")
+
+        # create dir and retry
+        os.mkdir(os.path.join(self.options.tmpdir, "node0", "regtest", "wallet"))
+        self.nodes[0] = start_node(0, self.options.tmpdir, ["-wallet=%s" % invalidpath])
+
+if __name__ == '__main__':
+    WalletFileTest().main()