bugfix: Fix incorrect debug.log config file path

Currently debug.log will show the wrong bitcoin.conf config file path when
bitcoind is invoked without -conf or -datadir arguments, and there's a default
bitcoin.conf file which specifies another datadir= location. When this happens,
the debug.log will include an incorrect "Config file:" line referring to a
bitcoin.conf file in the other datadir, instead of the referring to the actual
configuration file in the default datadir which was parsed.

The bad log print was reported and originally fixed in
https://github.com/bitcoin/bitcoin/pull/27303 by
Matthew Zipkin <pinheadmz@gmail.com>

This PR takes a slightly different approach to fixing the bug, trying to avoid
future bugs by not allowing the GetConfigFilePath function to be called before
the the configuration is parsed, and deleting GetConfigFile function which
could be confused with GetConfigFilePath. It also includes a test for the bug
which the original fix did not have.

Co-authored-by: Matthew Zipkin <pinheadmz@gmail.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/test/functional/feature_config_args.py b/test/functional/feature_config_args.py
index a45888513f..2257605870 100755
--- a/test/functional/feature_config_args.py
+++ b/test/functional/feature_config_args.py
@@ -113,6 +113,41 @@ class ConfArgsTest(BitcoinTestFramework):
         with open(inc_conf_file2_path, 'w', encoding='utf-8') as conf:
             conf.write('')  # clear
 
+    def test_config_file_log(self):
+        # Disable this test for windows currently because trying to override
+        # the default datadir through the environment does not seem to work.
+        if sys.platform == "win32":
+            return
+
+        self.log.info('Test that correct configuration path is changed when configuration file changes the datadir')
+
+        # Create a temporary directory that will be treated as the default data
+        # directory by bitcoind.
+        env, default_datadir = util.get_temp_default_datadir(pathlib.Path(self.options.tmpdir, "test_config_file_log"))
+        default_datadir.mkdir(parents=True)
+
+        # Write a bitcoin.conf file in the default data directory containing a
+        # datadir= line pointing at the node datadir.
+        node = self.nodes[0]
+        conf_text = pathlib.Path(node.bitcoinconf).read_text()
+        conf_path = default_datadir / "bitcoin.conf"
+        conf_path.write_text(f"datadir={node.datadir}\n{conf_text}")
+
+        # Drop the node -datadir= argument during this test, because if it is
+        # specified it would take precedence over the datadir setting in the
+        # config file.
+        node_args = node.args
+        node.args = [arg for arg in node.args if not arg.startswith("-datadir=")]
+
+        # Check that correct configuration file path is actually logged
+        # (conf_path, not node.bitcoinconf)
+        with self.nodes[0].assert_debug_log(expected_msgs=[f"Config file: {conf_path}"]):
+            self.start_node(0, ["-allowignoredconf"], env=env)
+            self.stop_node(0)
+
+        # Restore node arguments after the test
+        node.args = node_args
+
     def test_invalid_command_line_options(self):
         self.nodes[0].assert_start_raises_init_error(
             expected_msg='Error: Error parsing command line arguments: Can not set -proxy with no value. Please specify value with -proxy=value.',
@@ -344,6 +379,7 @@ class ConfArgsTest(BitcoinTestFramework):
         self.test_connect_with_seednode()
 
         self.test_config_file_parser()
+        self.test_config_file_log()
         self.test_invalid_command_line_options()
         self.test_ignored_conf()
         self.test_ignored_default_conf()