args: Properly support -noconf

-noconf would previously lead to an ifstream "successfully" being opened to the ".bitcoin"-directory (not a file). (Guards against the general case of directories as configs are added in grandchild commit to this one).

Other users of AbsPathForConfigVal() in combination with negated args have been updated earlier in this PR ("args: Support -nopid" and "args: Support -norpccookiefile...").

src/common/config.cpp

@@ -128,13 +128,15 @@ bool ArgsManager::ReadConfigFiles(std::string& error, bool ignore_invalid_keys)
     }
 
     const auto conf_path{GetConfigFilePath()};
-    std::ifstream stream{conf_path};
+    std::ifstream stream;
-
+    if (!conf_path.empty()) { // path is empty when -noconf is specified
-    // not ok to have a config file specified that cannot be opened
+        stream = std::ifstream{conf_path};
+        // If the file is explicitly specified, it must be readable
         if (IsArgSet("-conf") && !stream.good()) {
             error = strprintf("specified config file \"%s\" could not be opened.", fs::PathToString(conf_path));
             return false;
         }
+    }
     // ok to not have a config file
     if (stream.good()) {
         if (!ReadConfigStream(stream, fs::PathToString(conf_path), error, ignore_invalid_keys)) {
@@ -213,7 +215,7 @@ bool ArgsManager::ReadConfigFiles(std::string& error, bool ignore_invalid_keys)
 
 fs::path AbsPathForConfigVal(const ArgsManager& args, const fs::path& path, bool net_specific)
 {
-    if (path.is_absolute()) {
+    if (path.is_absolute() || path.empty()) {
         return path;
     }
     return fsbridge::AbsPathJoin(net_specific ? args.GetDataDirNet() : args.GetDataDirBase(), path);

src/common/init.cpp

@@ -62,31 +62,38 @@ std::optional<ConfigError> InitConfig(ArgsManager& args, SettingsAbortFn setting
             fs::create_directories(net_path / "wallets");
         }
 
-        // Show an error or warning if there is a bitcoin.conf file in the
+        // Show an error or warn/log if there is a bitcoin.conf file in the
         // datadir that is being ignored.
         const fs::path base_config_path = base_path / BITCOIN_CONF_FILENAME;
-        if (fs::exists(base_config_path) && !fs::equivalent(orig_config_path, base_config_path)) {
+        if (fs::exists(base_config_path)) {
+            if (orig_config_path.empty()) {
+                LogInfo(
+                    "Data directory %s contains a %s file which is explicitly ignored using -noconf.",
+                    fs::quoted(fs::PathToString(base_path)),
+                    fs::quoted(BITCOIN_CONF_FILENAME));
+            } else if (!fs::equivalent(orig_config_path, base_config_path)) {
                 const std::string cli_config_path = args.GetArg("-conf", "");
                 const std::string config_source = cli_config_path.empty()
                     ? strprintf("data directory %s", fs::quoted(fs::PathToString(orig_datadir_path)))
                     : strprintf("command line argument %s", fs::quoted("-conf=" + cli_config_path));
-            const std::string error = strprintf(
+                std::string error = strprintf(
                     "Data directory %1$s contains a %2$s file which is ignored, because a different configuration file "
                     "%3$s from %4$s is being used instead. Possible ways to address this would be to:\n"
                     "- Delete or rename the %2$s file in data directory %1$s.\n"
                     "- Change datadir= or conf= options to specify one configuration file, not two, and use "
-                "includeconf= to include any other configuration files.\n"
+                    "includeconf= to include any other configuration files.",
-                "- Set allowignoredconf=1 option to treat this condition as a warning, not an error.",
                     fs::quoted(fs::PathToString(base_path)),
                     fs::quoted(BITCOIN_CONF_FILENAME),
                     fs::quoted(fs::PathToString(orig_config_path)),
                     config_source);
                 if (args.GetBoolArg("-allowignoredconf", false)) {
-                LogPrintf("Warning: %s\n", error);
+                    LogWarning("%s", error);
                 } else {
+                    error += "\n- Set allowignoredconf=1 option to treat this condition as a warning, not an error.";
                     return ConfigError{ConfigStatus::FAILED, Untranslated(error)};
                 }
             }
+        }
 
         // Create settings.json if -nosettings was not specified.
         if (args.GetSettingsPath()) {

src/init/common.cpp

@@ -17,6 +17,7 @@
 #include <util/translation.h>
 
 #include <algorithm>
+#include <filesystem>
 #include <string>
 #include <vector>
 
@@ -122,10 +123,11 @@ bool StartLogging(const ArgsManager& args)
 
     // Only log conf file usage message if conf file actually exists.
     fs::path config_file_path = args.GetConfigFilePath();
-    if (fs::exists(config_file_path)) {
+    if (args.IsArgNegated("-conf")) {
+        LogInfo("Config file: <disabled>");
+    } else if (fs::exists(config_file_path)) {
         LogPrintf("Config file: %s\n", fs::PathToString(config_file_path));
     } else if (args.IsArgSet("-conf")) {
-        // Warn if no conf file exists at path provided by user
         InitWarning(strprintf(_("The specified config file %s does not exist"), fs::PathToString(config_file_path)));
     } else {
         // Not categorizing as "Warning" because it's the default behavior