args: Catch directories in place of config files

Previously passing a directory path as -conf would lead to an ifstream being opened for it, and would not trigger any errors.

Author: hodlinator

src/common/config.cpp

@@ -16,6 +16,7 @@
 #include <algorithm>
 #include <cassert>
 #include <cstdlib>
+#include <filesystem>
 #include <fstream>
 #include <iostream>
 #include <list>
@@ -130,6 +131,10 @@ bool ArgsManager::ReadConfigFiles(std::string& error, bool ignore_invalid_keys)
     const auto conf_path{GetConfigFilePath()};
     std::ifstream stream;
     if (!conf_path.empty()) { // path is empty when -noconf is specified
+        if (fs::is_directory(conf_path)) {
+            error = strprintf("Config file \"%s\" is a directory.", fs::PathToString(conf_path));
+            return false;
+        }
         stream = std::ifstream{conf_path};
         // If the file is explicitly specified, it must be readable
         if (IsArgSet("-conf") && !stream.good()) {
@@ -177,7 +182,12 @@ bool ArgsManager::ReadConfigFiles(std::string& error, bool ignore_invalid_keys)
             const size_t default_includes = add_includes({});
 
             for (const std::string& conf_file_name : conf_file_names) {
-                std::ifstream conf_file_stream{AbsPathForConfigVal(*this, fs::PathFromString(conf_file_name), /*net_specific=*/false)};
+                const auto include_conf_path{AbsPathForConfigVal(*this, fs::PathFromString(conf_file_name), /*net_specific=*/false)};
+                if (fs::is_directory(include_conf_path)) {
+                    error = strprintf("Included config file \"%s\" is a directory.", fs::PathToString(include_conf_path));
+                    return false;
+                }
+                std::ifstream conf_file_stream{include_conf_path};
                 if (conf_file_stream.good()) {
                     if (!ReadConfigStream(conf_file_stream, conf_file_name, error, ignore_invalid_keys)) {
                         return false;

src/init/common.cpp

@@ -125,6 +125,8 @@ bool StartLogging(const ArgsManager& args)
     fs::path config_file_path = args.GetConfigFilePath();
     if (args.IsArgNegated("-conf")) {
         LogInfo("Config file: <disabled>");
+    } else if (fs::is_directory(config_file_path)) {
+        LogWarning("Config file: %s (is directory, not file)", fs::PathToString(config_file_path));
     } else if (fs::exists(config_file_path)) {
         LogPrintf("Config file: %s\n", fs::PathToString(config_file_path));
     } else if (args.IsArgSet("-conf")) {