check config file keys for validity, use setValue instead of direct access

src/config.d

@@ -24,7 +24,7 @@ final class Config
 		syncListFilePath = configDirName ~ "/sync_list";
 	}
 
-	void init()
+	bool init()
 	{
 		// Default configuration directory
 		setValue("sync_dir", "~/OneDrive");
@@ -39,10 +39,20 @@ final class Config
 		setValue("monitor_interval", "45");
 		// Configure the default logging directory to be /var/log/onedrive/
 		setValue("log_dir", "/var/log/onedrive/");
+		// Configure a default empty value for drive_id
+		setValue("drive_id", "");
 
 		if (!load(userConfigFilePath)) {
-			log.vlog("No config file found, using defaults");
+			// What was the reason for failure?
+			if (!exists(userConfigFilePath)) {
+				log.vlog("No config file found, using application defaults");
+				return true;
+			} else {
+				log.log("Configuration file has errors - please check your configuration");
+				return false;
+			}
 		}
+		return true;
 	}
 
 	string getValue(string key)
@@ -82,10 +92,17 @@ final class Config
 			if (!c.empty) {
 				c.popFront(); // skip the whole match
 				string key = c.front.dup;
-				c.popFront();
-				values[key] = c.front.dup;
+				auto p = key in values;
+				if (p) {
+					c.popFront();
+					setValue(key, c.front.dup);
+				} else {
+					log.log("Unknown key in config file: ", key);
+					return false;
+				}
 			} else {
 				log.log("Malformed config line: ", line);
+				return false;
 			}
 		}
 		return true;

src/main.d

@@ -152,7 +152,11 @@ int main(string[] args)
 	log.vlog("Using Config Dir: ", configDirName);
 	if (!exists(configDirName)) mkdirRecurse(configDirName);
 	auto cfg = new config.Config(configDirName);
-	cfg.init();
+	if(!cfg.init()){
+		// There was an error loading the configuration
+		// Error message already printed
+		return EXIT_FAILURE;
+	}
 
 	// Configure logging if enabled
 	if (enableLogFile){