Node configuration auto updater

nano/core_test/toml.cpp

@@ -1038,3 +1038,47 @@ TEST (toml, log_config_no_required)
 
 	ASSERT_FALSE (toml.get_error ()) << toml.get_error ().get_message ();
 }
+
+TEST (toml, merge_config_files)
+{
+	nano::network_params network_params{ nano::network_constants::active_network };
+	nano::tomlconfig default_toml;
+	nano::tomlconfig current_toml;
+	nano::tomlconfig merged_toml;
+	nano::daemon_config default_config{ ".", network_params };
+	nano::daemon_config current_config{ ".", network_params };
+	nano::daemon_config merged_config{ ".", network_params };
+
+	std::stringstream ss;
+
+	ss << R"toml(
+	[node]
+	 active_elections_size = 999
+	 # backlog_scan_batch_size = 7777
+	[node.bootstrap_ascending]
+	 block_wait_count = 33333
+	 old_entry = 34
+	)toml";
+
+	current_toml.read (ss);
+	current_config.deserialize_toml (current_toml);
+
+	current_config.serialize_toml (current_toml);
+	default_config.serialize_toml (default_toml);
+
+	auto merged_config_string = current_toml.merge_defaults (current_toml, default_toml);
+
+	// Configs have been merged. Let's read and parse the new config file and verify the values
+
+	std::stringstream ss2;
+	ss2 << merged_config_string;
+
+	merged_toml.read (ss2);
+	merged_config.deserialize_toml (merged_toml);
+
+	ASSERT_NE (merged_config.node.active_elections_size, default_config.node.active_elections_size);
+	ASSERT_EQ (merged_config.node.active_elections_size, 999);
+	ASSERT_NE (merged_config.node.backlog_scan_batch_size, 7777);
+	ASSERT_EQ (merged_config.node.bootstrap_ascending.block_wait_count, 33333);
+	ASSERT_TRUE (merged_config_string.find ("old_entry") == std::string::npos);
+}

nano/lib/tomlconfig.cpp

@@ -186,6 +186,38 @@ void nano::tomlconfig::erase_default_values (tomlconfig & defaults_a)
 	erase_defaults (defaults_l.get_tree (), self.get_tree (), get_tree ());
 }
 
+// Merges two TOML configurations and commenting values that are identical
+std::string nano::tomlconfig::merge_defaults (nano::tomlconfig & current_config, nano::tomlconfig & default_config)
+{
+	// Serialize both configs to commented strings
+	std::string defaults_str = default_config.to_string (true);
+	std::string current_str = current_config.to_string (true);
+
+	// Read both configs line by line
+	std::istringstream stream_defaults (defaults_str);
+	std::istringstream stream_current (current_str);
+	std::string line_defaults, line_current, result;
+
+	while (std::getline (stream_defaults, line_defaults) && std::getline (stream_current, line_current))
+	{
+		if (line_defaults == line_current)
+		{
+			// Use default value
+			result += line_defaults + "\n";
+		}
+		else
+		{
+			// Non default value. Removing the # to uncomment
+			size_t pos = line_current.find ('#');
+			debug_assert (pos != std::string::npos);
+			debug_assert (pos < line_current.length ());
+			result += line_current.substr (0, pos) + line_current.substr (pos + 1) + "\n";
+		}
+	}
+
+	return result;
+}
+
 std::string nano::tomlconfig::to_string (bool comment_values)
 {
 	std::stringstream ss, ss_processed;

nano/lib/tomlconfig.hpp

@@ -48,6 +48,7 @@ class tomlconfig : public nano::configbase
 	std::shared_ptr<cpptoml::array> create_array (std::string const & key, boost::optional<char const *> documentation_a);
 	void erase_default_values (tomlconfig & defaults_a);
 	std::string to_string (bool comment_values);
+	std::string merge_defaults (nano::tomlconfig & current_config, nano::tomlconfig & default_config);
 
 	/** Set value for the given key. Any existing value will be overwritten. */
 	template <typename T>

nano/node/cli.cpp

@@ -62,6 +62,7 @@ void nano::add_node_options (boost::program_options::options_description & descr
 	("migrate_database_lmdb_to_rocksdb", "Migrates LMDB database to RocksDB")
 	("diagnostics", "Run internal diagnostics")
 	("generate_config", boost::program_options::value<std::string> (), "Write configuration to stdout, populated with defaults suitable for this system. Pass the configuration type node, rpc or log. See also use_defaults.")
+	("update_config", "Reads the current node configuration and updates it with missing keys and values and delete keys that are no longer used. Updated configuration is written to stdout.")
 	("key_create", "Generates a adhoc random keypair and prints it to stdout")
 	("key_expand", "Derive public key and account number from <key>")
 	("wallet_add_adhoc", "Insert <key> in to <wallet>")
@@ -711,6 +712,31 @@ std::error_code nano::handle_node_options (boost::program_options::variables_map
 			}
 		}
 	}
+	else if (vm.count ("update_config"))
+	{
+		nano::network_params network_params{ nano::network_constants::active_network };
+		nano::tomlconfig default_toml;
+		nano::tomlconfig current_toml;
+		nano::daemon_config default_config{ data_path, network_params };
+		nano::daemon_config current_config{ data_path, network_params };
+
+		std::vector<std::string> config_overrides;
+		auto error = nano::read_node_config_toml (data_path, current_config, config_overrides);
+		if (error)
+		{
+			std::cerr << "Could not read existing config file\n";
+			ec = nano::error_cli::reading_config;
+		}
+		else
+		{
+			current_config.serialize_toml (current_toml);
+			default_config.serialize_toml (default_toml);
+
+			auto output = current_toml.merge_defaults (current_toml, default_toml);
+
+			std::cout << output;
+		}
+	}
 	else if (vm.count ("diagnostics"))
 	{
 		auto inactive_node = nano::default_inactive_node (data_path, vm);