Modernize lua read (part 2 & 3): C++ templating assurance (#7410)

* Modernize lua read (part 2 & 3): C++ templating assurance

Implement the boolean reader
Implement the string reader
Also remove unused & unimplemented script_error_handler
Add a reader with default value

4 files changed, 129 insertions, 2 deletions

diff --git a/src/script/common/CMakeLists.txt b/src/script/common/CMakeLists.txt
index 4a8e6bab5..d07f6ab1b 100644
--- a/src/script/common/CMakeLists.txt
+++ b/src/script/common/CMakeLists.txt
@@ -3,6 +3,7 @@ set(common_SCRIPT_COMMON_SRCS
 	${CMAKE_CURRENT_SOURCE_DIR}/c_converter.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/c_types.cpp
 	${CMAKE_CURRENT_SOURCE_DIR}/c_internal.cpp
+	${CMAKE_CURRENT_SOURCE_DIR}/helper.cpp
 	PARENT_SCOPE)
 
 set(client_SCRIPT_COMMON_SRCS
diff --git a/src/script/common/c_internal.h b/src/script/common/c_internal.h
index 35477375b..d2131d1ad 100644
--- a/src/script/common/c_internal.h
+++ b/src/script/common/c_internal.h
@@ -95,11 +95,10 @@ enum RunCallbacksMode
 	// after seeing the first true value
 	RUN_CALLBACKS_MODE_OR_SC,
 	// Note: "a true value" and "a false value" refer to values that
-	// are converted by lua_toboolean to true or false, respectively.
+	// are converted by readParam<bool> to true or false, respectively.
 };
 
 std::string script_get_backtrace(lua_State *L);
-int script_error_handler(lua_State *L);
 int script_exception_wrapper(lua_State *L, lua_CFunction f);
 void script_error(lua_State *L, int pcall_result, const char *mod, const char *fxn);
 void script_run_callbacks_f(lua_State *L, int nargs,
diff --git a/src/script/common/helper.cpp b/src/script/common/helper.cpp
new file mode 100644
index 000000000..9adc56a65
--- /dev/null
+++ b/src/script/common/helper.cpp
@@ -0,0 +1,73 @@
+/*
+Minetest
+Copyright (C) 2018 nerzhul, Loic Blot <loic.blot@unix-experience.fr>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#include "helper.h"
+#include <cmath>
+#include <sstream>
+#include "c_types.h"
+
+bool LuaHelper::isNaN(lua_State *L, int idx)
+{
+	return lua_type(L, idx) == LUA_TNUMBER && std::isnan(lua_tonumber(L, idx));
+}
+
+/*
+ * Read template functions
+ */
+template <> bool LuaHelper::readParam(lua_State *L, int index)
+{
+	return lua_toboolean(L, index) != 0;
+}
+
+template <> bool LuaHelper::readParam(lua_State *L, int index, const bool &default_value)
+{
+	if (lua_isnil(L, index))
+		return default_value;
+
+	return lua_toboolean(L, index) != 0;
+}
+
+template <> float LuaHelper::readParam(lua_State *L, int index)
+{
+	if (isNaN(L, index))
+		throw LuaError("NaN value is not allowed.");
+
+	return (float)luaL_checknumber(L, index);
+}
+
+template <> std::string LuaHelper::readParam(lua_State *L, int index)
+{
+	std::string result;
+	const char *str = luaL_checkstring(L, index);
+	result.append(str);
+	return result;
+}
+
+template <>
+std::string LuaHelper::readParam(
+		lua_State *L, int index, const std::string &default_value)
+{
+	std::string result;
+	const char *str = lua_tostring(L, index);
+	if (str)
+		result.append(str);
+	else
+		result = default_value;
+	return result;
+}
diff --git a/src/script/common/helper.h b/src/script/common/helper.h
new file mode 100644
index 000000000..d639d6e16
--- /dev/null
+++ b/src/script/common/helper.h
@@ -0,0 +1,54 @@
+/*
+Minetest
+Copyright (C) 2018 nerzhul, Loic Blot <loic.blot@unix-experience.fr>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+
+extern "C" {
+#include <lua.h>
+#include <lauxlib.h>
+}
+
+class LuaHelper
+{
+protected:
+	static bool isNaN(lua_State *L, int idx);
+
+	/**
+	 * Read a value using a template type T from Lua State L and index
+	 *
+	 *
+	 * @tparam T type to read from Lua
+	 * @param L Lua state
+	 * @param index Lua Index to read
+	 * @return read value from Lua
+	 */
+	template <typename T> static T readParam(lua_State *L, int index);
+
+	/**
+	 * Read a value using a template type T from Lua State L and index
+	 *
+	 * @tparam T type to read from Lua
+	 * @param L Lua state
+	 * @param index Lua Index to read
+	 * @param default_value default value to apply if nil
+	 * @return read value from Lua or default value if nil
+	 */
+	template <typename T>
+	static T readParam(lua_State *L, int index, const T &default_value);
+};