Address feedback

* Changed the plugin preference API to use luaW_pushscalar() and
luaW_toscalar() to handle preference values.
* Set the __metatable field in the "preferences" table, which blocks Lua
code from changing the metatable and allows developers to query where the
metatable originates.
* Added empty lines to the end of new files.

src/preferences.cpp

@@ -194,6 +194,11 @@ void set(const std::string &key, const std::string &value)
 	prefs[key] = value;
 }
 
+void set(const std::string &key, const config::attribute_value &value)
+{
+	prefs[key] = value;
+}
+
 void clear(const std::string& key)
 {
 	prefs.recursive_clear_value(key);
@@ -230,6 +235,11 @@ bool get(const std::string &key, bool def)
 	return prefs[key].to_bool(def);
 }
 
+config::attribute_value get_as_attribute(const std::string &key)
+{
+	return prefs[key];
+}
+
 void disable_preferences_save() {
 	no_preferences_save = true;
 }

src/preferences.hpp

@@ -17,9 +17,9 @@
 #ifndef PREFERENCES_HPP_INCLUDED
 #define PREFERENCES_HPP_INCLUDED
 
-class config;
 class display;
 
+#include "config.hpp"
 #include "terrain/translation.hpp"
 
 #include <SDL.h>
@@ -52,14 +52,16 @@ namespace preferences {
 
 	void set(const std::string& key, const std::string &value);
 	void set(const std::string& key, char const *value);
-	void set(const std::string &key, bool value);
-	void set(const std::string &key, int value);
+	void set(const std::string& key, bool value);
+	void set(const std::string& key, int value);
+	void set(const std::string& key, const config::attribute_value& value);
 	void clear(const std::string& key);
 	void set_child(const std::string& key, const config& val);
 	const config &get_child(const std::string &key);
 	std::string get(const std::string& key);
 	std::string get(const std::string& key, const std::string& def);
-	bool get(const std::string &key, bool def);
+	bool get(const std::string& key, bool def);
+	config::attribute_value get_as_attribute(const std::string& key);
 	void erase(const std::string& key);
 	bool have_setting(const std::string& key);
 

src/scripting/lua_preferences.cpp

@@ -1,20 +1,21 @@
 #include "lua_preferences.hpp"
 
+#include <config.hpp>
 #include <lua/lua.h>
 #include <lua/lauxlib.h>
 #include <preferences.hpp>
+#include <scripting/lua_common.hpp>
 
 /**
  * The __index metamethod.
  * Parameter 1: the preference table.
  * Parameter 2: preference name, must be a string.
- * Returns: preference value. Returned as a string regardless of the type of the preference.
- * If there isn't such a preference, returns an empty string.
+ * Returns: preference value. If there isn't such a preference, returns nil.
  */
 static int impl_preferences_get(lua_State* L)
 {
 	std::string preference_name = luaL_checkstring(L, 2);
-	lua_pushstring(L, preferences::get(preference_name).c_str());
+	luaW_pushscalar(L, preferences::get_as_attribute(preference_name));
 	return 1;
 }
 
@@ -22,30 +23,15 @@ static int impl_preferences_get(lua_State* L)
  * The __newindex metamethod.
  * Parameter 1: the preference table.
  * Parameter 2: preference name, must be a string.
- * Parameter 3: preference value. Can be a string, boolean or integer.
+ * Parameter 3: preference value.
  * Returns nothing.
  */
 static int impl_preferences_set(lua_State* L)
 {
 	std::string preference_name = luaL_checkstring(L, 2);
-	int type = lua_type(L, 3);
-
-	switch (type)
-	{
-	case LUA_TSTRING:
-		preferences::set(preference_name, luaL_checkstring(L, 3));
-		break;
-	case LUA_TBOOLEAN:
-		preferences::set(preference_name, lua_toboolean(L, 3) == 1);
-		break;
-	case LUA_TNUMBER:
-		preferences::set(preference_name, luaL_checkint(L, 3));
-		break;
-	default:
-		return luaL_typerror(L, 3, "string/boolean/number");
-		break;
-	}
-
+	config::attribute_value value;
+	luaW_toscalar(L, 3, value);
+	preferences::set(preference_name, value);
 	return 0;
 }
 
@@ -62,6 +48,8 @@ namespace lua_preferences
 		lua_setfield(L, -2, "__index");
 		lua_pushcfunction(L, impl_preferences_set);
 		lua_setfield(L, -2, "__newindex");
+		lua_pushstring(L, "src/scripting/lua_preferences.cpp");
+		lua_setfield(L, -2, "__metatable");
 
 		// Set the table as its own metatable
 		lua_pushvalue(L, -1);
@@ -75,4 +63,4 @@ namespace lua_preferences
 
 		return "Adding preferences table...\n";
 	}
-}
+}

src/scripting/lua_preferences.hpp

@@ -24,4 +24,4 @@ namespace lua_preferences
 	std::string register_table(lua_State* L);
 }
 
-#endif
+#endif