1 files changed, 35 insertions, 4 deletions

diff --git a/src/Bindings/LuaState.h b/src/Bindings/LuaState.h
index 60ae840b0..303a59327 100644
--- a/src/Bindings/LuaState.h
+++ b/src/Bindings/LuaState.h
@@ -309,6 +309,24 @@ public:
 	typedef UniquePtr<cTableRef> cTableRefPtr;
 
 
+	/** Represents a parameter that is optional - calling a GetStackValue() with this object will not fail if the value on the Lua stack is nil.
+	Note that the GetStackValue() will still fail if the param is present but of a different type.
+	The class itself is just a marker so that the template magic will select the correct GetStackValue() overload. */
+	template <typename T>
+	class cOptionalParam
+	{
+	public:
+		explicit cOptionalParam(T & a_Dest):
+			m_Dest(a_Dest)
+		{
+		}
+
+		T & GetDest(void) { return m_Dest; }
+
+	protected:
+		T & m_Dest;
+	};
+
 	/** A dummy class that's used only to delimit function args from return values for cLuaState::Call() */
 	class cRet
 	{
@@ -475,6 +493,7 @@ public:
 
 	// Push a const value onto the stack (keep alpha-sorted):
 	void Push(const AString & a_String);
+	void Push(const AStringMap & a_Dictionary);
 	void Push(const AStringVector & a_Vector);
 	void Push(const cCraftingGrid * a_Grid);
 	void Push(const cCraftingRecipe * a_Recipe);
@@ -508,6 +527,7 @@ public:
 	// Returns whether value was changed
 	// Enum values are checked for their allowed values and fail if the value is not assigned.
 	bool GetStackValue(int a_StackPos, AString & a_Value);
+	bool GetStackValue(int a_StackPos, AStringMap & a_Value);
 	bool GetStackValue(int a_StackPos, bool & a_Value);
 	bool GetStackValue(int a_StackPos, cCallback & a_Callback);
 	bool GetStackValue(int a_StackPos, cCallbackPtr & a_Callback);
@@ -549,6 +569,17 @@ public:
 		return true;
 	}
 
+	/** Retrieves an optional value on the stack - doesn't fail if the stack contains nil instead of the value. */
+	template <typename T>
+	bool GetStackValue(int a_StackPos, cOptionalParam<T> && a_ReturnedVal)
+	{
+		if (lua_isnoneornil(m_LuaState, a_StackPos))
+		{
+			return true;
+		}
+		return GetStackValue(a_StackPos, a_ReturnedVal.GetDest());
+	}
+
 	/** Pushes the named value in the table at the top of the stack.
 	a_Name may be a path containing multiple table levels, such as "cChatColor.Blue".
 	If the value is found, it is pushed on top of the stack and the returned cStackValue is valid.
@@ -606,14 +637,14 @@ public:
 	}
 
 	/** Retrieves a list of values from the Lua stack, starting at the specified index. */
-	template <typename T, typename... Args>
-	inline bool GetStackValues(int a_StartStackPos, T & a_Ret, Args &&... args)
+	template <typename Arg1, typename... Args>
+	inline bool GetStackValues(int a_StartStackPos, Arg1 && a_Arg1, Args &&... args)
 	{
-		if (!GetStackValue(a_StartStackPos, a_Ret))
+		if (!GetStackValue(a_StartStackPos, std::forward<Arg1>(a_Arg1)))
 		{
 			return false;
 		}
-		return GetStackValues(a_StartStackPos + 1, args...);
+		return GetStackValues(a_StartStackPos + 1, std::forward<Args>(args)...);
 	}
 
 	/** Returns true if the specified parameters on the stack are of the specified usertable type; also logs warning if not. Used for static functions */