Fix userdata nil bug (#305)

* Fix userdata nil bug
* Add test to verify userdata nil bug

Author: stefanfrings

Source/LuaBridge/detail/Userdata.h

@@ -575,7 +575,11 @@ struct StackHelper<T, false>
 
     static inline T const& get(lua_State* L, int index)
     {
-        return *Userdata::get<T>(L, index, true);
+        const T* const t = Userdata::get<T>(L, index, true);
+
+        if (!t)
+            luaL_error(L, "nil passed instead of object");
+        return *t;
     }
 };
 

Tests/CMakeLists.txt

@@ -18,6 +18,7 @@ set(LUABRIDGE_TEST_SOURCE_FILES
     Source/TestTypes.h
     Source/TestsMain.cpp
     Source/UnorderedMapTests.cpp
+    Source/UserdataTests.cpp
     Source/VectorTests.cpp
 )
 

Tests/Source/UserdataTests.cpp

@@ -0,0 +1,129 @@
+// https://github.com/vinniefalco/LuaBridge
+// Copyright 2022, Stefan Frings
+// SPDX-License-Identifier: MIT
+
+#include "TestBase.h"
+
+#include "LuaBridge/LuaBridge.h"
+
+class TestClass
+{
+public:
+    explicit inline TestClass(int i) : m_i(i) {}
+
+    inline int get() const { return m_i; }
+
+private:
+    int m_i;
+};
+
+int testFunctionObject(TestClass object)
+{
+    return object.get();
+}
+
+int testFunctionObjectConst(const TestClass object)
+{
+    return object.get();
+}
+
+int testFunctionRef(TestClass& object)
+{
+    return object.get();
+}
+
+int testFunctionRefConst(const TestClass& object)
+{
+    return object.get();
+}
+
+struct UserDataTest : TestBase
+{
+    void SetUp() override
+    {
+        TestBase::SetUp();
+
+        luabridge::getGlobalNamespace(L)
+            .beginClass<TestClass>("TestClass")
+            .addConstructor<void (*)(int)>()
+            .endClass()
+            .
+
+            addFunction("testFunctionObject", testFunctionObject)
+            .addFunction("testFunctionObjectConst", testFunctionObjectConst)
+            .addFunction("testFunctionRef", testFunctionRef)
+            .addFunction("testFunctionRefConst", testFunctionRefConst);
+    }
+};
+
+TEST_F(UserDataTest, Object)
+{
+    runLua("object = TestClass(123)\n"
+           "result = testFunctionObject(object)");
+
+    ASSERT_EQ(result(), 123);
+}
+
+TEST_F(UserDataTest, ObjectConst)
+{
+    runLua("object = TestClass(123)\n"
+           "result = testFunctionObjectConst(object)");
+
+    ASSERT_EQ(result(), 123);
+}
+
+TEST_F(UserDataTest, Ref)
+{
+    runLua("object = TestClass(123)\n"
+           "result = testFunctionRef(object)");
+
+    ASSERT_EQ(result(), 123);
+}
+
+TEST_F(UserDataTest, RefConst)
+{
+    runLua("object = TestClass(123)\n"
+           "result = testFunctionRefConst(object)");
+
+    ASSERT_EQ(result(), 123);
+}
+
+TEST_F(UserDataTest, FailNumberObject)
+{
+    ASSERT_THROW(runLua("testFunctionObject(132)");, std::runtime_error);
+}
+
+TEST_F(UserDataTest, FailNumberObjectConst)
+{
+    ASSERT_THROW(runLua("testFunctionObjectConst(132)");, std::runtime_error);
+}
+
+TEST_F(UserDataTest, FailNumberRef)
+{
+    ASSERT_THROW(runLua("testFunctionRef(132)");, std::runtime_error);
+}
+
+TEST_F(UserDataTest, FailNumberRefConst)
+{
+    ASSERT_THROW(runLua("testFunctionRefConst(132)");, std::runtime_error);
+}
+
+TEST_F(UserDataTest, FailNilObject)
+{
+    ASSERT_THROW(runLua("testFunctionObject(nil)");, std::runtime_error);
+}
+
+TEST_F(UserDataTest, FailNilObjectConst)
+{
+    ASSERT_THROW(runLua("testFunctionObjectConst(nil)");, std::runtime_error);
+}
+
+TEST_F(UserDataTest, FailNilRef)
+{
+    ASSERT_THROW(runLua("testFunctionRef(nil)");, std::runtime_error);
+}
+
+TEST_F(UserDataTest, FailNilRefConst)
+{
+    ASSERT_THROW(runLua("testFunctionRefConst(nil)");, std::runtime_error);
+}