Supports the new idiomatic .new() for constructors

Author: kunitoki

Distribution/LuaBridge/LuaBridge.h

@@ -8813,7 +8813,7 @@ int constructor_container_proxy(lua_State* L)
     try
     {
 #endif
-        object = constructor<T, Args>::construct(detail::make_arguments_list<Args, 2>(L));
+        object = constructor<T, Args>::construct(detail::make_arguments_list<Args, 1>(L));
 
 #if LUABRIDGE_HAS_EXCEPTIONS
     }
@@ -8833,7 +8833,7 @@ int constructor_container_proxy(lua_State* L)
 template <class T, class Args>
 int constructor_placement_proxy(lua_State* L)
 {
-    auto args = make_arguments_list<Args, 2>(L);
+    auto args = make_arguments_list<Args, 1>(L);
 
     std::error_code ec;
     auto* value = UserdataValue<T>::place(L, ec);
@@ -8873,7 +8873,7 @@ struct constructor_forwarder
         using FnTraits = function_traits<F>;
         using FnArgs = remove_first_type_t<typename FnTraits::argument_types>;
 
-        auto args = make_arguments_list<FnArgs, 2>(L);
+        auto args = make_arguments_list<FnArgs, 1>(L);
 
         std::error_code ec;
         auto* value = UserdataValue<T>::place(L, ec);
@@ -8988,7 +8988,7 @@ struct container_forwarder
         try
         {
 #endif
-            object = container_constructor<C>::construct(m_func, make_arguments_list<FnArgs, 2>(L));
+            object = container_constructor<C>::construct(m_func, make_arguments_list<FnArgs, 1>(L));
 
 #if LUABRIDGE_HAS_EXCEPTIONS
         }
@@ -9408,7 +9408,7 @@ inline ClassInspectInfo inspectClassFromStaticTable(lua_State* L, int stIdx)
                 {
                     MemberInfo m;
                     m.name = key;
-                    if (key == "__call")
+                    if (key == "new")
                         m.kind = MemberKind::Constructor;
                     else if (key.size() >= 2 && key[0] == '_' && key[1] == '_')
                         m.kind = MemberKind::Metamethod;
@@ -10072,10 +10072,10 @@ class LuaProxyVisitor : public InspectVisitor
         {
         case MemberKind::Constructor:
 
-            out_ << "setmetatable(" << qname << ", {__call = function(t";
+            out_ << qname << ".new = function(";
             if (!m.overloads[0].params.empty())
-                out_ << ", " << paramNames(m.overloads[0].params);
-            out_ << ")\n    return setmetatable({}, t)\nend})\n\n";
+                out_ << paramNames(m.overloads[0].params);
+            out_ << ") end\n\n";
             break;
 
         case MemberKind::Method:
@@ -13412,10 +13412,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call");
+            rawsetfield(L, -2, "new");
 
             return *this;
         }
@@ -13509,10 +13509,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call"); 
+            rawsetfield(L, -2, "new"); 
 
             return *this;
         }
@@ -13558,10 +13558,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call");
+            rawsetfield(L, -2, "new");
 
             return *this;
         }
@@ -13623,10 +13623,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call"); 
+            rawsetfield(L, -2, "new"); 
 
             return *this;
         }
@@ -13659,7 +13659,7 @@ class Namespace : public detail::Registrar
 
             lua_newuserdata_aligned<F>(L, F(std::move(allocator), std::move(deallocator))); 
             lua_pushcclosure_x(L, &detail::invoke_proxy_constructor<F>, className, 1); 
-            rawsetfield(L, -2, "__call"); 
+            rawsetfield(L, -2, "new"); 
 
             return *this;
         }

Manual.md

@@ -732,12 +732,12 @@ luabridge::getGlobalNamespace (L)
   .endNamespace ();
 ```
 
-Constructors added in this fashion are called from Lua using the fully qualified name of the class. This Lua code will create instances of `A` and `B`.
+Constructors added in this fashion are called from Lua using the `.new` field on the class. This Lua code will create instances of `A` and `B`.
 
 ```lua
-a = test.A ()           -- Create a new A.
-b = test.B ("hello", 5) -- Create a new B.
-b = test.B ()           -- Error: expected string in argument 1
+a = test.A.new ()           -- Create a new A.
+b = test.B.new ("hello", 5) -- Create a new B.
+b = test.B.new ()           -- Error: expected string in argument 1
 ```
 
 ### 2.6.1 - Constructor Proxies
@@ -764,16 +764,16 @@ luabridge::getGlobalNamespace (L)
 Then in lua:
 
 ```lua
-hard = test.HardToCreate (5) -- Create a new HardToCreate.
+hard = test.HardToCreate.new (5) -- Create a new HardToCreate.
 ```
 
-The `addConstructor` overload taking a generic functor also accepts a `lua_State*` as last parameter in order to be used for constructors that needs to be overloaded by different numbers of arguments (arguments will start at index 2 of the stack):
+The `addConstructor` overload taking a generic functor also accepts a `lua_State*` as last parameter in order to be used for constructors that needs to be overloaded by different numbers of arguments (arguments will start at index 1 of the stack):
 
 ```cpp
 luabridge::getGlobalNamespace (L)
   .beginNamespace ("test")
     .beginClass<HardToCreate> ("HardToCreate")
-      .addConstructor ([] (void* ptr, lua_State* L) { return new (ptr) HardToCreate (shouldNotSeeMe, lua_checkinteger (L, 2)); })
+      .addConstructor ([] (void* ptr, lua_State* L) { return new (ptr) HardToCreate (shouldNotSeeMe, lua_checkinteger (L, 1)); })
     .endClass ()
   .endNamespace ();
 ```
@@ -826,7 +826,7 @@ luabridge::getGlobalNamespace (L)
 The object is the perfectly instantiable through lua:
 
 ```lua
-a = test.Object ()           -- Create a new Object using objectFactoryAllocator
+a = test.Object.new ()           -- Create a new Object using objectFactoryAllocator
 a = nil                      -- Remove any reference count
 collectgarbage ("collect")   -- The object is garbage collected using objectFactoryDeallocator
 ```

Source/LuaBridge/Inspect.h

@@ -468,7 +468,7 @@ inline ClassInspectInfo inspectClassFromStaticTable(lua_State* L, int stIdx)
                 {
                     MemberInfo m;
                     m.name = key;
-                    if (key == "__call")
+                    if (key == "new")
                         m.kind = MemberKind::Constructor;
                     else if (key.size() >= 2 && key[0] == '_' && key[1] == '_')
                         m.kind = MemberKind::Metamethod;
@@ -1008,7 +1008,7 @@ class LuaLSVisitor : public InspectVisitor
         case MemberKind::Constructor:
         {
             // Represent the constructor as @overload annotations before the local declaration.
-            // LuaBridge constructors are called as ClassName(args), not ClassName.new(args).
+            // LuaBridge constructors are called as ClassName.new(args).
             std::string qname = qualifiedName(cls.name);
             for (const auto& ov : m.overloads)
                 out_ << "---@overload fun(" << overloadParams(ov.params) << "): " << qname << "\n";
@@ -1202,11 +1202,11 @@ class LuaProxyVisitor : public InspectVisitor
         switch (m.kind)
         {
         case MemberKind::Constructor:
-            // LuaBridge constructors are called as ClassName(args) via __call metamethod.
-            out_ << "setmetatable(" << qname << ", {__call = function(t";
+            // LuaBridge constructors are called as ClassName.new(args).
+            out_ << qname << ".new = function(";
             if (!m.overloads[0].params.empty())
-                out_ << ", " << paramNames(m.overloads[0].params);
-            out_ << ")\n    return setmetatable({}, t)\nend})\n\n";
+                out_ << paramNames(m.overloads[0].params);
+            out_ << ") end\n\n";
             break;
 
         case MemberKind::Method:

Source/LuaBridge/detail/CFunctions.h

@@ -2009,8 +2009,6 @@ bool overload_type_checker(lua_State* L, int start)
  *   2. Type check via Stack<T>::isInstance in C++ (no pcall) — skips clearly mismatched overloads.
  *   3. Only calls lua_pcall for type-matched candidates, eliminating failed pcalls for type mismatches.
  */
-
-
 template <bool Member>
 inline int try_overload_functions(lua_State* L)
 {
@@ -2890,7 +2888,7 @@ int constructor_container_proxy(lua_State* L)
     try
     {
 #endif
-        object = constructor<T, Args>::construct(detail::make_arguments_list<Args, 2>(L));
+        object = constructor<T, Args>::construct(detail::make_arguments_list<Args, 1>(L));
 
 #if LUABRIDGE_HAS_EXCEPTIONS
     }
@@ -2913,7 +2911,7 @@ int constructor_container_proxy(lua_State* L)
 template <class T, class Args>
 int constructor_placement_proxy(lua_State* L)
 {
-    auto args = make_arguments_list<Args, 2>(L);
+    auto args = make_arguments_list<Args, 1>(L);
 
     std::error_code ec;
     auto* value = UserdataValue<T>::place(L, ec);
@@ -2957,7 +2955,7 @@ struct constructor_forwarder
         using FnTraits = function_traits<F>;
         using FnArgs = remove_first_type_t<typename FnTraits::argument_types>;
 
-        auto args = make_arguments_list<FnArgs, 2>(L);
+        auto args = make_arguments_list<FnArgs, 1>(L);
 
         std::error_code ec;
         auto* value = UserdataValue<T>::place(L, ec);
@@ -3084,7 +3082,7 @@ struct container_forwarder
         try
         {
 #endif
-            object = container_constructor<C>::construct(m_func, make_arguments_list<FnArgs, 2>(L));
+            object = container_constructor<C>::construct(m_func, make_arguments_list<FnArgs, 1>(L));
 
 #if LUABRIDGE_HAS_EXCEPTIONS
         }

Source/LuaBridge/detail/Namespace.h

@@ -1262,7 +1262,7 @@ class Namespace : public detail::Registrar
         /**
          * @brief Add or replace a primary Constructor.
          *
-         * The primary Constructor is invoked when calling the class type table like a function.
+         * The primary Constructor is invoked by calling `ClassName.new(args...)`.
          *
          * The template parameter should be a function pointer type that matches the desired Constructor (since you can't take the
          * address of a Constructor and pass it as an argument).
@@ -1337,10 +1337,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call");
+            rawsetfield(L, -2, "new");
 
             return *this;
         }
@@ -1349,10 +1349,10 @@ class Namespace : public detail::Registrar
         /**
          * @brief Add or replace a placement constructor.
          *
-         * The primary placement constructor is invoked when calling the class type table like a function.
+         * The primary placement constructor is invoked by calling `ClassName.new(args...)`.
          *
          * The provider of the Function argument is responsible of doing placement new of the type T over the void* pointer provided to
-         * the method as first argument.
+         * the method as first argument. Invoked by calling `ClassName.new(args...)`.
          */
         template <class... Functions>
         auto addConstructor(Functions... functions)
@@ -1445,10 +1445,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call"); // Stack: co, cl, st
+            rawsetfield(L, -2, "new"); // Stack: co, cl, st
 
             return *this;
         }
@@ -1499,10 +1499,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call");
+            rawsetfield(L, -2, "new");
 
             return *this;
         }
@@ -1571,10 +1571,10 @@ class Namespace : public detail::Registrar
 
                 } (), ...);
 
-                lua_pushcclosure_x(L, &detail::try_overload_functions<true>, className, 2);
+                lua_pushcclosure_x(L, &detail::try_overload_functions<false>, className, 2);
             }
 
-            rawsetfield(L, -2, "__call"); // Stack: co, cl, st
+            rawsetfield(L, -2, "new"); // Stack: co, cl, st
 
             return *this;
         }
@@ -1603,7 +1603,7 @@ class Namespace : public detail::Registrar
         /**
          * @brief Add or replace a factory.
          *
-         * The primary Constructor is invoked when calling the class type table like a function.
+         * The factory is invoked by calling `ClassName.new()`.
          *
          * The template parameter should be a function pointer type that matches the desired Constructor (since you can't take the
          * address of a Constructor and pass it as an argument).
@@ -1617,7 +1617,7 @@ class Namespace : public detail::Registrar
 
             lua_newuserdata_aligned<F>(L, F(std::move(allocator), std::move(deallocator))); // Stack: co, cl, st, upvalue
             lua_pushcclosure_x(L, &detail::invoke_proxy_constructor<F>, className, 1); // Stack: co, cl, st, function
-            rawsetfield(L, -2, "__call"); // Stack: co, cl, st
+            rawsetfield(L, -2, "new"); // Stack: co, cl, st
 
             return *this;
         }

Tests/Source/ArrayTests.cpp

@@ -117,12 +117,12 @@ TEST_F(ArrayTests, PassFromLua)
         .addFunction("processPointers", &processPointers<3>);
 
     resetResult();
-    runLua("result = processValues ({Data (-1), Data (2), Data (5)})");
+    runLua("result = processValues ({Data.new(-1), Data.new(2), Data.new(5)})");
 
     ASSERT_EQ((std::array<Data, 3>({-1, 2, 5})), (result<std::array<Data, 3>>()));
 
     resetResult();
-    runLua("result = processPointers ({Data (-3), Data (4), Data (9)})");
+    runLua("result = processPointers ({Data.new(-3), Data.new(4), Data.new(9)})");
 
     ASSERT_EQ((std::array<Data, 3>({-3, 4, 9})), (result<std::array<Data, 3>>()));
 }