Fix Lua table field builder slot generation

src/bfbs_gen_lua.cpp

@@ -554,7 +554,7 @@ class LuaBfbsGenerator : public BaseBfbsGenerator {
     if (IsScalar(base_type)) {
       return namer_.Type(GenerateType(base_type));
     }
-    if (IsStructOrTable(base_type)) {
+    if (base_type == r::Obj && GetObject(field->type())->is_struct()) {
       return "Struct";
     }
     return "UOffsetTRelative";

tests/LuaTest.sh

@@ -17,6 +17,8 @@
 pushd "$(dirname $0)" >/dev/null
 test_dir="$(pwd)"
 
+${test_dir}/../flatc -l -o ${test_dir} lua_nested_table_test.fbs
+
 declare -a versions=(luajit lua5.1 lua5.2 lua5.3 lua5.4)
 
 for i in "${versions[@]}"

tests/lua_nested_table_test.fbs

@@ -0,0 +1,11 @@
+table Customer {
+  name:string;
+  age:int;
+}
+
+table Sale {
+  amount:int;
+  customer:Customer;
+}
+
+root_type Sale;

tests/luatest.lua

@@ -317,6 +317,26 @@ local function testAccessByteVectorAsString()
     end
 end
 
+local function testLuaNestedTablePack()
+    local sale = assert(require("Sale"))
+    local customer = assert(require("Customer"))
+    local builder = flatbuffers.Builder(0)
+
+    local name = builder:CreateString("Alice")
+    customer.Start(builder)
+    customer.AddName(builder, name)
+    customer.AddAge(builder, 33)
+    local customerOffset = customer.End(builder)
+
+    sale.Start(builder)
+    sale.AddAmount(builder, 125)
+    sale.AddCustomer(builder, customerOffset)
+    local saleOffset = sale.End(builder)
+    builder:Finish(saleOffset)
+
+    assert(#builder:Output() > 0)
+end
+
 local tests = 
 { 
     {   
@@ -344,6 +364,10 @@ local tests =
         f = testAccessByteVectorAsString,
         d = "Access byte vector as string"
     },
+    {
+        f = testLuaNestedTablePack,
+        d = "Lua nested table fields pack with UOffset slots"
+    },
 }
 
 local benchmarks =