The final result types of multiple columns must be transformed element-wise

Author: trueqbit

dev/column_result_proxy.h

@@ -1,5 +1,11 @@
 #pragma once
 
+#ifndef SQLITE_ORM_IMPORT_STD_MODULE
+#include <type_traits>
+#endif
+
+#include "functional/cxx_type_traits_polyfill.h"
+#include "tuple_helper/tuple_transformer.h"
 #include "type_traits.h"
 #include "table_reference.h"
 
@@ -20,22 +26,30 @@ namespace sqlite_orm {
 namespace sqlite_orm {
     namespace internal {
 
+        /*
+         *  Determine the actual and final result type of an intermediate column result produced by `column_result_t`,
+         *  unwrapping `table_reference` and `structure`, and transforming tuples element-wise.
+         */
         template<class T, class SFINAE = void>
         struct column_result_proxy : std::remove_const<T> {};
 
+        template<class T>
+        using column_result_proxy_t = typename column_result_proxy<T>::type;
+
         /*
-         *  Unwrap `table_reference`
+         *  Unwrap `table_reference`, `structure`.
          */
         template<class P>
-        struct column_result_proxy<P, match_if<is_table_reference, P>> : decay_table_ref<P> {};
+        struct column_result_proxy<
+            P,
+            std::enable_if_t<
+                polyfill::disjunction_v<is_table_reference<P>, polyfill::is_specialization_of<P, structure>>>> : P {};
 
         /*
-         *  Pass through `structure`
+         *  Calculate result of multiple columns.
          */
-        template<class P>
-        struct column_result_proxy<P, match_specialization_of<P, structure>> : P {};
-
-        template<class T>
-        using column_result_proxy_t = typename column_result_proxy<T>::type;
+        template<class Tpl>
+        struct column_result_proxy<Tpl, match_specialization_of<Tpl, std::tuple>>
+            : tuple_transformer<Tpl, column_result_proxy_t> {};
     }
 }

include/sqlite_orm/sqlite_orm.h

@@ -10662,6 +10662,14 @@ namespace sqlite_orm {
 
 // #include "column_result_proxy.h"
 
+#ifndef SQLITE_ORM_IMPORT_STD_MODULE
+#include <type_traits>
+#endif
+
+// #include "functional/cxx_type_traits_polyfill.h"
+
+// #include "tuple_helper/tuple_transformer.h"
+
 // #include "type_traits.h"
 
 // #include "table_reference.h"
@@ -10683,23 +10691,31 @@ namespace sqlite_orm {
 namespace sqlite_orm {
     namespace internal {
 
+        /*
+         *  Determine the actual and final result type of an intermediate column result produced by `column_result_t`,
+         *  unwrapping `table_reference` and `structure`, and transforming tuples element-wise.
+         */
         template<class T, class SFINAE = void>
         struct column_result_proxy : std::remove_const<T> {};
 
+        template<class T>
+        using column_result_proxy_t = typename column_result_proxy<T>::type;
+
         /*
-         *  Unwrap `table_reference`
+         *  Unwrap `table_reference`, `structure`.
          */
         template<class P>
-        struct column_result_proxy<P, match_if<is_table_reference, P>> : decay_table_ref<P> {};
+        struct column_result_proxy<
+            P,
+            std::enable_if_t<
+                polyfill::disjunction_v<is_table_reference<P>, polyfill::is_specialization_of<P, structure>>>> : P {};
 
         /*
-         *  Pass through `structure`
+         *  Calculate result of multiple columns.
          */
-        template<class P>
-        struct column_result_proxy<P, match_specialization_of<P, structure>> : P {};
-
-        template<class T>
-        using column_result_proxy_t = typename column_result_proxy<T>::type;
+        template<class Tpl>
+        struct column_result_proxy<Tpl, match_specialization_of<Tpl, std::tuple>>
+            : tuple_transformer<Tpl, column_result_proxy_t> {};
     }
 }
 

tests/static_tests/iterator_t.cpp

@@ -169,20 +169,24 @@ TEST_CASE("can view and iterate result set") {
     STATIC_REQUIRE(
         can_iterate_result_set<result_set_iterator<structure<Object, empty_db_objects_type>, empty_db_objects_type>,
                                Object>);
-#ifdef SQLITE_ORM_WITH_CPP20_ALIASES
     STATIC_REQUIRE(can_iterate_result_set<result_set_iterator<table_reference<Object>, db_objects_type>, Object>);
-#endif
+    STATIC_REQUIRE(can_iterate_result_set<
+                   result_set_iterator<std::tuple<table_reference<Object>, structure<Object, std::tuple<>>, int>,
+                                       db_objects_type>,
+                   std::tuple<Object, Object, int>>);
 
     STATIC_REQUIRE(storage_iterate_result_set<empty_storage_type, decltype(select(42)), int>);
     STATIC_REQUIRE(
         storage_iterate_result_set<empty_storage_type, decltype(select(columns(1, 42))), std::tuple<int, int>>);
     STATIC_REQUIRE(storage_iterate_result_set<empty_storage_type,
                                               decltype(select(struct_<Object>())),
                                               structure<Object, std::tuple<>>>);
-#ifdef SQLITE_ORM_WITH_CPP20_ALIASES
     STATIC_REQUIRE(
         storage_iterate_result_set<storage_type, decltype(select(object<Object>())), table_reference<Object>>);
-#endif
+    STATIC_REQUIRE(
+        storage_iterate_result_set<storage_type,
+                                   decltype(select(columns(object<Object>(), struct_<Object>(), 42))),
+                                   std::tuple<table_reference<Object>, structure<Object, std::tuple<>>, int>>);
 
 #if (SQLITE_VERSION_NUMBER >= 3008003) && defined(SQLITE_ORM_WITH_CTE)
 #ifdef SQLITE_ORM_WITH_CPP20_ALIASES