Added is_nullable

include/parsing/has_reflection_method.hpp

@@ -0,0 +1,15 @@
+#ifndef SQLGEN_PARSING_HAS_REFLECTION_TYPE_HPP_
+#define SQLGEN_PARSING_HAS_REFLECTION_TYPE_HPP_
+
+#include <concepts>
+
+namespace sqlgen::parsing {
+
+template <typename T>
+concept has_reflection_method = requires(T _t) {
+  { _t.reflection() } -> std::convertible_to<typename T::ReflectionType>;
+};
+
+}  // namespace sqlgen::parsing
+
+#endif

include/parsing/is_nullable.hpp

@@ -0,0 +1,38 @@
+#ifndef SQLGEN_PARSING_IS_NULLABLE_HPP_
+#define SQLGEN_PARSING_IS_NULLABLE_HPP_
+
+#include <memory>
+#include <optional>
+#include <type_traits>
+
+namespace sqlgen::parsing {
+
+/// Determines whether a field in a named tuple is required.
+/// General case - most fields are required.
+template <class T>
+class has_nullopt;
+
+template <class T>
+class has_nullopt : public std::false_type {};
+
+template <class T>
+class has_nullopt<std::optional<T>> : public std::true_type {};
+
+template <class T>
+class has_nullopt<std::shared_ptr<T>> : public std::true_type {};
+
+template <class T>
+class has_nullopt<std::unique_ptr<T>> : public std::true_type {};
+
+template <class T>
+consteval bool is_nullable() {
+  if constexpr (has_reflection_method<T>) {
+    return is_nullable<typename T::ReflectionType>();
+  } else {
+    return has_nullopt<T>::value;
+  }
+}
+
+}  // namespace sqlgen::parsing
+
+#endif