Changed NULL handling in results.

If the column or the connector indicates that NULL corresponds to a
trivial value, then the trivial value is returned. Otherwise, an
assert fails or an exception is thrown, depending on the preferences of
the connector.

include/sqlpp11/boolean.h

@@ -28,6 +28,7 @@
 #define SQLPP_BOOLEAN_H
 
 #include <cstdlib>
+#include <cassert>
 #include <ostream>
 #include <sqlpp11/basic_operators.h>
 #include <sqlpp11/type_traits.h>
@@ -98,7 +99,7 @@ namespace sqlpp
 				bool _is_null;
 			};
 
-			template<typename Db, bool TrivialIsNull = false>
+			template<typename Db, bool NullIsTrivial = false>
 			struct _result_entry_t
 			{
 				_result_entry_t():
@@ -134,15 +135,28 @@ namespace sqlpp
 
 				bool is_null() const
 			 	{ 
-					if (not _is_valid)
+					if (connector_assert_result_validity_t<Db>::value)
+						assert(_is_valid);
+					else if (not _is_valid)
 						throw exception("accessing is_null in non-existing row");
 					return _is_null; 
 				}
 
 				_cpp_value_type value() const
 				{
-					if (not _is_valid)
+					const bool null_value = _is_null and not NullIsTrivial and not connector_null_result_is_trivial_value_t<Db>::value;
-						throw exception("accessing value in non-existing row");
+					if (connector_assert_result_validity_t<Db>::value)
+					{
+						assert(_is_valid);
+						assert(not null_value);
+					}
+					else
+					{
+						if (not _is_valid)
+							throw exception("accessing value in non-existing row");
+						if (null_value)
+							throw exception("accessing value of NULL field");
+					}
 					return _value;
 				}
 

include/sqlpp11/floating_point.h

@@ -28,6 +28,7 @@
 #define SQLPP_FLOATING_POINT_H
 
 #include <cstdlib>
+#include <cassert>
 #include <sqlpp11/basic_operators.h>
 #include <sqlpp11/type_traits.h>
 #include <sqlpp11/exception.h>
@@ -98,7 +99,7 @@ namespace sqlpp
 				bool _is_null;
 			};
 
-			template<typename Db, bool TrivialIsNull = false>
+			template<typename Db, bool NullIsTrivial = false>
 			struct _result_entry_t
 			{
 				using _value_type = integral;
@@ -136,15 +137,28 @@ namespace sqlpp
 
 				bool is_null() const
 			 	{ 
-					if (not _is_valid)
+					if (connector_assert_result_validity_t<Db>::value)
+						assert(_is_valid);
+					else if (not _is_valid)
 						throw exception("accessing is_null in non-existing row");
 					return _is_null; 
 				}
 
 				_cpp_value_type value() const
 				{
-					if (not _is_valid)
+					const bool null_value = _is_null and not NullIsTrivial and not connector_null_result_is_trivial_value_t<Db>::value;
-						throw exception("accessing value in non-existing row");
+					if (connector_assert_result_validity_t<Db>::value)
+					{
+						assert(_is_valid);
+						assert(not null_value);
+					}
+					else
+					{
+						if (not _is_valid)
+							throw exception("accessing value in non-existing row");
+						if (null_value)
+							throw exception("accessing value of NULL field");
+					}
 					return _value;
 				}
 

include/sqlpp11/integral.h

@@ -28,6 +28,7 @@
 #define SQLPP_INTEGRAL_H
 
 #include <cstdlib>
+#include <cassert>
 #include <sqlpp11/basic_operators.h>
 #include <sqlpp11/type_traits.h>
 #include <sqlpp11/exception.h>
@@ -136,15 +137,28 @@ namespace sqlpp
 
 				bool is_null() const
 			 	{ 
-					if (not _is_valid)
+					if (connector_assert_result_validity_t<Db>::value)
+						assert(_is_valid);
+					else if (not _is_valid)
 						throw exception("accessing is_null in non-existing row");
 					return _is_null; 
 				}
 
 				_cpp_value_type value() const
 				{
-					if (not _is_valid)
+					const bool null_value = _is_null and not NullIsTrivial and not connector_null_result_is_trivial_value_t<Db>::value;
-						throw exception("accessing value in non-existing row");
+					if (connector_assert_result_validity_t<Db>::value)
+					{
+						assert(_is_valid);
+						assert(not null_value);
+					}
+					else
+					{
+						if (not _is_valid)
+							throw exception("accessing value in non-existing row");
+						if (null_value)
+							throw exception("accessing value of NULL field");
+					}
 					return _value;
 				}
 

include/sqlpp11/text.h

@@ -27,6 +27,7 @@
 #ifndef SQLPP_TEXT_H
 #define SQLPP_TEXT_H
 
+#include <cassert>
 #include <sqlpp11/basic_operators.h>
 #include <sqlpp11/type_traits.h>
 #include <sqlpp11/exception.h>
@@ -97,7 +98,7 @@ namespace sqlpp
 				bool _is_null;
 			};
 
-			template<typename Db, bool TrivialIsNull = false>
+			template<typename Db, bool NullIsTrivial = false>
 			struct _result_entry_t
 			{
 				_result_entry_t():
@@ -136,16 +137,29 @@ namespace sqlpp
 
 				bool is_null() const
 			 	{ 
-					if (not _is_valid)
+					if (connector_assert_result_validity_t<Db>::value)
+						assert(_is_valid);
+					else if (not _is_valid)
 						throw exception("accessing is_null in non-existing row");
 					return _value_ptr == nullptr; 
 				}
 
 				_cpp_value_type value() const
 				{
-					if (not _is_valid)
+					const bool null_value = _value_ptr == nullptr and not NullIsTrivial and not connector_null_result_is_trivial_value_t<Db>::value;
-						throw exception("accessing value in non-existing row");
+					if (connector_assert_result_validity_t<Db>::value)
-					if (_value_ptr)
+					{
+						assert(_is_valid);
+						assert(not null_value);
+					}
+					else
+					{
+						if (not _is_valid)
+							throw exception("accessing value in non-existing row");
+						if (null_value)
+							throw exception("accessing value of NULL field");
+					}
+					if (_value_ptr) 
 						return std::string(_value_ptr, _value_ptr + _len);
 					else
 						return "";

include/sqlpp11/type_traits.h

@@ -124,7 +124,8 @@ namespace sqlpp
 	SQLPP_TYPE_TRAIT_GENERATOR(requires_braces);
 	SQLPP_TYPE_TRAIT_GENERATOR(is_parameter);
 
-	SQLPP_CONNECTOR_TRAIT_GENERATOR(has_empty_list_insert);
+	SQLPP_CONNECTOR_TRAIT_GENERATOR(null_result_is_trivial_value);
+	SQLPP_CONNECTOR_TRAIT_GENERATOR(assert_result_validity);
 
 	template<typename T, template<typename> class IsTag>
 		using copy_type_trait = typename std::conditional<IsTag<T>::value, std::true_type, std::false_type>::type;