Made sure that setting to NULL values works

include/sqlgen/dynamic/Value.hpp

@@ -25,6 +25,8 @@ struct Integer {
   int64_t val;
 };
 
+struct Null {};
+
 struct String {
   std::string val;
 };
@@ -35,7 +37,7 @@ struct Timestamp {
 
 struct Value {
   using ReflectionType = rfl::TaggedUnion<"type", Duration, Boolean, Float,
-                                          Integer, String, Timestamp>;
+                                          Integer, Null, String, Timestamp>;
   const auto& reflection() const { return val; }
   ReflectionType val;
 };

include/sqlgen/transpilation/to_sets.hpp

@@ -31,10 +31,9 @@ struct ToSet<T, Set<transpilation::Col<_name>, ToType>> {
   static_assert(
       all_columns_exist<T, transpilation::Col<_name>>(),
       "At least one column referenced in your SET query does not exist.");
-  static_assert(
-      std::is_convertible_v<remove_nullable_t<underlying_t<T, Col<_name>>>,
-                            remove_nullable_t<underlying_t<T, Value<ToType>>>>,
-      "Must be convertible.");
+  static_assert(std::is_convertible_v<underlying_t<T, Value<ToType>>,
+                                      underlying_t<T, Col<_name>>>,
+                "Must be convertible.");
 
   dynamic::Update::Set operator()(const auto& _set) const {
     return dynamic::Update::Set{

include/sqlgen/transpilation/to_value.hpp

@@ -4,9 +4,11 @@
 #include <rfl.hpp>
 #include <type_traits>
 
+#include "../dynamic/Type.hpp"
 #include "../dynamic/Value.hpp"
 #include "Value.hpp"
 #include "has_reflection_method.hpp"
+#include "is_nullable.hpp"
 
 namespace sqlgen::transpilation {
 
@@ -17,7 +19,17 @@ template <class T>
 struct ToValue {
   dynamic::Value operator()(const T& _t) const {
     using Type = std::remove_cvref_t<T>;
-    if constexpr (std::is_floating_point_v<Type>) {
+    if constexpr (is_nullable_v<Type>) {
+      if (!_t) {
+        return dynamic::Value{dynamic::Null{}};
+      }
+      return ToValue<std::remove_cvref_t<decltype(*_t)>>{}(*_t);
+
+    } else if constexpr (std::is_same_v<Type, std::nullopt_t> ||
+                         std::is_same_v<Type, std::nullptr_t>) {
+      return dynamic::Value{dynamic::Null{}};
+
+    } else if constexpr (std::is_floating_point_v<Type>) {
       return dynamic::Value{dynamic::Float{.val = static_cast<double>(_t)}};
 
     } else if constexpr (std::is_same_v<Type, bool>) {

src/sqlgen/duckdb/to_sql.cpp

@@ -145,6 +145,9 @@ std::string column_or_value_to_sql(
       return "INTERVAL '" + std::to_string(_v.val) + " " +
              rfl::enum_to_string(_v.unit) + "'";
 
+    } else if constexpr (std::is_same_v<Type, dynamic::Null>) {
+      return "NULL";
+
     } else if constexpr (std::is_same_v<Type, dynamic::Timestamp>) {
       return "to_timestamp(" + std::to_string(_v.seconds_since_unix) + ")";
 

src/sqlgen/mysql/to_sql.cpp

@@ -175,6 +175,9 @@ std::string column_or_value_to_sql(
     if constexpr (std::is_same_v<Type, dynamic::String>) {
       return "'" + escape_single_quote(_v.val) + "'";
 
+    } else if constexpr (std::is_same_v<Type, dynamic::Null>) {
+      return "NULL";
+
     } else if constexpr (std::is_same_v<Type, dynamic::Duration>) {
       const auto unit =
           _v.unit == dynamic::TimeUnit::milliseconds

src/sqlgen/postgres/to_sql.cpp

@@ -134,6 +134,9 @@ std::string column_or_value_to_sql(
       return "INTERVAL '" + std::to_string(_v.val) + " " +
              rfl::enum_to_string(_v.unit) + "'";
 
+    } else if constexpr (std::is_same_v<Type, dynamic::Null>) {
+      return "NULL";
+
     } else if constexpr (std::is_same_v<Type, dynamic::Timestamp>) {
       return "to_timestamp(" + std::to_string(_v.seconds_since_unix) + ")";
 

src/sqlgen/sqlite/to_sql.cpp

@@ -136,6 +136,9 @@ std::string column_or_value_to_sql(
                  rfl::enum_to_string(_v.unit) + "'";
       }
 
+    } else if constexpr (std::is_same_v<Type, dynamic::Null>) {
+      return "NULL";
+
     } else if constexpr (std::is_same_v<Type, dynamic::Timestamp>) {
       return std::to_string(_v.seconds_since_unix);
 

tests/sqlite/test_update_with_optional.cpp

@@ -33,16 +33,22 @@ TEST(sqlite, test_update_with_optional) {
   using namespace sqlgen;
   using namespace sqlgen::literals;
 
-  const auto query =
-      update<Person>("first_name"_c.set("last_name"_c), "age"_c.set(100)) |
-      where("first_name"_c == "Hugo");
+  const auto query1 = update<Person>("first_name"_c.set("last_name"_c),
+                                     "age"_c.set(std::nullopt)) |
+                      where("first_name"_c == "Hugo");
 
-  query(conn).value();
+  const auto query2 =
+      update<Person>("age"_c.set(50)) | where("first_name"_c == "Homer");
+
+  const auto query3 = update<Person>("age"_c.set(std::optional<int>(11))) |
+                      where("first_name"_c == "Bart");
+
+  query1(conn).and_then(query2).and_then(query3).value();
 
   const auto people2 = sqlgen::read<std::vector<Person>>(conn).value();
 
   const std::string expected =
-      R"([{"id":0,"first_name":"Homer","last_name":"Simpson","age":45},{"id":1,"first_name":"Bart","last_name":"Simpson","age":10},{"id":2,"first_name":"Lisa","last_name":"Simpson","age":8},{"id":3,"first_name":"Maggie","last_name":"Simpson","age":0},{"id":4,"first_name":"Simpson","last_name":"Simpson","age":100}])";
+      R"([{"id":0,"first_name":"Homer","last_name":"Simpson","age":50},{"id":1,"first_name":"Bart","last_name":"Simpson","age":11},{"id":2,"first_name":"Lisa","last_name":"Simpson","age":8},{"id":3,"first_name":"Maggie","last_name":"Simpson","age":0},{"id":4,"first_name":"Simpson","last_name":"Simpson"}])";
 
   EXPECT_EQ(rfl::json::write(people2), expected);
 }