Better support for nullable values in UPDATE...SET, resolves #108

docs/update.md

@@ -98,6 +98,37 @@ SET "first_name" = "last_name"
 WHERE "age" > 18;
 ```
 
+### Setting Nullable Values
+
+Columns can be set using std::optional<T> values. Passing std::nullopt will set the column to NULL in the database, and passing a std::optional<T> with a value will set the column to that value.
+
+```cpp
+using namespace sqlgen;
+using namespace sqlgen::literals;
+
+// set to NULL
+const auto query1 = update<Person>("age"_c.set(std::nullopt)) |
+                   where("first_name"_c == "Hugo");
+
+// set to a value
+const auto query2 = update<Person>("age"_c.set(std::optional<int>(11))) |
+                   where("first_name"_c == "Bart");
+
+query1(conn).and_then(query2).value();
+```
+
+This generates the following SQL:
+
+```sql
+UPDATE "Person"
+SET "age" = NULL
+WHERE "first_name" = 'Hugo';
+
+UPDATE "Person"
+SET "age" = 11
+WHERE "first_name" = 'Bart';
+```
+
 ## Example: Full Query Composition
 
 ```cpp

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

@@ -15,6 +15,7 @@
 #include "all_columns_exist.hpp"
 #include "get_schema.hpp"
 #include "get_tablename.hpp"
+#include "remove_nullable_t.hpp"
 #include "to_condition.hpp"
 #include "to_sets.hpp"
 #include "to_value.hpp"
@@ -30,8 +31,8 @@ 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<underlying_t<T, Col<_name>>,
-                                      underlying_t<T, Value<ToType>>>,
+  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 {

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/duckdb/test_update_with_optional.cpp

@@ -0,0 +1,57 @@
+#include <gtest/gtest.h>
+
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+#include <sqlgen.hpp>
+#include <sqlgen/duckdb.hpp>
+#include <vector>
+
+namespace test_update_with_optional {
+
+struct Person {
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::string first_name;
+  std::string last_name;
+  std::optional<int> age;
+};
+
+TEST(duckdb, test_update_with_optional) {
+  const auto people1 = std::vector<Person>(
+      {Person{
+           .id = 0, .first_name = "Homer", .last_name = "Simpson", .age = 45},
+       Person{.id = 1, .first_name = "Bart", .last_name = "Simpson", .age = 10},
+       Person{.id = 2, .first_name = "Lisa", .last_name = "Simpson", .age = 8},
+       Person{
+           .id = 3, .first_name = "Maggie", .last_name = "Simpson", .age = 0},
+       Person{
+           .id = 4, .first_name = "Hugo", .last_name = "Simpson", .age = 10}});
+
+  const auto conn = sqlgen::duckdb::connect();
+
+  sqlgen::write(conn, people1);
+
+  using namespace sqlgen;
+  using namespace sqlgen::literals;
+
+  const auto query1 = update<Person>("first_name"_c.set("last_name"_c),
+                                     "age"_c.set(std::nullopt)) |
+                      where("first_name"_c == "Hugo");
+
+  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>> | order_by("id"_c))(conn).value();
+
+  const std::string expected =
+      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);
+}
+
+}  // namespace test_update_with_optional

tests/mysql/test_update_with_optional.cpp

@@ -0,0 +1,67 @@
+#ifndef SQLGEN_BUILD_DRY_TESTS_ONLY
+
+#include <gtest/gtest.h>
+
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+#include <sqlgen.hpp>
+#include <sqlgen/mysql.hpp>
+#include <vector>
+
+namespace test_update_with_optional {
+
+struct Person {
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::string first_name;
+  std::string last_name;
+  std::optional<int> age;
+};
+
+TEST(mysql, test_update_with_optional) {
+  const auto people1 = std::vector<Person>(
+      {Person{
+           .id = 0, .first_name = "Homer", .last_name = "Simpson", .age = 45},
+       Person{.id = 1, .first_name = "Bart", .last_name = "Simpson", .age = 10},
+       Person{.id = 2, .first_name = "Lisa", .last_name = "Simpson", .age = 8},
+       Person{
+           .id = 3, .first_name = "Maggie", .last_name = "Simpson", .age = 0},
+       Person{
+           .id = 4, .first_name = "Hugo", .last_name = "Simpson", .age = 10}});
+
+  const auto credentials = sqlgen::mysql::Credentials{.host = "localhost",
+                                                      .user = "sqlgen",
+                                                      .password = "password",
+                                                      .dbname = "mysql"};
+
+  using namespace sqlgen;
+  using namespace sqlgen::literals;
+
+  const auto conn =
+      sqlgen::mysql::connect(credentials).and_then(drop<Person> | if_exists);
+
+  sqlgen::write(conn, people1);
+
+  const auto query1 = update<Person>("first_name"_c.set("last_name"_c),
+                                     "age"_c.set(std::nullopt)) |
+                      where("first_name"_c == "Hugo");
+
+  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>> | order_by("id"_c))(conn).value();
+
+  const std::string expected =
+      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);
+}
+
+}  // namespace test_update_with_optional
+
+#endif

tests/postgres/test_update_with_optional.cpp

@@ -0,0 +1,67 @@
+#ifndef SQLGEN_BUILD_DRY_TESTS_ONLY
+
+#include <gtest/gtest.h>
+
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+#include <sqlgen.hpp>
+#include <sqlgen/postgres.hpp>
+#include <vector>
+
+namespace test_update_with_optional {
+
+struct Person {
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::string first_name;
+  std::string last_name;
+  std::optional<int> age;
+};
+
+TEST(postgres, test_update_with_optional) {
+  const auto people1 = std::vector<Person>(
+      {Person{
+           .id = 0, .first_name = "Homer", .last_name = "Simpson", .age = 45},
+       Person{.id = 1, .first_name = "Bart", .last_name = "Simpson", .age = 10},
+       Person{.id = 2, .first_name = "Lisa", .last_name = "Simpson", .age = 8},
+       Person{
+           .id = 3, .first_name = "Maggie", .last_name = "Simpson", .age = 0},
+       Person{
+           .id = 4, .first_name = "Hugo", .last_name = "Simpson", .age = 10}});
+
+  const auto credentials = sqlgen::postgres::Credentials{.user = "postgres",
+                                                         .password = "password",
+                                                         .host = "localhost",
+                                                         .dbname = "postgres"};
+
+  using namespace sqlgen;
+  using namespace sqlgen::literals;
+
+  const auto conn =
+      sqlgen::postgres::connect(credentials).and_then(drop<Person> | if_exists);
+
+  sqlgen::write(conn, people1);
+
+  const auto query1 = update<Person>("first_name"_c.set("last_name"_c),
+                                     "age"_c.set(std::nullopt)) |
+                      where("first_name"_c == "Hugo");
+
+  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>> | order_by("id"_c))(conn).value();
+
+  const std::string expected =
+      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);
+}
+
+}  // namespace test_update_with_optional
+
+#endif

tests/sqlite/test_update_with_optional.cpp

@@ -0,0 +1,57 @@
+#include <gtest/gtest.h>
+
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+#include <sqlgen.hpp>
+#include <sqlgen/sqlite.hpp>
+#include <vector>
+
+namespace test_update_with_optional {
+
+struct Person {
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::string first_name;
+  std::string last_name;
+  std::optional<int> age;
+};
+
+TEST(sqlite, test_update_with_optional) {
+  const auto people1 = std::vector<Person>(
+      {Person{
+           .id = 0, .first_name = "Homer", .last_name = "Simpson", .age = 45},
+       Person{.id = 1, .first_name = "Bart", .last_name = "Simpson", .age = 10},
+       Person{.id = 2, .first_name = "Lisa", .last_name = "Simpson", .age = 8},
+       Person{
+           .id = 3, .first_name = "Maggie", .last_name = "Simpson", .age = 0},
+       Person{
+           .id = 4, .first_name = "Hugo", .last_name = "Simpson", .age = 10}});
+
+  const auto conn = sqlgen::sqlite::connect();
+
+  sqlgen::write(conn, people1);
+
+  using namespace sqlgen;
+  using namespace sqlgen::literals;
+
+  const auto query1 = update<Person>("first_name"_c.set("last_name"_c),
+                                     "age"_c.set(std::nullopt)) |
+                      where("first_name"_c == "Hugo");
+
+  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>> | order_by("id"_c))(conn).value();
+
+  const std::string expected =
+      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);
+}
+
+}  // namespace test_update_with_optional