Better support for nullable values in UPDATE...SET, resolves #108 (#111)

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