Added .is_null(), .is_not_null(), .like(), .not_like() (#14)

tests/sqlite/test_is_null.cpp

@@ -0,0 +1,54 @@
+
+#include <gtest/gtest.h>
+
+#include <rfl.hpp>
+#include <rfl/json.hpp>
+#include <sqlgen.hpp>
+#include <sqlgen/sqlite.hpp>
+#include <vector>
+
+namespace test_is_null {
+
+struct Person {
+  sqlgen::PrimaryKey<uint32_t> id;
+  std::string first_name;
+  std::string last_name;
+  std::optional<int> age;
+};
+
+TEST(sqlite, test_is_null) {
+  const auto people1 = std::vector<Person>(
+      {Person{.id = 0, .first_name = "Homer", .last_name = "Simpson"},
+       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"}});
+
+  using namespace sqlgen;
+
+  const auto conn = sqlite::connect();
+
+  const auto people2 =
+      conn.and_then(write(std::ref(people1)))
+          .and_then(sqlgen::read<std::vector<Person>> |
+                    where("age"_c.is_null()) | order_by("first_name"_c.desc()))
+          .value();
+
+  const auto people3 =
+      conn.and_then(sqlgen::read<std::vector<Person>> |
+                    where("age"_c.is_not_null()) | order_by("age"_c))
+          .value();
+
+  const std::string expected1 =
+      R"([{"id":4,"first_name":"Hugo","last_name":"Simpson"},{"id":0,"first_name":"Homer","last_name":"Simpson"}])";
+
+  const std::string expected2 =
+      R"([{"id":3,"first_name":"Maggie","last_name":"Simpson","age":0},{"id":2,"first_name":"Lisa","last_name":"Simpson","age":8},{"id":1,"first_name":"Bart","last_name":"Simpson","age":10}])";
+
+  EXPECT_EQ(rfl::json::write(people2), expected1);
+  EXPECT_EQ(rfl::json::write(people3), expected2);
+}
+
+}  // namespace test_is_null
+