nix/tests/unit/libutil/json-utils.cc

#include <vector>
#include <optional>

#include <gtest/gtest.h>

#include "json-utils.hh"

namespace nix {

/* Test `to_json` and `from_json` with `std::optional` types.
 * We are specifically interested in whether we can _nest_ optionals in STL
 * containers so we that we can leverage existing adl_serializer templates. */

TEST(to_json, optionalInt) {
    std::optional<int> val = std::make_optional(420);
    ASSERT_EQ(nlohmann::json(val), nlohmann::json(420));
    val = std::nullopt;
    ASSERT_EQ(nlohmann::json(val), nlohmann::json(nullptr));
}

TEST(to_json, vectorOfOptionalInts) {
    std::vector<std::optional<int>> vals = {
        std::make_optional(420),
        std::nullopt,
    };
    ASSERT_EQ(nlohmann::json(vals), nlohmann::json::parse("[420,null]"));
}

TEST(to_json, optionalVectorOfInts) {
    std::optional<std::vector<int>> val = std::make_optional(std::vector<int> {
        -420,
        420,
    });
    ASSERT_EQ(nlohmann::json(val), nlohmann::json::parse("[-420,420]"));
    val = std::nullopt;
    ASSERT_EQ(nlohmann::json(val), nlohmann::json(nullptr));
}

TEST(from_json, optionalInt) {
    nlohmann::json json = 420;
    std::optional<int> val = json;
    ASSERT_TRUE(val.has_value());
    ASSERT_EQ(*val, 420);
    json = nullptr;
    json.get_to(val);
    ASSERT_FALSE(val.has_value());
}

TEST(from_json, vectorOfOptionalInts) {
    nlohmann::json json = { 420, nullptr };
    std::vector<std::optional<int>> vals = json;
    ASSERT_EQ(vals.size(), 2);
    ASSERT_TRUE(vals.at(0).has_value());
    ASSERT_EQ(*vals.at(0), 420);
    ASSERT_FALSE(vals.at(1).has_value());
}

} /* namespace nix */