#include <cassert>
#include <stdexcept>
#include <string>
#include <utility>
#include <vector>
class Config {
    std::vector<std::string> names_;
public:
    const std::vector<std::string>& names() const noexcept { return names_; }
    void replace(const std::vector<std::string>& input) {
        std::vector<std::string> candidate;
        candidate.reserve(input.size());
        for (const auto& name : input) {
            if (name.empty()) throw std::invalid_argument("empty name");
            candidate.push_back(name);
        }
        names_.swap(candidate);
    }
};
int main() {
    Config config;
    config.replace({"alpha", "beta"});
    const auto before = config.names();
    bool rejected = false;
    try { config.replace({"changed", ""}); }
    catch (const std::invalid_argument&) { rejected = true; }
    assert(rejected && config.names() == before);
    config.replace({});
    assert(config.names().empty());
}