Shouldn't nlohmann::basic_json::contains be decorated with "noexcept" if it does not throw exception for 1) and 2) overloads?

[TrueWodzu]

Hi,

Basically the title says all. Documentation states that for first and second overloads of contains function:

// (1)
bool contains(const typename object_t::key_type& key) const;

// (2)
template<typename KeyType>
bool contains(KeyType&& key) const;

// (3)
bool contains(const json_pointer& ptr) const;

they do not throw, but they are not marked with noexcept, why?

[TrueWodzu]

Just checked example from the documentation:

#include <iostream>
#include <nlohmann/json.hpp>

using json = nlohmann::json;
using namespace nlohmann::literals;

int main()
{
    // create a JSON value
    json j =
    {
        {"number", 1}, {"string", "foo"}, {"array", {1, 2}}
    };

    std::cout << std::boolalpha
              << j.contains("/number"_json_pointer) << '\n'
              << j.contains("/string"_json_pointer) << '\n'
              << j.contains("/array"_json_pointer) << '\n'
              << j.contains("/array/1"_json_pointer) << '\n'
              << j.contains("/array/-"_json_pointer) << '\n'
              << j.contains("/array/4"_json_pointer) << '\n'
              << j.contains("/baz"_json_pointer) << std::endl;

    try
    {
        // try to use an array index with leading '0'
        j.contains("/array/01"_json_pointer);
    }
    catch (json::parse_error& e)
    {
        std::cout << e.what() << '\n';
    }

    try
    {
        // try to use an array index that is not a number
        j.contains("/array/one"_json_pointer);
    }
    catch (json::parse_error& e)
    {
        std::cout << e.what() << '\n';
    }
}

For the last two use cases exceptions are not thrown but according to example they should.

[gregmarr]

The first two overloads call m_data.m_value.object->find(), and std::map::find() is not noexcept. Also, std::map is only the default type, it can be replaced by the user. It could be conditionally noexcept if object->find() is noexcept but that would not have any real effect due to the default being not noexcept.