Build fails: error: static_assert failed "could not find from_json() method in T's namespace"

[yurivict]

See the log here: http://beefy12.nyi.freebsd.org/data/head-amd64-default/p493484_s344398/logs/magnum-plugins-2019.01.log (IPv6 URL)

/wrkdirs/usr/ports/graphics/magnum-plugins/work/magnum-plugins-2019.01/src/MagnumExternal/TinyGltf/./json.hpp:1378:9: error: static_assert failed "could not find from_json() method in T's namespace"
        static_assert(sizeof(BasicJsonType) == 0,
        ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~
/wrkdirs/usr/ports/graphics/magnum-plugins/work/magnum-plugins-2019.01/src/MagnumExternal/TinyGltf/./json.hpp:1387:16: note: in instantiation of function template specialization 'nlohmann::detail::from_json_fn::call<nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::__1::basic_string_view<char, std::__1::char_traits<char> > >' requested here
        return call(j, val, priority_tag<1> {});
               ^
/wrkdirs/usr/ports/graphics/magnum-plugins/work/magnum-plugins-2019.01/src/MagnumExternal/TinyGltf/./json.hpp:6861:9: note: in instantiation of function template specialization 'nlohmann::detail::from_json_fn::operator()<nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, std::__1::basic_string_view<char, std::__1::char_traits<char> > >' requested here
        ::nlohmann::from_json(std::forward<BasicJsonType>(j), val);
        ^
/wrkdirs/usr/ports/graphics/magnum-plugins/work/magnum-plugins-2019.01/src/MagnumExternal/TinyGltf/./json.hpp:9578:36: note: in instantiation of function template specialization 'nlohmann::adl_serializer<std::__1::basic_string_view<char, std::__1::char_traits<char> >, void>::from_json<const nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer> &, std::__1::basic_string_view<char, std::__1::char_traits<char> > >' requested here
        JSONSerializer<ValueType>::from_json(*this, ret);
                                   ^
/wrkdirs/usr/ports/graphics/magnum-plugins/work/magnum-plugins-2019.01/src/MagnumExternal/TinyGltf/./json.hpp:9841:16: note: in instantiation of function template specialization 'nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>::get<std::__1::basic_string_view<char, std::__1::char_traits<char> >, std::__1::basic_string_view<char, std::__1::char_traits<char> >, 0>' requested here
        return get<ValueType>();
               ^
/usr/include/c++/v1/string:875:29: note: in instantiation of function template specialization 'nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>::operator basic_string_view<std::__1::basic_string_view<char, std::__1::char_traits<char> >, 0>' requested here
        {__self_view __sv = __t; return assign(__sv);}
                            ^
/wrkdirs/usr/ports/graphics/magnum-plugins/work/magnum-plugins-2019.01/src/MagnumExternal/TinyGltf/tiny_gltf.h:1924:12: note: in instantiation of function template specialization 'std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::operator=<nlohmann::basic_json<std::map, std::vector, std::__1::basic_string<char>, bool, long, unsigned long, double, std::allocator, adl_serializer>, void>' requested here
    (*ret) = it.value();

[mosra]

Huh. Neither my internet provider nor my mobile connection is IPv6-capable, apparently. That's sad. (Amended the issue to show the relevant portion, hope that's okay.)

As an aside: thank you for working on FreeBSD packages! 👍 💯

This is related to the external nlohmann/json library that TinyGltfImporter is using. I'm pinned to a quite ancient version there because the newer ones are way too huge and have terrible compile times (even this one is awful, but what can I do). Could you try swapping the json.hpp for a newer one and try building again? If that helps, maybe I could cherry-pick the change that fixes it (instead of doing a full upgrade).

I see it's using Clang and libc++, but don't see the version. What's the compiler version? Maybe I'll be able to reproduce here on ArchLinux as well.

Besides that, tiny_gltf might be going away from json.hpp in the future (a welcome change), so this issue might get solved by that as well. If the above doesn't help, I'm afraid you'll need to disable WITH_TINYGLTFIMPORTER for the time being.

[mosra]

Fixed by upgrading to json.hpp 3.3.0 in b64e5b3. Cherry-picking the change was impossible, so the code is inflated by another 200 kB :(