nix-super/src/libexpr/primops/fromTOML.cc

#include "primops.hh"
#include "eval-inline.hh"

#include "../../toml11/toml.hpp"

#include <sstream>

namespace nix {

static void prim_fromTOML(EvalState & state, const PosIdx pos, Value * * args, Value & val)
{
    auto toml = state.forceStringNoCtx(*args[0], pos, "while evaluating the argument passed to builtins.fromTOML");

    std::istringstream tomlStream(std::string{toml});

    std::function<void(Value &, toml::value)> visit;

    visit = [&](Value & v, toml::value t) {

        switch(t.type())
        {
            case toml::value_t::table:
                {
                    auto table = toml::get<toml::table>(t);

                    size_t size = 0;
                    for (auto & i : table) { (void) i; size++; }

                    auto attrs = state.buildBindings(size);

                    for(auto & elem : table)
                        visit(attrs.alloc(elem.first), elem.second);

                    v.mkAttrs(attrs);
                }
                break;;
            case toml::value_t::array:
                {
                    auto array = toml::get<std::vector<toml::value>>(t);

                    size_t size = array.size();
                    state.mkList(v, size);
                    for (size_t i = 0; i < size; ++i)
                        visit(*(v.listElems()[i] = state.allocValue()), array[i]);
                }
                break;;
            case toml::value_t::boolean:
                v.mkBool(toml::get<bool>(t));
                break;;
            case toml::value_t::integer:
                v.mkInt(toml::get<int64_t>(t));
                break;;
            case toml::value_t::floating:
                v.mkFloat(toml::get<NixFloat>(t));
                break;;
            case toml::value_t::string:
                v.mkString(toml::get<std::string>(t));
                break;;
            case toml::value_t::local_datetime:
            case toml::value_t::offset_datetime:
            case toml::value_t::local_date:
            case toml::value_t::local_time:
                {
                    if (experimentalFeatureSettings.isEnabled(Xp::ParseTomlTimestamps)) {
                        auto attrs = state.buildBindings(2);
                        attrs.alloc("_type").mkString("timestamp");
                        std::ostringstream s;
                        s << t;
                        attrs.alloc("value").mkString(s.str());
                        v.mkAttrs(attrs);
                    } else {
                        throw std::runtime_error("Dates and times are not supported");
                    }
                }
                break;;
            case toml::value_t::empty:
                v.mkNull();
                break;;

        }
    };

    try {
        visit(val, toml::parse(tomlStream, "fromTOML" /* the "filename" */));
    } catch (std::exception & e) { // TODO: toml::syntax_error
        throw EvalError({
            .msg = hintfmt("while parsing a TOML string: %s", e.what()),
            .errPos = state.positions[pos]
        });
    }
}

static RegisterPrimOp primop_fromTOML({
    .name = "fromTOML",
    .args = {"e"},
    .doc = R"(
      Convert a TOML string to a Nix value. For example,

      ```nix
      builtins.fromTOML ''
        x=1
        s="a"
        [table]
        y=2
      ''
      ```

      returns the value `{ s = "a"; table = { y = 2; }; x = 1; }`.
    )",
    .fun = prim_fromTOML
});

}