eldritch horrors
c3929c78f3
allow opting in to serialization as integers via a trait type instead, and add string-list serializers for the feature flag set enumerations. fixes #738 Change-Id: I2746eb5ef1f15c01b4e681f9ba1615b6c6e64f44
122 lines
3.4 KiB
C++
122 lines
3.4 KiB
C++
#include "lix/libutil/experimental-features.hh"
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#include "lix/libutil/json.hh"
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#include "lix/libutil/strings.hh"
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namespace nix {
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struct ExperimentalFeatureDetails
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{
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ExperimentalFeature tag;
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std::string_view name;
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std::string_view description;
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};
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/**
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* If two different PRs both add an experimental feature, and we just
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* used a number for this, we *woudln't* get merge conflict and the
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* counter will be incremented once instead of twice, causing a build
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* failure.
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*
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* By instead defining this instead as a dummy bottom experimental
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* feature, we do not get this issue.
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*/
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constexpr size_t numXpFeatures = static_cast<size_t>(Xp::NumXpFeatures);
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constexpr std::array<ExperimentalFeatureDetails, numXpFeatures> xpFeatureDetails = {{
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#include "experimental-features-impl.gen.inc"
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}};
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static_assert(
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[]() constexpr {
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for (auto [index, feature] : enumerate(xpFeatureDetails))
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if (index != (size_t)feature.tag)
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return false;
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return true;
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}(),
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"array order does not match enum tag order");
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const std::optional<ExperimentalFeature> parseExperimentalFeature(const std::string_view & name)
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{
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using ReverseXpMap = std::map<std::string_view, ExperimentalFeature>;
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static std::unique_ptr<ReverseXpMap> reverseXpMap = []() {
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auto reverseXpMap = std::make_unique<ReverseXpMap>();
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for (auto & xpFeature : xpFeatureDetails)
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(*reverseXpMap)[xpFeature.name] = xpFeature.tag;
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return reverseXpMap;
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}();
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if (auto feature = get(*reverseXpMap, name))
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return *feature;
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else
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return std::nullopt;
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}
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std::string_view showExperimentalFeature(const ExperimentalFeature tag)
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{
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assert((size_t)tag < xpFeatureDetails.size());
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return xpFeatureDetails[(size_t)tag].name;
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}
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JSON documentExperimentalFeatures()
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{
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StringMap res;
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for (auto & xpFeature : xpFeatureDetails)
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res[std::string { xpFeature.name }] =
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trim(stripIndentation(xpFeature.description));
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return (JSON) res;
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}
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ExperimentalFeatures parseFeatures(const std::set<std::string> & rawFeatures)
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{
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ExperimentalFeatures res {};
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for (auto & rawFeature : rawFeatures)
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if (auto feature = parseExperimentalFeature(rawFeature))
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res = res | *feature;
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return res;
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}
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MissingExperimentalFeature::MissingExperimentalFeature(ExperimentalFeature feature)
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: Error("experimental Lix feature '%1%' is disabled; use '--extra-experimental-features %1%' to override", showExperimentalFeature(feature))
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, missingFeature(feature)
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{}
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std::ostream & operator <<(std::ostream & str, const ExperimentalFeature & feature)
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{
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return str << showExperimentalFeature(feature);
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}
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void to_json(JSON & j, const ExperimentalFeature & feature)
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{
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j = showExperimentalFeature(feature);
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}
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void from_json(const JSON & j, ExperimentalFeature & feature)
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{
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const std::string input = j;
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const auto parsed = parseExperimentalFeature(input);
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if (parsed.has_value())
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feature = *parsed;
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else
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throw Error("Unknown experimental feature '%s' in JSON input", input);
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}
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void to_json(JSON & j, const ExperimentalFeatures & f)
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{
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StringSet res;
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for (auto & xpFeature : xpFeatureDetails) {
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if ((f & xpFeature.tag) == (ExperimentalFeatures{} | xpFeature.tag)) {
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res.emplace(xpFeature.name);
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}
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}
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j = res;
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}
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void from_json(const JSON & j, ExperimentalFeatures & f)
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{
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f = parseFeatures(j.get<StringSet>());
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}
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}
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