Alois Wohlschlager
21fc0ddce5
Currently, a bunch of documentation is generated by embedding parts of it in the nix executable, getting it out again by running it, and then postprocessing the output. This is bad, since it creates a pointless dependency of the documentation on the executable, and also makes documentation generation impossible when cross-compiling. Instead, both the code and the documentation should be generated from data, see https://git.lix.systems/lix-project/lix/issues/292 . Here we start applying this approach to the experimental and deprecated features, which are done in one go since the technical implementation is very similar. Of course, the actual benefits are not realised yet, since the offending pattern is used in several more places. These will be fixed later. Change-Id: I4c802052cc7e865c61119a34b8f1063c4decc9cb
109 lines
3.2 KiB
C++
109 lines
3.2 KiB
C++
#include "experimental-features.hh"
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// Required for instances of to_json and from_json for ExperimentalFeature
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#include "experimental-features-json.hh"
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#include "strings.hh"
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#include "nlohmann/json.hpp"
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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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nlohmann::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 (nlohmann::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(nlohmann::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 nlohmann::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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}
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