Rework a few things with the experimental features list
- Use struct not `std::pair`, designated initializers - Use `constexpr` array that we can index by enum tag - It no longer segfaults; not sure why.
This commit is contained in:
John Ericson
parent
b2c9315bf2
commit
2585bcaa50
3 changed files with 142 additions and 82 deletions
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@ -5,75 +5,131 @@
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namespace nix {
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std::map<ExperimentalFeature, std::pair<std::string, std::string>> stringifiedXpFeatures = {
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{ Xp::CaDerivations, {"ca-derivations", R"(
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Allows derivations to be content-addressed in order to prevent rebuilds
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when changes to the derivation do not result in changes to the
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derivation's output. See
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[__contentAddressed](../language/advanced-attributes.md#adv-attr-__contentAddressed)
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for more info.
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)"} },
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{ Xp::ImpureDerivations, {"impure-derivations", R"(
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Allows derivations to produce non-fixed outputs by setting the `__impure`
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derivation attribute to `true`. See [these release
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notes](../release-notes/rl-2.8.md) for an example.
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)"} },
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{ Xp::Flakes, {"flakes", R"(
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Allows for derivations to be packaged in flakes. See the manual entry for
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[`nix flake`](../command-ref/new-cli/nix3-flake.md) or this [detailed
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introduction](https://www.tweag.io/blog/2020-05-25-flakes/) for more info.
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)"} },
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{ Xp::NixCommand, {"nix-command", R"(
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Allows the usage of the new `nix` CLI subcommands, such as `nix build`, `nix
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develop`, `nix run`, etc. See the manual for
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[`nix`](../command-ref/new-cli/nix.md) for more info.
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)"} },
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{ Xp::RecursiveNix, {"recursive-nix", R"(
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Allow Nix derivations to call Nix in order to recursively build derivations.
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See [this
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commit](https://github.com/edolstra/nix/commit/1a27aa7d64ffe6fc36cfca4d82bdf51c4d8cf717)
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for more info.
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)"} },
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{ Xp::NoUrlLiterals, {"no-url-literals", R"(
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Disallows unquoted URLs as part of the Nix language syntax. See [RFC
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45](https://github.com/NixOS/rfcs/pull/45) for more info.
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)"} },
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{ Xp::FetchClosure, {"fetch-closure", R"(
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Enables the use of the `fetchClosure` function in the standard library. See
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the docs for [`fetchClosure`](../language/builtins.md#builtins-fetchClosure)
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for more info.
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)"} },
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{ Xp::ReplFlake, {"repl-flake", R"(
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Allows the user to enter a Nix REPL within a flake, e.g. `nix repl nixpkgs`
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or `nix repl .#foo`.
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)"} },
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{ Xp::AutoAllocateUids, {"auto-allocate-uids", R"(
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Allows Nix to automatically pick UIDs for builds, rather than creating
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`nixbld*` user accounts. See [here](#conf-auto-allocate-uids) for more info.
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)"} },
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{ Xp::Cgroups, {"cgroups", R"(
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Allows Nix to execute builds inside cgroups. See
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[`use-cgroups`](#conf-use-cgroups) for more info.
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)"} },
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{ Xp::DiscardReferences, {"discard-references", R"(
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Enables the use of the `unsafeDiscardReferences` attribute in derivations
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that use structured attributes. This disables scanning of outputs for
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runtime dependencies.
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)"} },
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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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constexpr std::array<ExperimentalFeatureDetails, 11> xpFeatureDetails = {{
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{
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.tag = Xp::CaDerivations,
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.name = "ca-derivations",
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.description = R"(
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Allows derivations to be content-addressed in order to prevent rebuilds
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when changes to the derivation do not result in changes to the
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derivation's output. See
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[__contentAddressed](../language/advanced-attributes.md#adv-attr-__contentAddressed)
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for more info.
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)",
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},
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{
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.tag = Xp::ImpureDerivations,
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.name = "impure-derivations",
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.description = R"(
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Allows derivations to produce non-fixed outputs by setting the `__impure`
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derivation attribute to `true`. See [these release
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notes](../release-notes/rl-2.8.md) for an example.
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)",
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},
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{
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.tag = Xp::Flakes,
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.name = "flakes",
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.description = R"(
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Allows for derivations to be packaged in flakes. See the manual entry for
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[`nix flake`](../command-ref/new-cli/nix3-flake.md) or this [detailed
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introduction](https://www.tweag.io/blog/2020-05-25-flakes/) for more info.
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)",
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},
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{
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.tag = Xp::NixCommand,
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.name = "nix-command",
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.description = R"(
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Allows the usage of the new `nix` CLI subcommands, such as `nix build`, `nix
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develop`, `nix run`, etc. See the manual for
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[`nix`](../command-ref/new-cli/nix.md) for more info.
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)",
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},
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{
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.tag = Xp::RecursiveNix,
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.name = "recursive-nix",
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.description = R"(
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Allow Nix derivations to call Nix in order to recursively build derivations.
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See [this
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commit](https://github.com/edolstra/nix/commit/1a27aa7d64ffe6fc36cfca4d82bdf51c4d8cf717)
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for more info.
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)",
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},
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{
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.tag = Xp::NoUrlLiterals,
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.name = "no-url-literals",
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.description = R"(
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Disallows unquoted URLs as part of the Nix language syntax. See [RFC
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45](https://github.com/NixOS/rfcs/pull/45) for more info.
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)",
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},
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{
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.tag = Xp::FetchClosure,
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.name = "fetch-closure",
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.description = R"(
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Enables the use of the `fetchClosure` function in the standard library. See
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the docs for [`fetchClosure`](../language/builtins.md#builtins-fetchClosure)
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for more info.
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)",
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},
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{
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.tag = Xp::ReplFlake,
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.name = "repl-flake",
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.description = R"(
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Allows the user to enter a Nix REPL within a flake, e.g. `nix repl nixpkgs`
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or `nix repl .#foo`.
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)",
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},
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{
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.tag = Xp::AutoAllocateUids,
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.name = "auto-allocate-uids",
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.description = R"(
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Allows Nix to automatically pick UIDs for builds, rather than creating
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`nixbld*` user accounts. See [here](#conf-auto-allocate-uids) for more info.
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)",
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},
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{
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.tag = Xp::Cgroups,
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.name = "cgroups",
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.description = R"(
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Allows Nix to execute builds inside cgroups. See
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[`use-cgroups`](#conf-use-cgroups) for more info.
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)",
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},
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{
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.tag = Xp::DiscardReferences,
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.name = "discard-references",
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.description = R"(
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Enables the use of the `unsafeDiscardReferences` attribute in derivations
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that use structured attributes. This disables scanning of outputs for
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runtime dependencies.
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)",
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},
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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 auto reverseXpMap = []()
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{
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static std::unique_ptr<ReverseXpMap> reverseXpMap = [](){
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auto reverseXpMap = std::make_unique<ReverseXpMap>();
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std::string_view name;
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for (auto & [feature, featureStringPair] : stringifiedXpFeatures) {
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name = featureStringPair.first;
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(*reverseXpMap)[name] = feature;
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}
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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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@ -83,25 +139,29 @@ const std::optional<ExperimentalFeature> parseExperimentalFeature(const std::str
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return std::nullopt;
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}
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std::string_view showExperimentalFeature(const ExperimentalFeature feature)
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std::string_view showExperimentalFeature(const ExperimentalFeature tag)
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{
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const auto ret = get(stringifiedXpFeatures, feature);
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assert(ret);
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return ret->first;
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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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std::string getExperimentalFeaturesList() {
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std::string experimentalFeaturesList = R"(
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Experimental Nix features to enable.
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Current experimental features are the following:
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Experimental Nix features to enable.
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Current experimental features are the following:
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)";
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std::string experimentalFeatureString;
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for (auto& [feature, featureStringPair] : stringifiedXpFeatures) {
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experimentalFeatureString = " - `" + featureStringPair.first + "`\n";
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experimentalFeatureString += featureStringPair.second + "\n\n";
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experimentalFeaturesList += experimentalFeatureString;
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for (auto & xpFeature : xpFeatureDetails) {
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experimentalFeaturesList += std::string {}
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/* length of this first string must be 12, matching the indent of
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the descriptions in the xpFeatureDetails literal. FIXME compute
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markdown in a less hacky way. */
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+ " - "
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+ "`" + xpFeature.name + "`"
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+ "\n"
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+ xpFeature.description
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+ "\n\n";
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}
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return experimentalFeaturesList;
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@ -110,10 +170,9 @@ std::string getExperimentalFeaturesList() {
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std::set<ExperimentalFeature> parseFeatures(const std::set<std::string> & rawFeatures)
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{
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std::set<ExperimentalFeature> res;
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for (auto & rawFeature : rawFeatures) {
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for (auto & rawFeature : rawFeatures)
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if (auto feature = parseExperimentalFeature(rawFeature))
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res.insert(*feature);
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}
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return res;
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}
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@ -11,8 +11,9 @@ namespace nix {
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/**
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* The list of available experimental features.
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*
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* If you update this, don’t forget to also change the map defining their string
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* representation and documentation in the corresponding `.cc` file as well.
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* If you update this, don’t forget to also change the map defining
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* their string representation and documentation in the corresponding
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* `.cc` file as well.
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*/
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enum struct ExperimentalFeature
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{
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@ -730,16 +730,16 @@ constexpr auto enumerate(T && iterable)
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{
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size_t i;
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TIter iter;
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bool operator != (const iterator & other) const { return iter != other.iter; }
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void operator ++ () { ++i; ++iter; }
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auto operator * () const { return std::tie(i, *iter); }
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constexpr bool operator != (const iterator & other) const { return iter != other.iter; }
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constexpr void operator ++ () { ++i; ++iter; }
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constexpr auto operator * () const { return std::tie(i, *iter); }
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};
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struct iterable_wrapper
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{
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T iterable;
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auto begin() { return iterator{ 0, std::begin(iterable) }; }
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auto end() { return iterator{ 0, std::end(iterable) }; }
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constexpr auto begin() { return iterator{ 0, std::begin(iterable) }; }
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constexpr auto end() { return iterator{ 0, std::end(iterable) }; }
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};
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return iterable_wrapper{ std::forward<T>(iterable) };
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