diff options
| -rw-r--r-- | .gitignore | 2 | ||||
| -rw-r--r-- | doc/manual/generate-xp-features.nix | 11 | ||||
| -rw-r--r-- | doc/manual/local.mk | 13 | ||||
| -rw-r--r-- | doc/manual/utils.nix | 6 | ||||
| -rw-r--r-- | src/libutil/config.hh | 17 | ||||
| -rw-r--r-- | src/libutil/experimental-features.cc | 230 | ||||
| -rw-r--r-- | src/libutil/experimental-features.hh | 37 | ||||
| -rw-r--r-- | src/libutil/util.hh | 10 | ||||
| -rw-r--r-- | src/nix/main.cc | 5 |
9 files changed, 292 insertions, 39 deletions
diff --git a/.gitignore b/.gitignore index e326966d6..53442751f 100644 --- a/.gitignore +++ b/.gitignore @@ -19,9 +19,11 @@ perl/Makefile.config /doc/manual/nix.json /doc/manual/conf-file.json /doc/manual/builtins.json +/doc/manual/xp-features.json /doc/manual/src/SUMMARY.md /doc/manual/src/command-ref/new-cli /doc/manual/src/command-ref/conf-file.md +/doc/manual/src/command-ref/experimental-features.md /doc/manual/src/language/builtins.md # /scripts/ diff --git a/doc/manual/generate-xp-features.nix b/doc/manual/generate-xp-features.nix new file mode 100644 index 000000000..db1ba6092 --- /dev/null +++ b/doc/manual/generate-xp-features.nix @@ -0,0 +1,11 @@ +with builtins; +with import ./utils.nix; + +let + showExperimentalFeature = name: doc: + squash '' + - <span id="xp-feature-${name}">[`${name}`](#xp-feature-${name})</span> + + ${indent " " doc} + ''; +in xps: indent " " (concatStringsSep "\n" (attrValues (mapAttrs showExperimentalFeature xps))) diff --git a/doc/manual/local.mk b/doc/manual/local.mk index df941d460..0d4b9d640 100644 --- a/doc/manual/local.mk +++ b/doc/manual/local.mk @@ -88,12 +88,12 @@ $(d)/src/SUMMARY.md: $(d)/src/SUMMARY.md.in $(d)/src/command-ref/new-cli @cp $< $@ @$(call process-includes,$@,$@) -$(d)/src/command-ref/new-cli: $(d)/nix.json $(d)/generate-manpage.nix $(bindir)/nix +$(d)/src/command-ref/new-cli: $(d)/nix.json $(d)/utils.nix $(d)/generate-manpage.nix $(bindir)/nix @rm -rf $@ $@.tmp $(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-manpage.nix (builtins.readFile $<)' @mv $@.tmp $@ -$(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/utils.nix $(d)/src/command-ref/conf-file-prefix.md $(bindir)/nix +$(d)/src/command-ref/conf-file.md: $(d)/conf-file.json $(d)/utils.nix $(d)/src/command-ref/conf-file-prefix.md $(d)/src/command-ref/experimental-features.md $(bindir)/nix @cat doc/manual/src/command-ref/conf-file-prefix.md > $@.tmp $(trace-gen) $(nix-eval) --expr '(import doc/manual/utils.nix).showSettings { useAnchors = true; } (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp; @mv $@.tmp $@ @@ -106,6 +106,15 @@ $(d)/conf-file.json: $(bindir)/nix $(trace-gen) $(dummy-env) $(bindir)/nix show-config --json --experimental-features nix-command > $@.tmp @mv $@.tmp $@ +$(d)/src/command-ref/experimental-features.md: $(d)/xp-features.json $(d)/utils.nix $(d)/generate-xp-features.nix $(bindir)/nix + @rm -rf $@ $@.tmp + $(trace-gen) $(nix-eval) --write-to $@.tmp --expr 'import doc/manual/generate-xp-features.nix (builtins.fromJSON (builtins.readFile $<))' + @mv $@.tmp $@ + +$(d)/xp-features.json: $(bindir)/nix + $(trace-gen) $(dummy-env) NIX_PATH=nix/corepkgs=corepkgs $(bindir)/nix __dump-xp-features > $@.tmp + @mv $@.tmp $@ + $(d)/src/language/builtins.md: $(d)/builtins.json $(d)/generate-builtins.nix $(d)/src/language/builtins-prefix.md $(bindir)/nix @cat doc/manual/src/language/builtins-prefix.md > $@.tmp $(trace-gen) $(nix-eval) --expr 'import doc/manual/generate-builtins.nix (builtins.fromJSON (builtins.readFile $<))' >> $@.tmp; diff --git a/doc/manual/utils.nix b/doc/manual/utils.nix index 5eacce0dd..f78e6bb02 100644 --- a/doc/manual/utils.nix +++ b/doc/manual/utils.nix @@ -74,10 +74,10 @@ rec { if aliases == [] then "" else "**Deprecated alias:** ${(concatStringsSep ", " (map (s: "`${s}`") aliases))}"; - indent = prefix: s: - concatStringsSep "\n" (map (x: if x == "" then x else "${prefix}${x}") (splitLines s)); - in result; + indent = prefix: s: + concatStringsSep "\n" (map (x: if x == "" then x else "${prefix}${x}") (splitLines s)); + showSettings = args: settingsInfo: concatStrings (attrValues (mapAttrs (showSetting args) settingsInfo)); } diff --git a/src/libutil/config.hh b/src/libutil/config.hh index 3c1d70294..8b0fe6555 100644 --- a/src/libutil/config.hh +++ b/src/libutil/config.hh @@ -371,8 +371,21 @@ extern GlobalConfig globalConfig; struct ExperimentalFeatureSettings : Config { - Setting<std::set<ExperimentalFeature>> experimentalFeatures{this, {}, "experimental-features", - "Experimental Nix features to enable."}; + Setting<std::set<ExperimentalFeature>> experimentalFeatures{ + this, {}, "experimental-features", + R"( + Experimental features that are enabled. + + Example: + + ``` + experimental-features = nix-command flakes + ``` + + Experimental features available: + + {{#include experimental-features.md}} + )"}; /** * Check whether the given experimental feature is enabled. diff --git a/src/libutil/experimental-features.cc b/src/libutil/experimental-features.cc index 58d762ebb..aa3367639 100644 --- a/src/libutil/experimental-features.cc +++ b/src/libutil/experimental-features.cc @@ -5,29 +5,209 @@ namespace nix { -std::map<ExperimentalFeature, std::string> stringifiedXpFeatures = { - { Xp::CaDerivations, "ca-derivations" }, - { Xp::ImpureDerivations, "impure-derivations" }, - { Xp::Flakes, "flakes" }, - { Xp::NixCommand, "nix-command" }, - { Xp::RecursiveNix, "recursive-nix" }, - { Xp::NoUrlLiterals, "no-url-literals" }, - { Xp::FetchClosure, "fetch-closure" }, - { Xp::ReplFlake, "repl-flake" }, - { Xp::AutoAllocateUids, "auto-allocate-uids" }, - { Xp::Cgroups, "cgroups" }, - { Xp::DiscardReferences, "discard-references" }, +struct ExperimentalFeatureDetails +{ + ExperimentalFeature tag; + std::string_view name; + std::string_view description; }; +constexpr std::array<ExperimentalFeatureDetails, 11> xpFeatureDetails = {{ + { + .tag = Xp::CaDerivations, + .name = "ca-derivations", + .description = R"( + Allow derivations to be content-addressed in order to prevent + rebuilds when changes to the derivation do not result in changes to + the derivation's output. See + [__contentAddressed](@docroot@/language/advanced-attributes.md#adv-attr-__contentAddressed) + for details. + )", + }, + { + .tag = Xp::ImpureDerivations, + .name = "impure-derivations", + .description = R"( + Allow derivations to produce non-fixed outputs by setting the + `__impure` derivation attribute to `true`. An impure derivation can + have differing outputs each time it is built. + + Example: + + ``` + derivation { + name = "impure"; + builder = /bin/sh; + __impure = true; # mark this derivation as impure + args = [ "-c" "read -n 10 random < /dev/random; echo $random > $out" ]; + system = builtins.currentSystem; + } + ``` + + Each time this derivation is built, it can produce a different + output (as the builder outputs random bytes to `$out`). Impure + derivations also have access to the network, and only fixed-output + or other impure derivations can rely on impure derivations. Finally, + an impure derivation cannot also be + [content-addressed](#xp-feature-ca-derivations). + )", + }, + { + .tag = Xp::Flakes, + .name = "flakes", + .description = R"( + Enable flakes. See the manual entry for [`nix + flake`](../command-ref/new-cli/nix3-flake.md) for details. + )", + }, + { + .tag = Xp::NixCommand, + .name = "nix-command", + .description = R"( + Enable the new `nix` subcommands. See the manual on + [`nix`](@docroot@/command-ref/new-cli/nix.md) for details. + )", + }, + { + .tag = Xp::RecursiveNix, + .name = "recursive-nix", + .description = R"( + Allow derivation builders to call Nix, and thus build derivations + recursively. + + Example: + + ``` + with import <nixpkgs> {}; + + runCommand "foo" + { + buildInputs = [ nix jq ]; + NIX_PATH = "nixpkgs=${<nixpkgs>}"; + } + '' + hello=$(nix-build -E '(import <nixpkgs> {}).hello.overrideDerivation (args: { name = "recursive-hello"; })') + + mkdir -p $out/bin + ln -s $hello/bin/hello $out/bin/hello + '' + ``` + + An important restriction on recursive builders is disallowing + arbitrary substitutions. For example, running + + ``` + nix-store -r /nix/store/kmwd1hq55akdb9sc7l3finr175dajlby-hello-2.10 + ``` + + in the above `runCommand` script would be disallowed, as this could + lead to derivations with hidden dependencies or breaking + reproducibility by relying on the current state of the Nix store. An + exception would be if + `/nix/store/kmwd1hq55akdb9sc7l3finr175dajlby-hello-2.10` were + already in the build inputs or built by a previous recursive Nix + call. + )", + }, + { + .tag = Xp::NoUrlLiterals, + .name = "no-url-literals", + .description = R"( + Disallow unquoted URLs as part of the Nix language syntax. The Nix + language allows for URL literals, like so: + + ``` + $ nix repl + Welcome to Nix 2.15.0. Type :? for help. + + nix-repl> http://foo + "http://foo" + ``` + + But enabling this experimental feature will cause the Nix parser to + throw an error when encountering a URL literal: + + ``` + $ nix repl --extra-experimental-features 'no-url-literals' + Welcome to Nix 2.15.0. Type :? for help. + + nix-repl> http://foo + error: URL literals are disabled + + at «string»:1:1: + + 1| http://foo + | ^ + + ``` + + While this is currently an experimental feature, unquoted URLs are + being deprecated and their usage is discouraged. + + The reason is that, as opposed to path literals, URLs have no + special properties that distinguish them from regular strings, URLs + containing parameters have to be quoted anyway, and unquoted URLs + may confuse external tooling. + )", + }, + { + .tag = Xp::FetchClosure, + .name = "fetch-closure", + .description = R"( + Enable the use of the [`fetchClosure`](@docroot@/language/builtins.md#builtins-fetchClosure) built-in function in the Nix language. + )", + }, + { + .tag = Xp::ReplFlake, + .name = "repl-flake", + .description = R"( + Allow passing [installables](@docroot@/command-ref/new-cli/nix.md#installables) to `nix repl`, making its interface consistent with the other experimental commands. + )", + }, + { + .tag = Xp::AutoAllocateUids, + .name = "auto-allocate-uids", + .description = R"( + Allows Nix to automatically pick UIDs for builds, rather than creating + `nixbld*` user accounts. See the [`auto-allocate-uids`](#conf-auto-allocate-uids) setting for details. + )", + }, + { + .tag = Xp::Cgroups, + .name = "cgroups", + .description = R"( + Allows Nix to execute builds inside cgroups. See + the [`use-cgroups`](#conf-use-cgroups) setting for details. + )", + }, + { + .tag = Xp::DiscardReferences, + .name = "discard-references", + .description = R"( + Allow the use of the [`unsafeDiscardReferences`](@docroot@/language/advanced-attributes.html#adv-attr-unsafeDiscardReferences) attribute in derivations + that use [structured attributes](@docroot@/language/advanced-attributes.html#adv-attr-structuredAttrs). This disables scanning of outputs for + runtime dependencies. + )", + }, +}}; + +static_assert( + []() constexpr { + for (auto [index, feature] : enumerate(xpFeatureDetails)) + if (index != (size_t)feature.tag) + return false; + return true; + }(), + "array order does not match enum tag order"); + const std::optional<ExperimentalFeature> parseExperimentalFeature(const std::string_view & name) { using ReverseXpMap = std::map<std::string_view, ExperimentalFeature>; - static auto reverseXpMap = []() - { + static std::unique_ptr<ReverseXpMap> reverseXpMap = [](){ auto reverseXpMap = std::make_unique<ReverseXpMap>(); - for (auto & [feature, name] : stringifiedXpFeatures) - (*reverseXpMap)[name] = feature; + for (auto & xpFeature : xpFeatureDetails) + (*reverseXpMap)[xpFeature.name] = xpFeature.tag; return reverseXpMap; }(); @@ -37,20 +217,26 @@ const std::optional<ExperimentalFeature> parseExperimentalFeature(const std::str return std::nullopt; } -std::string_view showExperimentalFeature(const ExperimentalFeature feature) +std::string_view showExperimentalFeature(const ExperimentalFeature tag) { - const auto ret = get(stringifiedXpFeatures, feature); - assert(ret); - return *ret; + assert((size_t)tag < xpFeatureDetails.size()); + return xpFeatureDetails[(size_t)tag].name; +} + +nlohmann::json documentExperimentalFeatures() { + StringMap res; + for (auto & xpFeature : xpFeatureDetails) + res[std::string { xpFeature.name }] = + trim(stripIndentation(xpFeature.description)); + return (nlohmann::json) res; } std::set<ExperimentalFeature> parseFeatures(const std::set<std::string> & rawFeatures) { std::set<ExperimentalFeature> res; - for (auto & rawFeature : rawFeatures) { + for (auto & rawFeature : rawFeatures) if (auto feature = parseExperimentalFeature(rawFeature)) res.insert(*feature); - } return res; } diff --git a/src/libutil/experimental-features.hh b/src/libutil/experimental-features.hh index 5948ad7ad..8ef66263a 100644 --- a/src/libutil/experimental-features.hh +++ b/src/libutil/experimental-features.hh @@ -11,8 +11,9 @@ namespace nix { /** * The list of available experimental features. * - * If you update this, don’t forget to also change the map defining their - * string representation in the corresponding `.cc` file. + * If you update this, don’t forget to also change the map defining + * their string representation and documentation in the corresponding + * `.cc` file as well. */ enum struct ExperimentalFeature { @@ -34,26 +35,52 @@ enum struct ExperimentalFeature */ using Xp = ExperimentalFeature; +/** + * Parse an experimental feature (enum value) from its name. Experimental + * feature flag names are hyphenated and do not contain spaces. + */ const std::optional<ExperimentalFeature> parseExperimentalFeature( const std::string_view & name); + +/** + * Show the name of an experimental feature. This is the opposite of + * parseExperimentalFeature(). + */ std::string_view showExperimentalFeature(const ExperimentalFeature); +/** + * Compute the documentation of all experimental features. + * + * See `doc/manual` for how this information is used. + */ +nlohmann::json documentExperimentalFeatures(); + +/** + * Shorthand for `str << showExperimentalFeature(feature)`. + */ std::ostream & operator<<( std::ostream & str, const ExperimentalFeature & feature); /** - * Parse a set of strings to the corresponding set of experimental features, - * ignoring (but warning for) any unkwown feature. + * Parse a set of strings to the corresponding set of experimental + * features, ignoring (but warning for) any unknown feature. */ std::set<ExperimentalFeature> parseFeatures(const std::set<std::string> &); +/** + * An experimental feature was required for some (experimental) + * operation, but was not enabled. + */ class MissingExperimentalFeature : public Error { public: + /** + * The experimental feature that was required but not enabled. + */ ExperimentalFeature missingFeature; - MissingExperimentalFeature(ExperimentalFeature); + MissingExperimentalFeature(ExperimentalFeature missingFeature); }; /** diff --git a/src/libutil/util.hh b/src/libutil/util.hh index 6c2706cc1..94c9efb74 100644 --- a/src/libutil/util.hh +++ b/src/libutil/util.hh @@ -730,16 +730,16 @@ constexpr auto enumerate(T && iterable) { size_t i; TIter iter; - bool operator != (const iterator & other) const { return iter != other.iter; } - void operator ++ () { ++i; ++iter; } - auto operator * () const { return std::tie(i, *iter); } + constexpr bool operator != (const iterator & other) const { return iter != other.iter; } + constexpr void operator ++ () { ++i; ++iter; } + constexpr auto operator * () const { return std::tie(i, *iter); } }; struct iterable_wrapper { T iterable; - auto begin() { return iterator{ 0, std::begin(iterable) }; } - auto end() { return iterator{ 0, std::end(iterable) }; } + constexpr auto begin() { return iterator{ 0, std::begin(iterable) }; } + constexpr auto end() { return iterator{ 0, std::end(iterable) }; } }; return iterable_wrapper{ std::forward<T>(iterable) }; diff --git a/src/nix/main.cc b/src/nix/main.cc index 4d4164333..62b1f98d1 100644 --- a/src/nix/main.cc +++ b/src/nix/main.cc @@ -374,6 +374,11 @@ void mainWrapped(int argc, char * * argv) return; } + if (argc == 2 && std::string(argv[1]) == "__dump-xp-features") { + logger->cout(documentExperimentalFeatures().dump()); + return; + } + Finally printCompletions([&]() { if (completions) { |