3 files changed, 35 insertions, 17 deletions

diff --git a/src/libfetchers/fetch-settings.hh b/src/libfetchers/fetch-settings.hh
index 7049dea30..4bc2d0e1a 100644
--- a/src/libfetchers/fetch-settings.hh
+++ b/src/libfetchers/fetch-settings.hh
@@ -75,21 +75,25 @@ struct FetchSettings : public Config
           Path or URI of the global flake registry.
 
           When empty, disables the global flake registry.
-        )"};
+        )",
+        {}, true, Xp::Flakes};
 
 
     Setting<bool> useRegistries{this, true, "use-registries",
-        "Whether to use flake registries to resolve flake references."};
+        "Whether to use flake registries to resolve flake references.",
+        {}, true, Xp::Flakes};
 
     Setting<bool> acceptFlakeConfig{this, false, "accept-flake-config",
-        "Whether to accept nix configuration from a flake without prompting."};
+        "Whether to accept nix configuration from a flake without prompting.",
+        {}, true, Xp::Flakes};
 
     Setting<std::string> commitLockFileSummary{
         this, "", "commit-lockfile-summary",
         R"(
           The commit summary to use when committing changed flake lock files. If
           empty, the summary is generated based on the action performed.
-        )"};
+        )",
+        {}, true, Xp::Flakes};
 };
 
 // FIXME: don't use a global variable.
diff --git a/src/libutil/config.cc b/src/libutil/config.cc
index 3b854eded..0dbb4de81 100644
--- a/src/libutil/config.cc
+++ b/src/libutil/config.cc
@@ -70,10 +70,17 @@ void AbstractConfig::reapplyUnknownSettings()
         set(s.first, s.second);
 }
 
+// Whether we should process the option. Excludes aliases, which are handled elsewhere, and disabled features.
+static bool applicable(const Config::SettingData & sd)
+{
+    return !sd.isAlias
+        && experimentalFeatureSettings.isEnabled(sd.setting->experimentalFeature);
+}
+
 void Config::getSettings(std::map<std::string, SettingInfo> & res, bool overriddenOnly)
 {
     for (auto & opt : _settings)
-        if (!opt.second.isAlias && (!overriddenOnly || opt.second.setting->overridden))
+        if (applicable(opt.second) && (!overriddenOnly || opt.second.setting->overridden))
             res.emplace(opt.first, SettingInfo{opt.second.setting->to_string(), opt.second.setting->description});
 }
 
@@ -147,9 +154,8 @@ nlohmann::json Config::toJSON()
 {
     auto res = nlohmann::json::object();
     for (auto & s : _settings)
-        if (!s.second.isAlias) {
+        if (applicable(s.second))
             res.emplace(s.first, s.second.setting->toJSON());
-        }
     return res;
 }
 
@@ -157,24 +163,27 @@ std::string Config::toKeyValue()
 {
     auto res = std::string();
     for (auto & s : _settings)
-        if (!s.second.isAlias) {
+        if (applicable(s.second))
             res += fmt("%s = %s\n", s.first, s.second.setting->to_string());
-        }
     return res;
 }
 
 void Config::convertToArgs(Args & args, const std::string & category)
 {
     for (auto & s : _settings)
-        if (!s.second.isAlias)
+        if (applicable(s.second))
             s.second.setting->convertToArg(args, category);
 }
 
 AbstractSetting::AbstractSetting(
     const std::string & name,
     const std::string & description,
-    const std::set<std::string> & aliases)
-    : name(name), description(stripIndentation(description)), aliases(aliases)
+    const std::set<std::string> & aliases,
+    std::optional<ExperimentalFeature> experimentalFeature)
+    : name(name)
+    , description(stripIndentation(description))
+    , aliases(aliases)
+    , experimentalFeature(experimentalFeature)
 {
 }
 
diff --git a/src/libutil/config.hh b/src/libutil/config.hh
index 3e6796f50..748d6043b 100644
--- a/src/libutil/config.hh
+++ b/src/libutil/config.hh
@@ -195,12 +195,15 @@ public:
 
     bool overridden = false;
 
+    std::optional<ExperimentalFeature> experimentalFeature;
+
 protected:
 
     AbstractSetting(
         const std::string & name,
         const std::string & description,
-        const std::set<std::string> & aliases);
+        const std::set<std::string> & aliases,
+        std::optional<ExperimentalFeature> experimentalFeature = std::nullopt);
 
     virtual ~AbstractSetting()
     {
@@ -241,8 +244,9 @@ public:
         const bool documentDefault,
         const std::string & name,
         const std::string & description,
-        const std::set<std::string> & aliases = {})
-        : AbstractSetting(name, description, aliases)
+        const std::set<std::string> & aliases = {},
+        std::optional<ExperimentalFeature> experimentalFeature = std::nullopt)
+        : AbstractSetting(name, description, aliases, experimentalFeature)
         , value(def)
         , defaultValue(def)
         , documentDefault(documentDefault)
@@ -297,8 +301,9 @@ public:
         const std::string & name,
         const std::string & description,
         const std::set<std::string> & aliases = {},
-        const bool documentDefault = true)
-        : BaseSetting<T>(def, documentDefault, name, description, aliases)
+        const bool documentDefault = true,
+        std::optional<ExperimentalFeature> experimentalFeature = std::nullopt)
+        : BaseSetting<T>(def, documentDefault, name, description, aliases, experimentalFeature)
     {
         options->addSetting(this);
     }