Guard the local overlay store behind an experimental feature

src/libstore/local-overlay-store.hh

@@ -56,6 +56,11 @@ struct LocalOverlayStoreConfig : virtual LocalStoreConfig
 
     const std::string name() override { return "Experimental Local Overlay Store"; }
 
+    std::optional<ExperimentalFeature> experimentalFeature() const override
+    {
+        return ExperimentalFeature::LocalOverlayStore;
+    }
+
     std::string doc() override
     {
         return

src/libstore/store-api.cc

@@ -1444,7 +1444,9 @@ std::shared_ptr<Store> openFromNonUri(const std::string & uri, const Store::Para
     } else if (uri == "local") {
         return std::make_shared<LocalStore>(params);
     } else if (uri == "local-overlay") {
-        return std::make_shared<LocalOverlayStore>(params);
+        auto store = std::make_shared<LocalOverlayStore>(params);
+        experimentalFeatureSettings.require(store->experimentalFeature());
+        return store;
     } else if (isNonUriPath(uri)) {
         Store::Params params2 = params;
         params2["root"] = absPath(uri);
@@ -1512,6 +1514,7 @@ ref<Store> openStore(const std::string & uri_,
         params.insert(uriParams.begin(), uriParams.end());
 
         if (auto store = openFromNonUri(uri, params)) {
+            experimentalFeatureSettings.require(store->experimentalFeature());
             store->warnUnknownSettings();
             return ref<Store>(store);
         }

src/libutil/experimental-features.cc

@@ -12,7 +12,7 @@ struct ExperimentalFeatureDetails
     std::string_view description;
 };
 
-constexpr std::array<ExperimentalFeatureDetails, 15> xpFeatureDetails = {{
+constexpr std::array<ExperimentalFeatureDetails, 16> xpFeatureDetails = {{
     {
         .tag = Xp::CaDerivations,
         .name = "ca-derivations",
@@ -228,6 +228,13 @@ constexpr std::array<ExperimentalFeatureDetails, 15> xpFeatureDetails = {{
             Allow the use of the `read-only` parameter in [local store](@docroot@/command-ref/new-cli/nix3-help-stores.md#local-store) URIs.
         )",
     },
+    {
+        .tag = Xp::LocalOverlayStore,
+        .name = "local-overlay-store",
+        .description = R"(
+            Allow the use of [local overlay store](@docroot@/command-ref/new-cli/nix3-help-stores.md#local-overlay-store).
+        )",
+    },
 }};
 
 static_assert(

src/libutil/experimental-features.hh

@@ -32,6 +32,7 @@ enum struct ExperimentalFeature
     DynamicDerivations,
     ParseTomlTimestamps,
     ReadOnlyLocalStore,
+    LocalOverlayStore,
 };
 
 /**

tests/overlay-local-store/common.sh

@@ -16,7 +16,7 @@ setupConfig () {
   addConfig "build-users-group = "
 }
 
-
+enableFeatures "local-overlay-store"
 
 storeDirs () {
   # Attempt to create store dirs on tmpfs volume.