From 296831f641b2ce43f179ec710c3ef76726ef96e2 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Fri, 17 Mar 2023 10:33:48 -0400
Subject: Move enabled experimental feature to libutil struct

This is needed in subsequent commits to allow the settings and CLI args
infrastructure itself to read this setting.
---
 src/libutil/config.hh | 40 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 37 insertions(+), 3 deletions(-)

(limited to 'src/libutil/config.hh')

diff --git a/src/libutil/config.hh b/src/libutil/config.hh
index 7ac43c854..3e6796f50 100644
--- a/src/libutil/config.hh
+++ b/src/libutil/config.hh
@@ -1,12 +1,13 @@
+#pragma once
+
 #include <cassert>
 #include <map>
 #include <set>
 
-#include "types.hh"
-
 #include <nlohmann/json_fwd.hpp>
 
-#pragma once
+#include "types.hh"
+#include "experimental-features.hh"
 
 namespace nix {
 
@@ -357,4 +358,37 @@ struct GlobalConfig : public AbstractConfig
 
 extern GlobalConfig globalConfig;
 
+
+struct ExperimentalFeatureSettings : Config {
+
+    Setting<std::set<ExperimentalFeature>> experimentalFeatures{this, {}, "experimental-features",
+        "Experimental Nix features to enable."};
+
+    /**
+     * Check whether the given experimental feature is enabled.
+     */
+    bool isEnabled(const ExperimentalFeature &) const;
+
+    /**
+     * Require an experimental feature be enabled, throwing an error if it is
+     * not.
+     */
+    void require(const ExperimentalFeature &) const;
+
+    /**
+     * `std::nullopt` pointer means no feature, which means there is nothing that could be
+     * disabled, and so the function returns true in that case.
+     */
+    bool isEnabled(const std::optional<ExperimentalFeature> &) const;
+
+    /**
+     * `std::nullopt` pointer means no feature, which means there is nothing that could be
+     * disabled, and so the function does nothing in that case.
+     */
+    void require(const std::optional<ExperimentalFeature> &) const;
+};
+
+// FIXME: don't use a global variable.
+extern ExperimentalFeatureSettings experimentalFeatureSettings;
+
 }
-- 
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