Merge remote-tracking branch 'origin/master' into overlayfs-store

src/libutil/experimental-features.cc

@@ -12,7 +12,7 @@ struct ExperimentalFeatureDetails
     std::string_view description;
 };
 
-constexpr std::array<ExperimentalFeatureDetails, 16> xpFeatureDetails = {{
+constexpr std::array<ExperimentalFeatureDetails, 15> xpFeatureDetails = {{
     {
         .tag = Xp::CaDerivations,
         .name = "ca-derivations",
@@ -182,15 +182,6 @@ constexpr std::array<ExperimentalFeatureDetails, 16> xpFeatureDetails = {{
             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.
-        )",
-    },
     {
         .tag = Xp::DaemonTrustOverride,
         .name = "daemon-trust-override",

src/libutil/experimental-features.hh

@@ -27,7 +27,6 @@ enum struct ExperimentalFeature
     ReplFlake,
     AutoAllocateUids,
     Cgroups,
-    DiscardReferences,
     DaemonTrustOverride,
     DynamicDerivations,
     ParseTomlTimestamps,

src/libutil/json-utils.cc

@@ -1,4 +1,5 @@
 #include "json-utils.hh"
+#include "error.hh"
 
 namespace nix {
 
@@ -16,4 +17,27 @@ nlohmann::json * get(nlohmann::json & map, const std::string & key)
     return &*i;
 }
 
+const nlohmann::json & valueAt(
+    const nlohmann::json & map,
+    const std::string & key)
+{
+    if (!map.contains(key))
+        throw Error("Expected JSON object to contain key '%s' but it doesn't", key);
+
+    return map[key];
+}
+
+const nlohmann::json & ensureType(
+    const nlohmann::json & value,
+    nlohmann::json::value_type expectedType
+    )
+{
+    if (value.type() != expectedType)
+        throw Error(
+            "Expected JSON value to be of type '%s' but it is of type '%s'",
+            nlohmann::json(expectedType).type_name(),
+            value.type_name());
+
+    return value;
+}
 }

src/libutil/json-utils.hh

@@ -10,6 +10,28 @@ const nlohmann::json * get(const nlohmann::json & map, const std::string & key);
 
 nlohmann::json * get(nlohmann::json & map, const std::string & key);
 
+/**
+ * Get the value of a json object at a key safely, failing
+ * with a Nix Error if the key does not exist.
+ *
+ * Use instead of nlohmann::json::at() to avoid ugly exceptions.
+ *
+ * _Does not check whether `map` is an object_, use `ensureType` for that.
+ */
+const nlohmann::json & valueAt(
+    const nlohmann::json & map,
+    const std::string & key);
+
+/**
+ * Ensure the type of a json object is what you expect, failing
+ * with a Nix Error if it isn't.
+ *
+ * Use before type conversions and element access to avoid ugly exceptions.
+ */
+const nlohmann::json & ensureType(
+    const nlohmann::json & value,
+    nlohmann::json::value_type expectedType);
+
 /**
  * For `adl_serializer<std::optional<T>>` below, we need to track what
  * types are not already using `null`. Only for them can we use `null`