3 files changed, 25 insertions, 4 deletions

diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 9d869d513..65340d6ce 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -2319,11 +2319,30 @@ DrvOutputs LocalDerivationGoal::registerOutputs()
             buildUser ? std::optional(buildUser->getUIDRange()) : std::nullopt,
             inodesSeen);
 
-        debug("scanning for references for output '%s' in temp location '%s'", outputName, actualPath);
+        bool discardReferences = false;
+        if (auto structuredAttrs = parsedDrv->getStructuredAttrs()) {
+            if (auto outputChecks = get(*structuredAttrs, "outputChecks")) {
+                if (auto output = get(*outputChecks, outputName)) {
+                    if (auto unsafeDiscardReferences = get(*output, "unsafeDiscardReferences")) {
+                        settings.requireExperimentalFeature(Xp::DiscardReferences);
+                        if (!unsafeDiscardReferences->is_boolean())
+                            throw Error("attribute 'outputChecks.\"%s\".unsafeDiscardReferences' of derivation '%s' must be a Boolean", outputName, drvPath.to_string());
+                        discardReferences = unsafeDiscardReferences->get<bool>();
+                    }
+                }
+            }
+        }
 
-        /* Pass blank Sink as we are not ready to hash data at this stage. */
-        NullSink blank;
-        auto references = scanForReferences(blank, actualPath, referenceablePaths);
+        StorePathSet references;
+        if (discardReferences)
+            debug("discarding references of output '%s'", outputName);
+        else {
+            debug("scanning for references for output '%s' in temp location '%s'", outputName, actualPath);
+
+            /* Pass blank Sink as we are not ready to hash data at this stage. */
+            NullSink blank;
+            references = scanForReferences(blank, actualPath, referenceablePaths);
+        }
 
         outputReferencesIfUnregistered.insert_or_assign(
             outputName,
diff --git a/src/libutil/experimental-features.cc b/src/libutil/experimental-features.cc
index e0902971e..58d762ebb 100644
--- a/src/libutil/experimental-features.cc
+++ b/src/libutil/experimental-features.cc
@@ -16,6 +16,7 @@ std::map<ExperimentalFeature, std::string> stringifiedXpFeatures = {
     { Xp::ReplFlake, "repl-flake" },
     { Xp::AutoAllocateUids, "auto-allocate-uids" },
     { Xp::Cgroups, "cgroups" },
+    { Xp::DiscardReferences, "discard-references" },
 };
 
 const std::optional<ExperimentalFeature> parseExperimentalFeature(const std::string_view & name)
diff --git a/src/libutil/experimental-features.hh b/src/libutil/experimental-features.hh
index af775feb0..ac372e03e 100644
--- a/src/libutil/experimental-features.hh
+++ b/src/libutil/experimental-features.hh
@@ -25,6 +25,7 @@ enum struct ExperimentalFeature
     ReplFlake,
     AutoAllocateUids,
     Cgroups,
+    DiscardReferences,
 };
 
 /**