Expose an async interface for `queryRealisation`

Doesn’t change much so far because everything is still using it
synchronously, but should allow the binary cache to fetch stuff in
parallel

2 files changed, 5 insertions, 4 deletions

diff --git a/src/libstore/build/drv-output-substitution-goal.hh b/src/libstore/build/drv-output-substitution-goal.hh
index 63ab53d89..1b11a298e 100644
--- a/src/libstore/build/drv-output-substitution-goal.hh
+++ b/src/libstore/build/drv-output-substitution-goal.hh
@@ -20,7 +20,7 @@ private:
 
     // The realisation corresponding to the given output id.
     // Will be filled once we can get it.
-    std::optional<Realisation> outputInfo;
+    std::shared_ptr<const Realisation> outputInfo;
 
     /* The remaining substituters. */
     std::list<ref<Store>> subs;
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 2182f0bb4..b076bf998 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1224,13 +1224,14 @@ struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual Lo
     // corresponds to an allowed derivation
     { throw Error("registerDrvOutput"); }
 
-    std::optional<const Realisation> queryRealisation(const DrvOutput & id) override
+    void queryRealisationUncached(const DrvOutput & id,
+        Callback<std::shared_ptr<const Realisation>> callback) noexcept override
     // XXX: This should probably be allowed if the realisation corresponds to
     // an allowed derivation
     {
         if (!goal.isAllowed(id))
-            throw InvalidPath("cannot query an unknown output id '%s' in recursive Nix", id.to_string());
-        return next->queryRealisation(id);
+            callback(nullptr);
+        next->queryRealisation(id, std::move(callback));
     }
 
     void buildPaths(const std::vector<DerivedPath> & paths, BuildMode buildMode, std::shared_ptr<Store> evalStore) override