libstore: de-callback-ify Store::queryRealisation

Change-Id: I8d74745c519518f163f51dfaa39063836f17599e

src/libstore/store-api.cc

@@ -716,34 +716,26 @@ ref<const ValidPathInfo> Store::queryPathInfo(const StorePath & storePath)
     return ref<const ValidPathInfo>(info);
 }
 
-void Store::queryRealisation(const DrvOutput & id,
+std::shared_ptr<const Realisation> Store::queryRealisation(const DrvOutput & id)
-        Callback<std::shared_ptr<const Realisation>> callback) noexcept
 {
 
-    try {
     if (diskCache) {
         auto [cacheOutcome, maybeCachedRealisation]
             = diskCache->lookupRealisation(getUri(), id);
         switch (cacheOutcome) {
         case NarInfoDiskCache::oValid:
             debug("Returning a cached realisation for %s", id.to_string());
-                callback(maybeCachedRealisation);
+            return maybeCachedRealisation;
-                return;
         case NarInfoDiskCache::oInvalid:
             debug(
                 "Returning a cached missing realisation for %s",
                 id.to_string());
-                callback(nullptr);
+            return nullptr;
-                return;
         case NarInfoDiskCache::oUnknown:
             break;
         }
     }
-    } catch (...) {
-        return callback.rethrow();
-    }
 
-    try {
     auto info = queryRealisationUncached(id);
 
     if (diskCache) {
@@ -753,28 +745,7 @@ void Store::queryRealisation(const DrvOutput & id,
             diskCache->upsertAbsentRealisation(getUri(), id);
     }
 
-        callback(std::shared_ptr<const Realisation>(info));
+    return info;
-
-    } catch (...) {
-        callback.rethrow();
-    }
-}
-
-std::shared_ptr<const Realisation> Store::queryRealisation(const DrvOutput & id)
-{
-    using RealPtr = std::shared_ptr<const Realisation>;
-    std::promise<RealPtr> promise;
-
-    queryRealisation(id,
-        {[&](std::future<RealPtr> result) {
-            try {
-                promise.set_value(result.get());
-            } catch (...) {
-                promise.set_exception(std::current_exception());
-            }
-        }});
-
-    return promise.get_future().get();
 }
 
 void Store::substitutePaths(const StorePathSet & paths)

src/libstore/store-api.hh

@@ -371,12 +371,6 @@ public:
      */
     std::shared_ptr<const Realisation> queryRealisation(const DrvOutput &);
 
-    /**
-     * Asynchronous version of queryRealisation().
-     */
-    void queryRealisation(const DrvOutput &,
-        Callback<std::shared_ptr<const Realisation>> callback) noexcept;
-
 
     /**
      * Check whether the given valid path info is sufficiently attested, by