Give DerivationBuilder a LocalStore not Store

This is just more honest, since we downcasted it to `LocalStore` in many
places. We had the downcast before because it wasn't needed in the hook
case, just the local building case, but now that `DerivationBuilder` is
separated and just does the building case, we have formalized the
boundary where the single downcast should occur.

src/libstore/build/derivation-building-goal.cc

@@ -673,10 +673,13 @@ Goal::Co DerivationBuildingGoal::tryToBuild()
                 }
             };
 
+            auto * localStoreP = dynamic_cast<LocalStore *>(&worker.store);
+            assert(localStoreP);
+
             /* If we have to wait and retry (see below), then `builder` will
                already be created, so we don't need to create it again. */
             builder = makeDerivationBuilder(
-                worker.store,
+                *localStoreP,
                 std::make_unique<DerivationBuildingGoalCallbacks>(*this, builder),
                 DerivationBuilderParams{
                     drvPath,

src/libstore/unix/build/chroot-derivation-builder.cc

@@ -5,7 +5,7 @@ namespace nix {
 struct ChrootDerivationBuilder : virtual DerivationBuilderImpl
 {
     ChrootDerivationBuilder(
-        Store & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
+        LocalStore & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
         : DerivationBuilderImpl{store, std::move(miscMethods), std::move(params)}
     {
     }
@@ -178,7 +178,7 @@ struct ChrootDerivationBuilder : virtual DerivationBuilderImpl
                     continue;
                 if (buildMode != bmCheck && status.known->isValid())
                     continue;
-                auto p = store.toRealPath(status.known->path);
+                auto p = store.Store::toRealPath(status.known->path);
                 if (pathExists(chrootRootDir + p))
                     std::filesystem::rename((chrootRootDir + p), p);
             }

src/libstore/unix/build/darwin-derivation-builder.cc

@@ -21,7 +21,7 @@ struct DarwinDerivationBuilder : DerivationBuilderImpl
     bool useSandbox;
 
     DarwinDerivationBuilder(
-        Store & store,
+        LocalStore & store,
         std::unique_ptr<DerivationBuilderCallbacks> miscMethods,
         DerivationBuilderParams params,
         bool useSandbox)

src/libstore/unix/build/derivation-builder.cc

@@ -61,14 +61,14 @@ class DerivationBuilderImpl : public DerivationBuilder, public DerivationBuilder
 {
 protected:
 
-    Store & store;
+    LocalStore & store;
 
     std::unique_ptr<DerivationBuilderCallbacks> miscMethods;
 
 public:
 
     DerivationBuilderImpl(
-        Store & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
+        LocalStore & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
         : DerivationBuilderParams{std::move(params)}
         , store{store}
         , miscMethods{std::move(miscMethods)}
@@ -424,13 +424,6 @@ void handleDiffHook(
 
 const Path DerivationBuilderImpl::homeDir = "/homeless-shelter";
 
-static LocalStore & getLocalStore(Store & store)
-{
-    auto p = dynamic_cast<LocalStore *>(&store);
-    assert(p);
-    return *p;
-}
-
 void DerivationBuilderImpl::killSandbox(bool getStats)
 {
     if (buildUser) {
@@ -631,10 +624,9 @@ bool DerivationBuilderImpl::decideWhetherDiskFull()
        so, we don't mark this build as a permanent failure. */
 #if HAVE_STATVFS
     {
-        auto & localStore = getLocalStore(store);
         uint64_t required = 8ULL * 1024 * 1024; // FIXME: make configurable
         struct statvfs st;
-        if (statvfs(localStore.config->realStoreDir.get().c_str(), &st) == 0
+        if (statvfs(store.config->realStoreDir.get().c_str(), &st) == 0
             && (uint64_t) st.f_bavail * st.f_bsize < required)
             diskFull = true;
         if (statvfs(tmpDir.c_str(), &st) == 0 && (uint64_t) st.f_bavail * st.f_bsize < required)
@@ -712,7 +704,7 @@ void DerivationBuilderImpl::startBuilder()
                 Magenta(drv.platform),
                 concatStringsSep(", ", drvOptions.getRequiredSystemFeatures(drv)),
                 Magenta(settings.thisSystem),
-                concatStringsSep<StringSet>(", ", store.config.systemFeatures));
+                concatStringsSep<StringSet>(", ", store.Store::config.systemFeatures));
 
         // since aarch64-darwin has Rosetta 2, this user can actually run x86_64-darwin on their hardware - we should
         // tell them to run the command to install Darwin 2
@@ -724,7 +716,7 @@ void DerivationBuilderImpl::startBuilder()
         throw BuildError(msg);
     }
 
-    auto buildDir = getLocalStore(store).config->getBuildDir();
+    auto buildDir = store.config->getBuildDir();
 
     createDirs(buildDir);
 
@@ -1173,7 +1165,7 @@ void DerivationBuilderImpl::startDaemon()
 
     auto store = makeRestrictedStore(
         [&] {
-            auto config = make_ref<LocalStore::Config>(*getLocalStore(this->store).config);
+            auto config = make_ref<LocalStore::Config>(*this->store.config);
             config->pathInfoCacheSize = 0;
             config->stateDir = "/no-such-path";
             config->logDir = "/no-such-path";
@@ -1839,8 +1831,6 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
             }
         }
 
-        auto & localStore = getLocalStore(store);
-
         if (buildMode == bmCheck) {
 
             if (!store.isValidPath(newInfo.path))
@@ -1876,8 +1866,8 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
             /* Since we verified the build, it's now ultimately trusted. */
             if (!oldInfo.ultimate) {
                 oldInfo.ultimate = true;
-                localStore.signPathInfo(oldInfo);
+                store.signPathInfo(oldInfo);
-                localStore.registerValidPaths({{oldInfo.path, oldInfo}});
+                store.registerValidPaths({{oldInfo.path, oldInfo}});
             }
 
             continue;
@@ -1891,12 +1881,12 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
                 debug("unreferenced input: '%1%'", store.printStorePath(i));
         }
 
-        localStore.optimisePath(actualPath, NoRepair); // FIXME: combine with scanForReferences()
+        store.optimisePath(actualPath, NoRepair); // FIXME: combine with scanForReferences()
         miscMethods->markContentsGood(newInfo.path);
 
         newInfo.deriver = drvPath;
         newInfo.ultimate = true;
-        localStore.signPathInfo(newInfo);
+        store.signPathInfo(newInfo);
 
         finish(newInfo.path);
 
@@ -1904,7 +1894,7 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
            isn't statically known so that we can safely unlock the path before
            the next iteration */
         if (newInfo.ca)
-            localStore.registerValidPaths({{newInfo.path, newInfo}});
+            store.registerValidPaths({{newInfo.path, newInfo}});
 
         infos.emplace(outputName, std::move(newInfo));
     }
@@ -1925,13 +1915,11 @@ SingleDrvOutputs DerivationBuilderImpl::registerOutputs()
        paths referenced by each of them.  If there are cycles in the
        outputs, this will fail. */
     {
-        auto & localStore = getLocalStore(store);
-
         ValidPathInfos infos2;
         for (auto & [outputName, newInfo] : infos) {
             infos2.insert_or_assign(newInfo.path, newInfo);
         }
-        localStore.registerValidPaths(infos2);
+        store.registerValidPaths(infos2);
     }
 
     /* In case of a fixed-output derivation hash mismatch, throw an
@@ -2164,7 +2152,7 @@ StorePath DerivationBuilderImpl::makeFallbackPath(const StorePath & path)
 namespace nix {
 
 std::unique_ptr<DerivationBuilder> makeDerivationBuilder(
-    Store & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
+    LocalStore & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
 {
     bool useSandbox = false;
 
@@ -2191,8 +2179,7 @@ std::unique_ptr<DerivationBuilder> makeDerivationBuilder(
             useSandbox = params.drv.type().isSandboxed() && !params.drvOptions.noChroot;
     }
 
-    auto & localStore = getLocalStore(store);
+    if (store.storeDir != store.config->realStoreDir.get()) {
-    if (localStore.storeDir != localStore.config->realStoreDir.get()) {
 #ifdef __linux__
         useSandbox = true;
 #else

src/libstore/unix/build/linux-derivation-builder.cc

@@ -191,7 +191,7 @@ struct ChrootLinuxDerivationBuilder : ChrootDerivationBuilder, LinuxDerivationBu
     std::optional<Path> cgroup;
 
     ChrootLinuxDerivationBuilder(
-        Store & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
+        LocalStore & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params)
         : DerivationBuilderImpl{store, std::move(miscMethods), std::move(params)}
         , ChrootDerivationBuilder{store, std::move(miscMethods), std::move(params)}
         , LinuxDerivationBuilder{store, std::move(miscMethods), std::move(params)}
@@ -492,7 +492,7 @@ struct ChrootLinuxDerivationBuilder : ChrootDerivationBuilder, LinuxDerivationBu
             createDirs(chrootRootDir + "/dev/shm");
             createDirs(chrootRootDir + "/dev/pts");
             ss.push_back("/dev/full");
-            if (store.config.systemFeatures.get().count("kvm") && pathExists("/dev/kvm"))
+            if (store.Store::config.systemFeatures.get().count("kvm") && pathExists("/dev/kvm"))
                 ss.push_back("/dev/kvm");
             ss.push_back("/dev/null");
             ss.push_back("/dev/random");

src/libstore/unix/include/nix/store/build/derivation-builder.hh

@@ -179,6 +179,6 @@ struct DerivationBuilder : RestrictionContext
 };
 
 std::unique_ptr<DerivationBuilder> makeDerivationBuilder(
-    Store & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params);
+    LocalStore & store, std::unique_ptr<DerivationBuilderCallbacks> miscMethods, DerivationBuilderParams params);
 
 } // namespace nix