libstore: asyncify Store::substitutePaths

Change-Id: I8cb6822ad9145fbcf0f98f32c121482c3a3db2a8

lix/legacy/nix-store.cc

@@ -881,7 +881,7 @@ static void opServe(AsyncIoRoot & aio, Strings opFlags, Strings opArgs)
                         store->addTempRoot(path);
 
                 if (substitute && writeAllowed) {
-                    store->substitutePaths(paths);
+                    aio.blockOn(store->substitutePaths(paths));
                 }
 
                 auto valid = store->queryValidPaths(paths);

lix/libstore/daemon.cc

@@ -289,7 +289,7 @@ static void performOp(AsyncIoRoot & aio, TunnelLogger * logger, ref<Store> store
 
         logger->startWork();
         if (substitute) {
-            store->substitutePaths(paths);
+            aio.blockOn(store->substitutePaths(paths));
         }
         auto res = store->queryValidPaths(paths, substitute);
         logger->stopWork();

lix/libstore/store-api.cc

@@ -4,6 +4,7 @@
 #include "lix/libstore/store-api.hh"
 #include "lix/libstore/nar-info-disk-cache.hh"
 #include "lix/libutil/async.hh"
+#include "lix/libutil/result.hh"
 #include "lix/libutil/thread-pool.hh"
 #include "lix/libutil/url.hh"
 #include "lix/libutil/archive.hh"
@@ -801,8 +802,8 @@ std::shared_ptr<const Realisation> Store::queryRealisation(const DrvOutput & id)
     return info;
 }
 
-void Store::substitutePaths(const StorePathSet & paths)
-{
+kj::Promise<Result<void>> Store::substitutePaths(const StorePathSet & paths)
+try {
     std::vector<DerivedPath> paths2;
     for (auto & path : paths)
         if (!path.isDerivation())
@@ -816,10 +817,14 @@ void Store::substitutePaths(const StorePathSet & paths)
         try {
             std::vector<DerivedPath> subs;
             for (auto & p : willSubstitute) subs.emplace_back(DerivedPath::Opaque{p});
-            RUN_ASYNC_IN_NEW_THREAD(buildPaths(subs));
+            TRY_AWAIT(buildPaths(subs));
         } catch (Error & e) {
             logWarning(e.info());
         }
+
+    co_return result::success();
+} catch (...) {
+    co_return result::current_exception();
 }
 
 

lix/libstore/store-api.hh

@@ -354,7 +354,7 @@ public:
      * implements nix-copy-closure's --use-substitutes
      * flag.
      */
-    void substitutePaths(const StorePathSet & paths);
+    kj::Promise<Result<void>> substitutePaths(const StorePathSet & paths);
 
     /**
      * Query which of the given paths is valid. Optionally, try to