libstore: asyncify Store::querySubstitutablePaths

the LocalStore implementation calls `getDefaultSubstituters`, which
calls `openStore`, which calls `Store::init`, which does network io
in binary caches, which will eventually be properly asyncified curl

Change-Id: If6a7a0294e2c4ba8e35722583be6ccde21ed6585

lix/legacy/nix-env.cc

@@ -231,7 +231,7 @@ static bool isPrebuilt(EvalState & state, DrvInfo & elem)
 {
     auto path = elem.queryOutPath(state);
     if (state.ctx.store->isValidPath(path)) return true;
-    return state.ctx.store->querySubstitutablePaths({path}).count(path);
+    return state.aio.blockOn(state.ctx.store->querySubstitutablePaths({path})).count(path);
 }
 
 
@@ -1103,7 +1103,7 @@ static void opQuery(Globals & globals, Strings opFlags, Strings opArgs)
                 i.setFailed();
             }
         validPaths = store.queryValidPaths(paths);
-        substitutablePaths = store.querySubstitutablePaths(paths);
+        substitutablePaths = globals.aio.blockOn(store.querySubstitutablePaths(paths));
     }
 
 

lix/libstore/daemon.cc

@@ -300,7 +300,7 @@ static void performOp(AsyncIoRoot & aio, TunnelLogger * logger, ref<Store> store
     case WorkerProto::Op::QuerySubstitutablePaths: {
         auto paths = WorkerProto::Serialise<StorePathSet>::read(*store, rconn);
         logger->startWork();
-        auto res = store->querySubstitutablePaths(paths);
+        auto res = aio.blockOn(store->querySubstitutablePaths(paths));
         logger->stopWork();
         to << WorkerProto::write(*store, wconn, res);
         break;

lix/libstore/local-store.cc

@@ -1062,9 +1062,9 @@ std::optional<StorePath> LocalStore::queryPathFromHashPart(const std::string & h
 }
 
 
-StorePathSet LocalStore::querySubstitutablePaths(const StorePathSet & paths)
-{
-    if (!settings.useSubstitutes) return StorePathSet();
+kj::Promise<Result<StorePathSet>> LocalStore::querySubstitutablePaths(const StorePathSet & paths)
+try {
+    if (!settings.useSubstitutes) co_return StorePathSet();
 
     StorePathSet remaining;
     for (auto & i : paths)
@@ -1089,7 +1089,9 @@ StorePathSet LocalStore::querySubstitutablePaths(const StorePathSet & paths)
         std::swap(remaining, remaining2);
     }
 
-    return res;
+    co_return res;
+} catch (...) {
+    co_return result::current_exception();
 }
 
 

lix/libstore/local-store.hh

@@ -199,7 +199,7 @@ public:
 
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override;
 
-    StorePathSet querySubstitutablePaths(const StorePathSet & paths) override;
+    kj::Promise<Result<StorePathSet>> querySubstitutablePaths(const StorePathSet & paths) override;
 
     bool pathInfoIsUntrusted(const ValidPathInfo &) override;
     bool realisationIsUntrusted(const Realisation & ) override;

lix/libstore/remote-store.cc

@@ -227,13 +227,15 @@ StorePathSet RemoteStore::queryAllValidPaths()
 }
 
 
-StorePathSet RemoteStore::querySubstitutablePaths(const StorePathSet & paths)
-{
+kj::Promise<Result<StorePathSet>> RemoteStore::querySubstitutablePaths(const StorePathSet & paths)
+try {
     auto conn(getConnection());
     conn->to << WorkerProto::Op::QuerySubstitutablePaths;
     conn->to << WorkerProto::write(*this, *conn, paths);
     conn.processStderr();
-    return WorkerProto::Serialise<StorePathSet>::read(*this, *conn);
+    return {WorkerProto::Serialise<StorePathSet>::read(*this, *conn)};
+} catch (...) {
+    return {result::current_exception()};
 }
 
 

lix/libstore/remote-store.hh

@@ -66,7 +66,7 @@ public:
     std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(const StorePath & path, Store * evalStore = nullptr) override;
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override;
 
-    StorePathSet querySubstitutablePaths(const StorePathSet & paths) override;
+    kj::Promise<Result<StorePathSet>> querySubstitutablePaths(const StorePathSet & paths) override;
 
     void querySubstitutablePathInfos(const StorePathCAMap & paths,
         SubstitutablePathInfos & infos) override;

lix/libstore/store-api.hh

@@ -477,7 +477,10 @@ public:
     /**
      * Query which of the given paths have substitutes.
      */
-    virtual StorePathSet querySubstitutablePaths(const StorePathSet & paths) { return {}; };
+    virtual kj::Promise<Result<StorePathSet>> querySubstitutablePaths(const StorePathSet & paths)
+    {
+        return {StorePathSet{}};
+    }
 
     /**
      * Query substitute info (i.e. references, derivers and download