libstore: asyncify ParsedDerivation::prepareStructuredAttrs

Change-Id: I6c34bb5fc67046a0c25486bf4f2fa5bbaa62eacf

lix/legacy/nix-build.cc

@@ -470,7 +470,7 @@ static void main_nix_build(AsyncIoRoot & aio, std::string programName, Strings a
 
             ParsedDerivation parsedDrv(drvInfo.requireDrvPath(*state), drv);
 
-            if (auto structAttrs = parsedDrv.prepareStructuredAttrs(*store, inputs)) {
+            if (auto structAttrs = aio.blockOn(parsedDrv.prepareStructuredAttrs(*store, inputs))) {
                 auto json = structAttrs.value();
                 structuredAttrsRC = writeStructuredAttrsShell(json);
 

lix/libstore/build/local-derivation-goal.cc

@@ -916,7 +916,9 @@ void LocalDerivationGoal::initEnv()
 
 kj::Promise<Result<void>> LocalDerivationGoal::writeStructuredAttrs()
 try {
-    if (auto structAttrsJson = parsedDrv->prepareStructuredAttrs(worker.store, inputPaths)) {
+    if (auto structAttrsJson =
+            TRY_AWAIT(parsedDrv->prepareStructuredAttrs(worker.store, inputPaths)))
+    {
         auto json = structAttrsJson.value();
         nlohmann::json rewritten;
         for (auto & [i, v] : json["outputs"].get<nlohmann::json::object_t>()) {

lix/libstore/parsed-derivations.cc

@@ -134,10 +134,11 @@ bool ParsedDerivation::useUidRange() const
 
 static std::regex shVarName("[A-Za-z_][A-Za-z0-9_]*");
 
-std::optional<nlohmann::json> ParsedDerivation::prepareStructuredAttrs(Store & store, const StorePathSet & inputPaths)
-{
+kj::Promise<Result<std::optional<nlohmann::json>>>
+ParsedDerivation::prepareStructuredAttrs(Store & store, const StorePathSet & inputPaths)
+try {
     auto structuredAttrs = getStructuredAttrs();
-    if (!structuredAttrs) return std::nullopt;
+    if (!structuredAttrs) co_return std::nullopt;
 
     auto json = *structuredAttrs;
 
@@ -155,12 +156,14 @@ std::optional<nlohmann::json> ParsedDerivation::prepareStructuredAttrs(Store & s
             for (auto & p : *i)
                 storePaths.insert(store.toStorePath(p.get<std::string>()).first);
             json[i.key()] = store.pathInfoToJSON(
-                RUN_ASYNC_IN_NEW_THREAD(store.exportReferences(storePaths, inputPaths)), false, true
+                TRY_AWAIT(store.exportReferences(storePaths, inputPaths)), false, true
             );
         }
     }
 
-    return json;
+    co_return json;
+} catch (...) {
+    co_return result::current_exception();
 }
 
 /* As a convenience to bash scripts, write a shell file that

lix/libstore/parsed-derivations.hh

@@ -41,7 +41,8 @@ public:
 
     bool useUidRange() const;
 
-    std::optional<nlohmann::json> prepareStructuredAttrs(Store & store, const StorePathSet & inputPaths);
+    kj::Promise<Result<std::optional<nlohmann::json>>>
+    prepareStructuredAttrs(Store & store, const StorePathSet & inputPaths);
 };
 
 std::string writeStructuredAttrsShell(const nlohmann::json & json);