libfetchers: asyncify fetchToStore

Change-Id: I0153cefbe974137ab3d4fd9218c8a77137976f8c

lix/libcmd/installable-value.cc

@@ -47,7 +47,9 @@ std::optional<DerivedPathWithInfo> InstallableValue::trySinglePathToDerivedPaths
 )
 {
     if (v.type() == nPath) {
-        auto storePath = fetchToStore(*evaluator->store, state.ctx.paths.checkSourcePath(v.path()));
+        auto storePath = state.aio.blockOn(
+            fetchToStore(*evaluator->store, state.ctx.paths.checkSourcePath(v.path()))
+        );
         return {{
             .path = DerivedPath::Opaque {
                 .path = std::move(storePath),

lix/libexpr/eval.cc

@@ -2366,13 +2366,20 @@ try {
 
     auto dstPath = i != srcToStore.end()
         ? i->second
-        : [&]() {
-            auto dstPath = fetchToStore(*store, checkSourcePath(path), path.baseName(), FileIngestionMethod::Recursive, nullptr, repair);
+        : ({
+            auto dstPath = TRY_AWAIT(fetchToStore(
+                *store,
+                checkSourcePath(path),
+                path.baseName(),
+                FileIngestionMethod::Recursive,
+                nullptr,
+                repair
+            ));
             allowPath(dstPath);
             srcToStore.insert_or_assign(path, dstPath);
             printMsg(lvlChatty, "copied source '%1%' -> '%2%'", path, store->printStorePath(dstPath));
-            return dstPath;
-        }();
+            std::move(dstPath);
+        });
 
     context.insert(NixStringContextElem::Opaque {
         .path = dstPath

lix/libexpr/primops.cc

@@ -1557,14 +1557,14 @@ static void addPath(
             });
 
         if (!expectedHash || !state.ctx.store->isValidPath(*expectedStorePath)) {
-            auto dstPath = fetchToStore(
+            auto dstPath = state.aio.blockOn(fetchToStore(
                 *state.ctx.store,
                 state.ctx.paths.checkSourcePath(CanonPath(path)),
                 name,
                 method,
                 &filter,
                 state.ctx.repair
-            );
+            ));
             if (expectedHash && expectedStorePath != dstPath)
                 state.ctx.errors.make<EvalError>(
                     "store path mismatch in (possibly filtered) path added from '%s'",

lix/libfetchers/fetch-to-store.cc

@@ -4,22 +4,24 @@
 
 namespace nix {
 
-StorePath fetchToStore(
+kj::Promise<Result<StorePath>> fetchToStore(
     Store & store,
     const CheckedSourcePath & path,
     std::string_view name,
     FileIngestionMethod method,
     PathFilter * filter,
     RepairFlag repair)
-{
+try {
     Activity act(*logger, lvlChatty, actUnknown, fmt("copying '%s' to the store", path));
 
     auto filter2 = filter ? *filter : defaultPathFilter;
 
-    return
+    co_return
         settings.readOnlyMode
         ? store.computeStorePathForPath(name, path.canonical().abs(), method, HashType::SHA256, filter2).first
         : store.addToStore(name, path.canonical().abs(), method, HashType::SHA256, filter2, repair);
+} catch (...) {
+    co_return result::current_exception();
 }
 
 

lix/libfetchers/fetch-to-store.hh

@@ -11,7 +11,7 @@ namespace nix {
 /**
  * Copy the `path` to the Nix store.
  */
-StorePath fetchToStore(
+kj::Promise<Result<StorePath>> fetchToStore(
     Store & store,
     const CheckedSourcePath & path,
     std::string_view name = "source",