libstore: asyncify createGeneration

Change-Id: Iae47a0f732b2f0fe54525917c091169f4be2214e

lix/legacy/nix-env.cc

@@ -795,10 +795,10 @@ static void opSet(Globals & globals, Strings opFlags, Strings opArgs)
     );
 
     debug("switching to new user environment");
-    Path generation = createGeneration(
+    Path generation = globals.aio.blockOn(createGeneration(
         *store2,
         globals.profile,
-        drv.queryOutPath(*state));
+        drv.queryOutPath(*state)));
     switchLink(globals.profile, generation);
 }
 

lix/legacy/user-env.cc

@@ -142,7 +142,7 @@ bool createUserEnv(EvalState & state, DrvInfos & elems,
         }
 
         debug("switching to new user environment");
-        Path generation = createGeneration(*store2, profile, topLevelOut);
+        Path generation = state.aio.blockOn(createGeneration(*store2, profile, topLevelOut));
         switchLink(profile, generation);
     }
 

lix/libcmd/command.cc

@@ -231,7 +231,7 @@ void MixProfile::updateProfile(const StorePath & storePath)
     if (!store) throw Error("'--profile' is not supported for this Nix store");
     auto profile2 = absPath(*profile);
     switchLink(profile2,
-        createGeneration(*store, profile2, storePath));
+        aio().blockOn(createGeneration(*store, profile2, storePath)));
 }
 
 void MixProfile::updateProfile(const BuiltPaths & buildables)

lix/libstore/profiles.cc

@@ -70,8 +70,8 @@ static Path makeName(const Path & profile, GenerationNumber num)
 }
 
 
-Path createGeneration(LocalFSStore & store, Path profile, StorePath outPath)
-{
+kj::Promise<Result<Path>> createGeneration(LocalFSStore & store, Path profile, StorePath outPath)
+try {
     /* The new generation number should be higher than old the
        previous ones. */
     auto [gens, dummy] = findGenerations(profile);
@@ -87,7 +87,7 @@ Path createGeneration(LocalFSStore & store, Path profile, StorePath outPath)
                This helps keeping gratuitous installs/rebuilds from piling
                up uncontrolled numbers of generations, cluttering up the
                UI like grub. */
-            return last.path;
+            co_return last.path;
         }
 
         num = last.number;
@@ -104,7 +104,9 @@ Path createGeneration(LocalFSStore & store, Path profile, StorePath outPath)
     Path generation = makeName(profile, num + 1);
     store.addPermRoot(outPath, generation);
 
-    return generation;
+    co_return generation;
+} catch (...) {
+    co_return result::current_exception();
 }
 
 

lix/libstore/profiles.hh

@@ -96,7 +96,7 @@ class LocalFSStore;
  * The behavior of reusing existing generations like this makes this
  * procedure idempotent. It also avoids clutter.
  */
-Path createGeneration(LocalFSStore & store, Path profile, StorePath outPath);
+kj::Promise<Result<Path>> createGeneration(LocalFSStore & store, Path profile, StorePath outPath);
 
 /**
  * Unconditionally delete a generation

lix/nix/upgrade-nix.cc

@@ -257,7 +257,8 @@ struct CmdUpgradeNix : MixDryRun, EvalCommand
         // Build the new profile, and switch to it.
         StorePath const newProfile = manifest.build(store);
         printTalkative("built new profile '%s'", store->printStorePath(newProfile));
-        auto const newGeneration = createGeneration(*fsStore, this->profileDir, newProfile);
+        auto const newGeneration =
+            aio().blockOn(createGeneration(*fsStore, this->profileDir, newProfile));
         printTalkative(
             "switching '%s' to newly created generation '%s'",
             this->profileDir,