feat(3p/nix): Implement FindRoots, CollectGarbage

Implement the RPC client and server handlers for the FindRoots and
CollectGarbage RPC calls

Change-Id: Ifa5d582c6a33bd1e7661ac2fc860505ef404dad0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1656
Tested-by: BuildkiteCI
Reviewed-by: kanepyork <rikingcoding@gmail.com>

third_party/nix/src/libstore/rpc-store.cc

@@ -418,11 +418,36 @@ void RpcStore::syncWithGC() {
 }
 
 Roots RpcStore::findRoots(bool censor) {
-  throw Unsupported(absl::StrCat("Not implemented ", __func__));
+  ClientContext ctx;
+  proto::FindRootsResponse response;
+  SuccessOrThrow(stub_->FindRoots(&ctx, kEmpty, &response));
+  Roots result;
+
+  for (const auto& [target, links] : response.roots()) {
+    auto link_paths = FillFrom<std::unordered_set<std::string>>(links.paths());
+    result.insert({target, link_paths});
+  }
+
+  return result;
 }
 
 void RpcStore::collectGarbage(const GCOptions& options, GCResults& results) {
-  throw Unsupported(absl::StrCat("Not implemented ", __func__));
+  ClientContext ctx;
+  proto::CollectGarbageRequest request;
+  request.set_action(options.ActionToProto());
+  for (const auto& path : options.pathsToDelete) {
+    request.add_paths_to_delete(path);
+  }
+  request.set_ignore_liveness(options.ignoreLiveness);
+  request.set_max_freed(options.maxFreed);
+
+  proto::CollectGarbageResponse response;
+  SuccessOrThrow(stub_->CollectGarbage(&ctx, request, &response));
+
+  for (const auto& path : response.deleted_paths()) {
+    results.paths.insert(path);
+  }
+  results.bytesFreed = response.bytes_freed();
 }
 
 void RpcStore::optimiseStore() {

third_party/nix/src/libstore/store-api.cc

@@ -77,6 +77,35 @@ nix::proto::BuildStatus BuildResult::status_to_proto() {
   }
 }
 
+std::optional<GCOptions::GCAction> GCActionFromProto(
+    nix::proto::GCAction gc_action) {
+  switch (gc_action) {
+    case nix::proto::GCAction::ReturnLive:
+      return GCOptions::GCAction::gcReturnLive;
+    case nix::proto::GCAction::ReturnDead:
+      return GCOptions::GCAction::gcReturnDead;
+    case nix::proto::GCAction::DeleteDead:
+      return GCOptions::GCAction::gcDeleteDead;
+    case nix::proto::GCAction::DeleteSpecific:
+      return GCOptions::GCAction::gcDeleteSpecific;
+    default:
+      return {};
+  }
+}
+
+[[nodiscard]] const proto::GCAction GCOptions::ActionToProto() const {
+  switch (action) {
+    case GCOptions::GCAction::gcReturnLive:
+      return nix::proto::GCAction::ReturnLive;
+    case GCOptions::GCAction::gcReturnDead:
+      return nix::proto::GCAction::ReturnDead;
+    case GCOptions::GCAction::gcDeleteDead:
+      return nix::proto::GCAction::DeleteDead;
+    case GCOptions::GCAction::gcDeleteSpecific:
+      return nix::proto::GCAction::DeleteSpecific;
+  }
+}
+
 bool Store::isInStore(const Path& path) const {
   return isInDir(path, storeDir);
 }

third_party/nix/src/libstore/store-api.hh

@@ -80,8 +80,13 @@ struct GCOptions {
 
   /* Stop after at least `maxFreed' bytes have been freed. */
   unsigned long long maxFreed{std::numeric_limits<unsigned long long>::max()};
+
+  [[nodiscard]] const proto::GCAction ActionToProto() const;
 };
 
+std::optional<GCOptions::GCAction> GCActionFromProto(
+    nix::proto::GCAction gc_action);
+
 struct GCResults {
   /* Depending on the action, the GC roots, or the paths that would
      be or have been deleted. */