Empty input directories are omitted

[Monnoroch]

Rules proto grpc project runs cp -r on multiple input directories. Each directory is created by an aspect for a proto_library target. During local execution Bazel creates output directories defined by declare_directory() for aspects and then calls the action to populate them. If the action doesn't produce any files empty directories stay as they were. When the same build is executed remotely with Buildbarn empty directories are not present in the inputs (while non-empty ones are there). I assume this is a bug in Buildbarn -- it doesn't download empty directory trees. #47 makes me think that if there's no files the directory tree will not be built. Since declare_directory() was called I would expect it to be present in dependent actions no matter it's contents.

[Monnoroch]

Any comments on this issue? Is it considered a bug of the buildbarn implementation or should I file a PR to the proto rules repo?

[EdSchouten]

Can you check whether this still holds with the latest copy of Buildbarn? It may be that this was related to #46. Be sure to also explore the input root in bb-browser. If there is no directory there, then there is little we can do; Bazel doesn’t provide it to us then.

[Monnoroch]

Nope, still the same problem.

[EdSchouten]

Have you inspected bb-browser to see what the input root looks like? If the input root doesn't show these directories, then there is no way you can expect Buildbarn to create them for you.

[Monnoroch]

Yes, it doesn't have the empty directories. Only directories with files in them.

[EdSchouten]

Then in that case Buildbarn is working as expected. It instantiates the file system as provided by Bazel. Be sure to file a new issue against Bazel itself to report this issue!