proto_library: warning: directory does not exist

[jayconrod]

Description of the problem / feature request:

Building proto_library targets for Well Known Types in @com_google_protobuf emits warnings like the one below. The build succeeds, but it would be nice if the warning can be fixed or removed.

$ bazel build @com_google_protobuf//:any_proto
...
INFO: From Generating Descriptor Set proto_library @com_google_protobuf//:any_proto:
external/com_google_protobuf: warning: directory does not exist.
...

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

# WORKSPACE
load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")

git_repository(
    name = "com_google_protobuf",
    remote = "https://github.com/protocolbuffers/protobuf",
    tag = "v3.6.1.3",
)

git_repository(
    name = "bazel_skylib",
    remote = "https://github.com/bazelbuild/bazel-skylib",
    tag = "0.6.0",
)

bazel build @com_google_protobuf//:any_proto

What operating system are you running Bazel on?

Linux amd64

What's the output of bazel info release?

release 0.21.0

This does not happen in 0.20.0, but it does happen in 0.22.0rc2.

[jayconrod]

@lberki I wonder if this is related to recent source root changes?

[lberki]

/cc @haberman

Probably, I suppose? We did reshuffle the way protoc is called a bit. I'm traveling this week and next, though, so I probably won't be able to look at it closely until I get back home.

@dbabkin , can you help out?

[thaidn]

Friendly ping. This still happens in 0.22.0.

[dbabkin]

Hi,
There is no ETA when that will be fixed.
Priority of this task is low, as it is warning only.

[steeve]

Small ping, still happening in 0.25.3

[dapirian]

Ping again, this is extremely annoying and spammy.

[lberki]

Update: I have a change under review that will fix this issue. Let's see how the review goes. It's not complicated, so it shouldn't be problematic.