External repository referring unexported files

[linzhp]

Description of the problem / feature request:

When an external repository refers to an unexported files, builds can still succeed, only queries with deps would fail. This is inconsistent.

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

• Create a workspace like this:

-- WORKSPACE --
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "com_google_protobuf",
    sha256 = "d0f5f605d0d656007ce6c8b5a82df3037e1d8fe8b121ed42e536f569dec16113",
    strip_prefix = "protobuf-3.14.0",
    urls = [
        "https://mirror.bazel.build/github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
        "https://github.com/protocolbuffers/protobuf/archive/v3.14.0.tar.gz",
    ],
)

load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")

protobuf_deps()
-- BUILD.bazel --

• Run bazel build @zlib//:all, it would succeed
• Run bazel query 'deps(//external:zlib)', it would fail with:

ERROR: /private/tmp/protobuf/WORKSPACE:15:14: no such target '@com_google_protobuf//:third_party/zlib.BUILD': Label '@com_google_protobuf//:third_party/zlib.BUILD' crosses boundary of subpackage '@com_google_protobuf//third_party' and referenced by '//external:zlib'
ERROR: /private/tmp/protobuf/WORKSPACE:15:14: no such target '@com_google_protobuf//:third_party/zlib.BUILD': target 'third_party/zlib.BUILD' not declared in package ''; however, a source file of this name exists.  (Perhaps add 'exports_files(["third_party/zlib.BUILD"])' to /BUILD?) defined by /private/var/tmp/_bazel_zplin/67edb565efa10fe0537e4ddaba8aef74/external/com_google_protobuf/BUILD and referenced by '//external:zlib'
ERROR: Evaluation of query "deps(//external:zlib)" failed: errors were encountered while computing transitive closure

What operating system are you running Bazel on?

macOS

What's the output of bazel info release?

release 5.1.0

Any other information, logs, or outputs that you want to share?

This bug has existed for a long time. #8175 is a symptom of it. #15134 fixed the symptom, but it doesn't prevent it from coming back.

[meteorcloudy]

I think the reason is that protobuf should use @com_google_protobuf//third_party:zlib.BUILD at here

But somehow we didn't check if the label is valid when using in the WORKSPACE file.

[meteorcloudy]

I think the underlying problem is that when a label is used in the WORKSPACE file to reference a file, we are actually not loading the target (that's when we check if the label is crossing boundary). But we do try to load targets from the label when running bazel query.

[github-actions]

Thank you for contributing to the Bazel repository! This issue has been marked as stale since it has not had any activity in the last 1+ years. It will be closed in the next 14 days unless any other activity occurs or one of the following labels is added: "not stale", "awaiting-bazeler". Please reach out to the triage team (@bazelbuild/triage) if you think this issue is still relevant or you are interested in getting the issue resolved.

[linzhp]

@bazelbuild/triage Can you keep this open?

[Wyverald]

bazel query deps(//external:foo) was never going to work as targets under //external are pseudo-targets and don't actually behave like other, actual build targets. Regardless, we won't be fixing this as the entire //external package will be going away with WORKSAPCE deprecation.