Misleading error message on rule producing TreeArtifact with dangling links

[peakschris]

Description of the bug:

When a rule writes into a declare_directory and the written files including dangling symlinks, the following error is produced:

ERROR: /.../repo/BUILD.bazel:182:15: TreeArtifact src/container_images/repo/python4 was not created ERROR: /.../repo/BUILD.bazel:182:15: Extracting from external/python_tar_gz/file/downloaded to bazel-out/k8-opt/bin/.../repo/python4... failed: not all outputs were created or valid

This is misleading (it stumped me for 24 hours) because there clearly is content in that output folder.

The rule might be run by an extract task that is extracting a tar file into a directory - so the content might not be immediately familiar to the build engineer - it would be much more helpful if it said "dangling symlink found, invalid TreeArtifact content rejected" or somesuch.

Which category does this issue belong to?

Rules API

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

Extract a tar file containing a dangling symlink with aspect rules_binary

Which operating system are you running Bazel on?

ubuntu

What is the output of bazel info release?

release 7.1.1

If bazel info release returns development version or (@non-git), tell us how you built Bazel.

No response

What's the output of git remote get-url origin; git rev-parse HEAD ?

No response

Is this a regression? If yes, please try to identify the Bazel commit where the bug was introduced.

No response

Have you found anything relevant by searching the web?

No

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

bazel build //src/.../repo:extract_python -s

INFO: Invocation ID: e63770c3-016e-4597-9fca-16b9bc0f3fb2
INFO: Analyzed target //src/.../repo:extract_python (1 packages loaded, 3 targets configured).
SUBCOMMAND: # //src/.../repo:extract_python [action 'Extracting from external/python_tar_gz/file/downloaded to bazel-out/k8-opt/bin/src/.../repo/python4...', configuration: 61c861bbaa36efb2afa2cc798451e8fe0f84c14c81358840106b67dc10be5ba2, execution platform: @@tc_toolchain//platforms:x64_linux, mnemonic: TARExtract]
(cd /root/.cache/bazel/_bazel_root/188506c7b02e36f1e557ada8df8c1e08/execroot/_main &&
exec env -
BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
JAVA_HOME=../bazel_tools/jdk
bazel-out/k8-opt-exec-ST-92d7732a2b63/bin/src/.../repo/tar --same-permissions -zxf external/python_tar_gz/file/downloaded -C bazel-out/k8-opt/bin/src/.../repo/python4 bin)

Configuration: 61c861bbaa36efb2afa2cc798451e8fe0f84c14c81358840106b67dc10be5ba2

Execution platform: @@tc_toolchain//platforms:x64_linux

ERROR: /.../repo/BUILD.bazel:182:15: TreeArtifact src/container_images/repo/python4 was not created
ERROR: /apps/browchri/tc2406/src/container_images/repo/BUILD.bazel:182:15: Extracting from external/python_tar_gz/file/downloaded to bazel-out/k8-opt/bin/src/.../repo/python4... failed: not all outputs were created or valid
Target //src/.../repo:extract_python failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 1.591s, Critical Path: 1.45s
INFO: 2 processes: 1 internal, 1 processwrapper-sandbox.
ERROR: Build did NOT complete successfully

ls -l bazel-out/k8-opt/bin/src/.../repo/python4

total 4
dr-xr-xr-x 2 root root 4096 Apr 21 21:15 bin

ls -l bazel-out/k8-opt/bin/src/.../repo/python4/bin

total 22916
lrwxrwxrwx 1 root root 9 Apr 20 20:38 2to3 -> 2to3-3.10
lrwxrwxrwx 1 root root 8 Apr 20 20:38 idle3 -> idle3.10
lrwxrwxrwx 1 root root 9 Apr 20 20:38 pydoc3 -> pydoc3.10
lrwxrwxrwx 1 root root 10 Apr 20 20:38 python3 -> python3.10
lrwxrwxrwx 1 root root 17 Apr 20 20:38 python3-config -> python3.10-config
-r-xr-xr-x 1 root root 23458520 Apr 20 20:38 python3.10
-r-xr-xr-x 1 root root 3085 Apr 20 20:38 python3.10-config
`

[tjgq]

I think this has been fixed by b78d73f, which was cherry-picked into 7.1.2 (#21889) and 7.2.0 (#21889). Can you upgrade to 7.1.2 and confirm?

[peakschris]

Wonderful! Yes, 7.1.2 latest produces a much better error message:

/.../repo/BUILD.bazel:182:15: error while validating output tree artifact src/.../repo/python: child bin/2to3 is a dangling symbolic link

Thank you!