Error when running bazel as part of a pixi project

[traversaro]

I am trying to compile a basic bazel project using a bazel installed with pixi, and I got errors like:

traversaro@IITBMP014LW012:~/how-to-export-cpp-library$ pixi run build-bazel
✨ Pixi task (build-bazel in bazel): bazel build -s //...
WARNING: Target pattern parsing failed.
ERROR: Skipping '//...': error loading package under directory '': error loading package '.pixi/envs/bazel/share/bazel/8f471b04384191fcb7519415de4cf9b4/external/rules_python~/tools/publish': Label '//python:pip.bzl' is invalid because 'python' is not a package; perhaps you meant to put the colon here: '//:python/pip.bzl'?
ERROR: error loading package under directory '': error loading package '.pixi/envs/bazel/share/bazel/8f471b04384191fcb7519415de4cf9b4/external/rules_python~/tools/publish': Label '//python:pip.bzl' is invalid because 'python' is not a package; perhaps you meant to put the colon here: '//:python/pip.bzl'?
INFO: Elapsed time: 0.198s
INFO: 0 processes.
ERROR: Build did NOT complete successfully

or

✨ Pixi task (build-bazel in bazel): bazel build -s //...
Starting local Bazel server and connecting to it...
WARNING: Target pattern parsing failed.
ERROR: Skipping '//...': error loading package under directory '': error loading package '.pixi/envs/bazel/share/bazel_toolchain': cannot load '//.pixi/envs/bazel/share/bazel_toolchain:cc_toolchain_build_config.bzl': no such file
ERROR: error loading package under directory '': error loading package '.pixi/envs/bazel/share/bazel_toolchain': cannot load '//.pixi/envs/bazel/share/bazel_toolchain:cc_toolchain_build_config.bzl': no such file
INFO: Elapsed time: 8.458s
INFO: 0 processes.
ERROR: Build did NOT complete successfully
FAILED:
    Fetching repository @@rules_cc~; starting

how can I fix this?

[traversaro]

The problem is that your bazel workspace correspond to your pixi workspace, where the .pixi folder (that contains the bazel installation) is found. To avoid that bazel get confused by this, just create a .bazelignore file at the root of your bazel workspace/pixi project, and add a line with the .pixi folder to it.

[zbowling]

Better than bazelignore, which doesn't support globs, add this to your REPO.bazel:

ignore_directories([
    "**/.pixi",
])

[zbowling]

Which version of bazel are you using?

It was added in 8.0 and then back ported I believe to the 7.0 versions. If you are on an older versions then it might throw that error and you are stuck with being explicit everywhere with .bazelignore.

See:

https://bazel.build/rules/lib/globals/repo#ignore_directories

Here is the bug where the feature was added: bazelbuild/bazel#7093

[traversaro]

Which version of bazel are you using?

It was added in 8.0 and then back ported I believe to the 7.0 versions. If you are on an older versions then it might throw that error and you are stuck with being explicit everywhere with .bazelignore.

See:

https://bazel.build/rules/lib/globals/repo#ignore_directories

Here is the bug where the feature was added: bazelbuild/bazel#7093

Bazel 7.5.0, that is the latest available in conda-forge (and hence what realistically pixi users would install in a pixi env).

[zbowling]

Oh wow. Let me check why bazel 8 hasn't shipped yet on conda-forge.

It looks like the maintainers have ignored updating the feedstock for 8.0 for 3 months.

[traversaro]

I guess there were packaging problem, the CI seems failing (and that does not surprise me, Bazel and Bazel-based projects are always tricky to handle).

[zbowling]

I spent some time trying to update bazel. It's a cluster the way it's built on conda-forge. I got a build going but breaks ppc64le.

[traversaro]

In case anyone reads this, bazel 8.3.1 introduced another problem related to use a bazel install in the .pixi folder that can't be worked around by adding the .pixi folder to .bazelignore, see bazelbuild/bazel#26384 and robotology/osqp-eigen#218 .