Code coverage for Python using Bazel 6.0.0

Question

I want to generate a code coverage report using Bazel for a Python project (my environment: macOS Ventura, M1 arm64, Python 3.10, Bazel 6.0).

The documentation states that for this task Bazel 6.0 and a modified version of coverage.py should work.

It suggests to create a requiremnts.txt with the following content:

git+https://github.com/ulfjack/coveragepy.git@lcov-support

extend the WORKSPACE file this way:

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

http_archive(
    name = "rules_python",
    url = "https://github.com/bazelbuild/rules_python/releases/download/0.5.0/rules_python-0.5.0.tar.gz",
    sha256 = "cd6730ed53a002c56ce4e2f396ba3b3be262fd7cb68339f0377a45e8227fe332",
)

load("@rules_python//python:pip.bzl", "pip_install")

pip_install(
   name = "python_deps",
   requirements = "//:requirements.txt",
)

And modify py_tests this way:

load("@python_deps//:requirements.bzl", "entry_point")

alias(
    name = "python_coverage_tools",
    actual = entry_point("coverage"),
)

py_test(
    name = "test",
    srcs = ["test.py"],
    env = {
        "PYTHON_COVERAGE": "$(location :python_coverage_tools)",
    },
    deps = [
        ":main",
        ":python_coverage_tools",
    ],
)

I followed this approach but get this error message:

ERROR: An error occurred during the fetch of repository 'python_deps':
   Traceback (most recent call last):
        File "/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/external/rules_python/python/pip_install/pip_repository.bzl", line 345, column 13, in _pip_repository_impl
                fail("rules_python failed: %s (%s)" % (result.stdout, result.stderr))
Error in fail: rules_python failed:  (Traceback (most recent call last):
  File "/opt/homebrew/Cellar/[email protected]/3.10.9/Frameworks/Python.framework/Versions/3.10/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/opt/homebrew/Cellar/[email protected]/3.10.9/Frameworks/Python.framework/Versions/3.10/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/external/rules_python/python/pip_install/extract_wheels/parse_requirements_to_bzl.py", line 322, in <module>
    main(requirement_file)
  File "/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/external/rules_python/python/pip_install/extract_wheels/parse_requirements_to_bzl.py", line 309, in main
    generate_parsed_requirements_contents(
  File "/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/external/rules_python/python/pip_install/extract_wheels/parse_requirements_to_bzl.py", line 114, in generate_parsed_requirements_contents
    repo_names_and_reqs = repo_names_and_requirements(
  File "/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/external/rules_python/python/pip_install/extract_wheels/parse_requirements_to_bzl.py", line 69, in repo_names_and_requirements
    return [
  File "/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/external/rules_python/python/pip_install/extract_wheels/parse_requirements_to_bzl.py", line 71, in <listcomp>
    bazel.sanitise_name(ir.name, prefix=repo_prefix),
  File "/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/external/rules_python/python/pip_install/extract_wheels/bazel.py", line 25, in sanitise_name
    return prefix + name.replace("-", "_").replace(".", "_").lower()
AttributeError: 'NoneType' object has no attribute 'replace'

Any ideas how to get proper code coverage for a Bazel based Python project are welcome.

I tried also to run the code coverage command this way:

bazel coverage --test_env=PYTHON_COVERAGE=/Users/vertexahn/dev/coveragepy/__main__.py //tests:test_main

This results in:

exec ${PAGER:-/usr/bin/less} "$0" || exit 1
Executing tests from //tests:test_main
-----------------------------------------------------------------------------
Unrecognized option '[run] relative_files=' in config file /private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/sandbox/darwin-sandbox/79/execroot/__main__/bazel-out/darwin_arm64-fastbuild/testlogs/_coverage/tests/test_main/test/.coveragerc
Unknown command: 'lcov'
Use 'coverage help' for help.
--
Coverage runner: Not collecting coverage for failed test.
The following commands failed with status 1
/private/var/tmp/_bazel_vertexwahn/401174f4ee3f8d1aff86fa2a0c8c5dbe/sandbox/darwin-sandbox/79/execroot/__main__/bazel-out/darwin_arm64-fastbuild/bin/tests/test_main.runfiles/__main__/tests/test_main

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