__init__.py still created, despite --incompatible_default_to_explicit_init_py

[staalb]

Description of the problem / feature request:

When --incompatible_default_to_explicit_init_py is passed, no __init__.py files are created for a py_binary target. However, when that target is used in a genrule, still the __init__.py files are created.

Feature requests: what underlying problem are you trying to solve with this feature?

I have a code generator written in Python, which depends on third party code which uses python namespace packages.

Invoking the py_binary target of the code generator works fine (provided that --incompatible_default_to_explicit_init_py is passed to Bazel). Using this target as a tool in a genrule or with ctx.actions.run fails because Bazel still creates __init__.py files in that case.

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

Consider the following BUILD file:

py_library(
    name = "lib1",
    srcs = glob(["pylib1/**/*.py"]),
    imports = ["pylib1"],
)

py_library(
    name = "lib2",
    srcs = glob(["pylib2/**/*.py"]),
    imports = ["pylib2"],
)

py_binary(
    name = "test",
    srcs = ["test.py"],
    deps = [":lib1", ":lib2"],
)

genrule(
    name = "gen",
    outs = ["out.txt"],
    cmd = "$(location :test)",
    tools = [":test"],
)

And test.py:

import foo.bar.a
import foo.bar.b

Furthermore, the following empty files exist:

• WORKSPACE
• pylib1/foo/bar/a.py
• pylib2/foo/bar/b.py

This command works as expected:
bazel run --incompatible_default_to_explicit_init_py :test

While this command unexpectedly fails:
bazel build --incompatible_default_to_explicit_init_py :gen

... with this error:

Traceback (most recent call last):
  File "/home/bart/.cache/bazel/_bazel_bart/6a2c2a526fcecf9ab777dfd64f329e17/sandbox/linux-sandbox/6/execroot/__main__/bazel-out/host/bin/test.runfiles/__main__/test.py", line 2, in <module>
    import foo.bar.b
ModuleNotFoundError: No module named 'foo.bar.b'

Probably caused because Bazel created __init__.py files:

$ find bazel-out/ -name __init__.py
bazel-out/host/bin/test.runfiles/__main__/pylib2/foo/__init__.py
bazel-out/host/bin/test.runfiles/__main__/pylib2/foo/bar/__init__.py
bazel-out/host/bin/test.runfiles/__main__/pylib2/__init__.py
bazel-out/host/bin/test.runfiles/__main__/pylib1/foo/__init__.py
bazel-out/host/bin/test.runfiles/__main__/pylib1/foo/bar/__init__.py
bazel-out/host/bin/test.runfiles/__main__/pylib1/__init__.py

Replace this line with your answer.

What operating system are you running Bazel on?

This issue is reproducible on both Linux and Windows.

What's the output of bazel info release?

release 3.4.1 and release 3.6.0 on Linux
release 3.5.0 on Windows

Have you found anything relevant by searching the web?

I tried to search the github issue database and stackoverflow/google.

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

Nope.

[LiyouZhou]

Is there a workaround for this?