[Bug]: py_binary expression expands to more than one file

[keith]

What happened?

Using rules_python's py_binary like this:

py_binary(
    name = "upstream_py_binary",
    srcs = ["say.py"],
    main = "say.py",
)

py_binary(
    name = "upstream_py_binary2",
    srcs = ["say.py"],
    main = "say.py",
    data = [":upstream_py_binary"],
    env = {"FOO": "$(execpath :upstream_py_binary)"},
)

Works fine, but if you do the same with rules_py's py_binary, you get this error:

ERROR: /home/ubuntu/dev/bazelbuild/rules_py/examples/py_binary/BUILD.bazel:9:10: in py_binary rule //examples/py_binary:py_binary2: label '//examples/py_binary:py_binary' in $(location) expression expands to more than one file, please use $(locations //examples/py_binary:py_binary) instead.  Files (at most 5 shown) are: [bazel-out/aarch64-fastbuild/bin/examples/py_binary/py_binary, bazel-out/aarch64-fastbuild/bin/examples/py_binary/py_binary.venv.pth, examples/py_binary/say.py]

Version

Development (host) and target OS/architectures: ubuntu 22.04

Output of bazel --version: bazel 7.4.0

Version of the Aspect rules, or other relevant rules from your WORKSPACE or MODULE.bazel file: see repro case below

How to reproduce

On this branch: #456

bazel build :upstream_py_binary2 works fine
bazel build :py_binary2 fails with the above error

Any other information?

No response

[mattem]

The reason this works in rules_python is that they use an exposed internal method to expand the files, rather than the one on ctx, all Bazel built-in rules exhibit this behavior, iirc there's an open issue upstream for it.

That being said, it likely makes sense to remove the other outputs from files on DefaultInfo.

[keith]

Will removing those extra files not break some other workflow?

[keith]

here's that change if not: #467

[keith]

maybe bazelbuild/bazel#24690 is the better solve here

[thesayyn]

Yes, this should be fixed in Bazel. I wanted to send a patch myself, but never got time.