Make hermetic interpreters compatible to disallow_empty_glob

[martis42]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature (please, look at the "Scope of the project" section in the README.md file)
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Using Bazel CLI option incompatible_disallow_empty_glob is not compatible with using a hermetic interpreter offered by rules_python.

It causes the error (exemplary for a Linux host):

ERROR: Traceback (most recent call last):
	File "<path_to_bazel_out>/external/python3_10_x86_64-unknown-linux-gnu/BUILD.bazel", line 9, column 16, in <toplevel>
		srcs = glob(
Error in glob: glob pattern '*.exe' didn't match anything, but allow_empty is set to False (the default value of allow_empty can be set with --incompatible_disallow_empty_glob).

Issue Number: N/A

What is the underlying problem

A single filegroup is used to aggregate the interpreter files. Its platform specific regex patterns are not compatible to the flag --incompatible_disallow_empty_glob which forbids any pattern to return an empty list. For example, on a Linux host the "*.exe", pattern will be empty.

Reproducing

Minimal workspace for reproducing the problem.

WORKSPACE

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
    name = "rules_python",
    sha256 = "a3a6e99f497be089f81ec082882e40246bfd435f52f4e82f37e89449b04573f6",
    strip_prefix = "rules_python-0.10.2",
    url = "https://github.com/bazelbuild/rules_python/archive/refs/tags/0.10.2.tar.gz",
)

load("@rules_python//python:repositories.bzl", "python_register_toolchains")
python_register_toolchains(
    name = "python3_10",
    python_version = "3.10",
)

BUILD

load("@rules_python//python:defs.bzl", "py_binary")

py_binary(
    name = "foo",
    srcs = ["foo.py"],
)

foo.py

import sys
print(sys.version)

Command to generate the error:
bazel run --incompatible_disallow_empty_glob //:foo

What is the new behavior?

One can utilize flag incompatible_disallow_empty_glob while using a hermetic Python interpreter offered by rules_python.

Does this PR introduce a breaking change?

• Yes
• No

Other information

What alternatives have been considered.

We could also introduce separate filegroups for the different platforms and use an alias with a platforms based select statement to provide the correct one to the user.
However, given how unlikely it is that an interpreter without files is referenced by rules_python and this is not discovered in any test, we should use the straight forward solution offered in this PR instead of introducing this additional complexity.

[thundergolfer]

Fine with this simple approach. Seems there's not really a clean way to partition the patterns into required and maybe like so:

filegroup(
    name = "files",
    srcs = glob(
        include = [
            "bin/**",
            ...
        ],
        exclude = [
            "**/* *", # Bazel does not support spaces in file names.
        ],
        allow_empty = False,
    ) + glob(
        # Platform-specific files.
        include = [
            ...
        ],
        allow_empty = True,
    ),
)

[martis42]

@thundergolfer
I incorporated the comment suggested by you and rebased the PR. Anything else required from my side for this to merge?