[Bug]: py_pex_binary fails if binary target includes __main__.py

[AlexLamaison-UnlikelyAI]

What happened?

A py_pex_binary will fail to build if the binary it's given includes a file called main.py. Unfortunately, this is a common pattern because Gazelle uses it as a signal to create a binary target from the file.

Version

Development (host) and target OS/architectures:

Output of bazel --version: bazel 7.1.1

Version of the Aspect rules, or other relevant rules from your
WORKSPACE or MODULE.bazel file: v1.0.0

Language(s) and/or frameworks involved: Python 3.9, Bazel, Gazelle

How to reproduce

This is an example of the kind of binary target generated by Gazelle and the pex target using it:

py_binary(
    name = "gazelle_generated_main",
    srcs = ["__main__.py"],
    imports = [".."],
    main = "__main__.py",
)

py_pex_binary(
    name = "my_pex",
    binary = ":gazelle_generated_main",
)

This generates an error like:

Traceback (most recent call last):
  File "/home/alex/.cache/bazel/_bazel_alex/5413ef0fb20af199ccb77fe9356d6bd5/sandbox/processwrapper-sandbox/1552/execroot/_main/bazel-out/k8-opt-exec-ST-13d3ddad9198/bin/external/aspect_rules_py/py/tools/pex/pex.runfiles/aspect_rules_py/py/tools/pex/main.py", line 190, in <module>
    pex_builder.freeze(bytecode_compile=False)
  File "/home/alex/.cache/bazel/_bazel_alex/5413ef0fb20af199ccb77fe9356d6bd5/sandbox/processwrapper-sandbox/1552/execroot/_main/bazel-out/k8-opt-exec-ST-13d3ddad9198/bin/external/aspect_rules_py/py/tools/pex/pex.runfiles/.pex.venv/lib/python3.9/site-packages/pex/pex_builder.py", line 692, in freeze
    self._prepare_code()
  File "/home/alex/.cache/bazel/_bazel_alex/5413ef0fb20af199ccb77fe9356d6bd5/sandbox/processwrapper-sandbox/1552/execroot/_main/bazel-out/k8-opt-exec-ST-13d3ddad9198/bin/external/aspect_rules_py/py/tools/pex/pex.runfiles/.pex.venv/lib/python3.9/site-packages/pex/pex_builder.py", line 607, in _prepare_code
    self._chroot.write(
  File "/home/alex/.cache/bazel/_bazel_alex/5413ef0fb20af199ccb77fe9356d6bd5/sandbox/processwrapper-sandbox/1552/execroot/_main/bazel-out/k8-opt-exec-ST-13d3ddad9198/bin/external/aspect_rules_py/py/tools/pex/pex.runfiles/.pex.venv/lib/python3.9/site-packages/pex/common.py", line 623, in write
    self._tag(dst, label, compress)
  File "/home/alex/.cache/bazel/_bazel_alex/5413ef0fb20af199ccb77fe9356d6bd5/sandbox/processwrapper-sandbox/1552/execroot/_main/bazel-out/k8-opt-exec-ST-13d3ddad9198/bin/external/aspect_rules_py/py/tools/pex/pex.runfiles/.pex.venv/lib/python3.9/site-packages/pex/common.py", line 541, in _tag
    self._check_tag(fn, label, compress)
  File "/home/alex/.cache/bazel/_bazel_alex/5413ef0fb20af199ccb77fe9356d6bd5/sandbox/processwrapper-sandbox/1552/execroot/_main/bazel-out/k8-opt-exec-ST-13d3ddad9198/bin/external/aspect_rules_py/py/tools/pex/pex.runfiles/.pex.venv/lib/python3.9/site-packages/pex/common.py", line 521, in _check_tag
    raise self.ChrootTaggingException(
pex.common.Chroot.ChrootTaggingException: Trying to add __main__.py to fileset(main) but already in fileset(executable)!