compile_pip_requirements on Windows (GitHub workers) fails; bug is probably in the runfiles library

# 🐞 bug report

### Affected Rule

The issue is caused by the rule: compile\_pip\_requirements (but probably an issue in the runfiles library)

### Is this a regression?

Yes, the previous version in which this bug was not present was: 1.7.0

### Description

On the GitHub workers on MS-Windows, compile\_pip\_requirements rules fail with an error such as

```
File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\runfiles\runfiles.py", line 306, in Rlocation
source_repo = self.CurrentRepository(frame=2)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\runfiles\runfiles.py", line 384, in CurrentRepository
caller_runfiles_path = os.path.relpath(caller_path, self._python_runfiles_root)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "", line 777, in relpath
ValueError: path is on mount 'C:', start on mount 'D:'
```

## 🔬 Minimal Reproduction

https://github.com/phst/rules_python-bug-runfiles-windows

See e.g. the action logs at https://github.com/phst/rules_python-bug-runfiles-windows/actions/runs/22157518229

## 🔥 Exception or Error

==================== Test output for //:requirements.test:

Traceback (most recent call last):

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\_main\_requirements.test_stage2_bootstrap.py", line 499, in 

    main()

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\_main\_requirements.test_stage2_bootstrap.py", line 493, in main

    _run_py_path(main_filename, args=sys.argv[1:])

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\_main\_requirements.test_stage2_bootstrap.py", line 287, in _run_py_path

    runpy.run_path(main_filename, run_name="__main__")

  File "", line 291, in run_path

  File "", line 98, in _run_module_code

  File "", line 88, in _run_code

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\private\pypi\dependency_resolver\dependency_resolver.py", line 270, in 

    main()

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python++config+pypi__click\click\core.py", line 1157, in __call__

    return self.main(*args, **kwargs)

           ^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python++config+pypi__click\click\core.py", line 1078, in main

    rv = self.invoke(ctx)

         ^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python++config+pypi__click\click\core.py", line 1434, in invoke

    return ctx.invoke(self.callback, **ctx.params)

           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python++config+pypi__click\click\core.py", line 783, in invoke

    return __callback(*args, **kwargs)

           ^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\private\pypi\dependency_resolver\dependency_resolver.py", line 111, in main

    resolved_srcs = [_locate(bazel_runfiles, src) for src in srcs]

                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\private\pypi\dependency_resolver\dependency_resolver.py", line 111, in 

    resolved_srcs = [_locate(bazel_runfiles, src) for src in srcs]

                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\private\pypi\dependency_resolver\dependency_resolver.py", line 82, in _locate

    return bazel_runfiles.Rlocation(file)

           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\runfiles\runfiles.py", line 306, in Rlocation

    source_repo = self.CurrentRepository(frame=2)

                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "C:\Users\RUNNER~1\AppData\Local\Temp\Bazel.runfiles_flx90ick\runfiles\rules_python+\python\runfiles\runfiles.py", line 384, in CurrentRepository

    caller_runfiles_path = os.path.relpath(caller_path, self._python_runfiles_root)

                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

  File "", line 777, in relpath

ValueError: path is on mount 'C:', start on mount 'D:'

================================================================================

## 🌍 Your Environment

**Operating System:**

  

Windows

  

**Output of `bazel version`:**

  

Bazelisk version: 1.28.1

INFO: Invocation ID: 0c29aa33-c4d6-490c-ae50-a131af7e76a6

Build label: 9.0.0

Build target: @@//src/main/java/com/google/devtools/build/lib/bazel:BazelServer

Build time: Tue Jan 20 18:20:43 2026 (1768933243)

Build timestamp: 1768933243

Build timestamp as int: 1768933243


  

**Rules_python version:**

  

1.8.4

  

**Anything else relevant?**

See https://github.com/bazel-contrib/rules_python/pull/3086#issuecomment-3765803662 for the initial report.
Locally rolling back https://github.com/bazel-contrib/rules_python/commit/a506d774dd60eedf6fce94dcccd2c233553b06d4 fixes the issue.
Back-porting the fix to https://github.com/bazel-contrib/rules_python/issues/3579 locally does not fix the issue.

Commencez par python/runfiles/runfiles.py, en particulier CurrentRepository et Rlocation, puis examinez private/pypi/dependency_resolver/dependency_resolver.py et reproduisez l’échec de l’exemple Windows lié. Le travail est terminé lorsque compile_pip_requirements réussit sur les workers Windows de GitHub lorsque la racine de runfiles et l’appelant se trouvent sur des lecteurs différents, avec une couverture pour ce cas.

Rédigé par le modèle d'indexation à partir du texte de l'issue.