--include-paths is documented as a path-list option, so it should be parsed using the current platform's path separator. However, the implementation currently splits it with a hard-coded :, which incorrectly splits Windows drive-letter paths such as C:\....

PR summary

Fixes #31933.

What Problem This Solves

f2py --include-paths is documented as a path-list option whose entries should be separated with the platform path separator (os.pathsep): : on POSIX and ; on Windows. The current parser instead splits --include-paths and the deprecated --include_paths form on : unconditionally.

That is incorrect for native Windows paths, because a drive-letter path such as C:\inc1 contains : as part of the path itself. As a result, the parser can split a single Windows include directory into invalid pieces before F2PY passes the include path list downstream.

Changes

This PR updates the --include-paths and deprecated --include_paths parser branch to split on os.pathsep. It leaves -I <path> unchanged as a single include-directory option.

 if option_string in {--include-paths, --include_paths}:
-    include_paths_set.update(values.split(':'))
+    include_paths_set.update(values.split(os.pathsep))
 else:
     include_paths_set.add(values)

The change is intentionally scoped to F2PY CLI option parsing and the corresponding help/docs text. It does not change Fortran include-file resolution, Meson/backend include propagation, or compiler -I handling.

The PR also updates the CLI help/docs wording from the POSIX-looking <path1>:<path2> form to the platform-neutral <path1><pathsep><path2> form, and adds parser-level regression coverage for Windows-style drive-letter paths and Windows-style path lists.

Evidence

Validation performed locally:

• Parser-only check against the patched numpy/f2py/f2py2e.py definitions:
  • --include-paths C:\inc1 remains one path
  • --include-paths C:\inc1;D:\inc2 splits into two paths when os.pathsep == ;
  • deprecated --include_paths follows the same path-list behavior
  • -I C:\inc1;D:\inc2 remains one single path
• git diff --check

Remote validation:

• CI passed on this PR, including lint, Windows, Linux, macOS, wheel builds, MyPy, stubtest, and CircleCI docs/build checks.

First time committer introduction

This change was found while reviewing F2PY path handling on Windows, especially the difference between path-list parsing for --include-paths and single-path handling for -I.

AI Disclosure

AI assisted with identifying the issue and drafting the patch. The final code was reviewed and submitted by the human contributor.