fix long path issue on Windows

[radoering]

Pull Request Check List

#10792 introduced an issue with long paths on Windows that causes sporadic test failures that look like:

[68](https://github.com/radoering/poetry/actions/runs/23705665774/job/69057056580#step:5:6069)
E           Attempting to write py.test.exe outside of the target directory
E           Target directory: C:\Users\runneradmin\AppData\Local\Temp\pytest-of-runneradmin\pytest-0\popen-gw0\test_execute_prints_warning_fo1\.venv\scripts
E           Target path: \\?\C:\Users\runneradmin\AppData\Local\Temp\pytest-of-runneradmin\pytest-0\popen-gw0\test_execute_prints_warning_fo1\.venv\scripts\py.test.exe

This change works around this issue. To be consistent, I replaced all uses of Path.is_relative_to() with the method that works around the issue.

• Added tests for changed code.
• Updated documentation for changed code.

Summary by Sourcery

Add a cross-platform path relativity helper and adopt it to avoid Windows long-path issues.

Bug Fixes:

• Prevent incorrect path relativity checks on Windows when long-path or UNC prefixes are involved, avoiding erroneous writes outside target directories and misclassification of environments.

Enhancements:

• Introduce a shared is_relative_to() helper in the compatibility module and use it across path-related checks in installation and environment management code.
• Include more detailed error information when attempting to write outside the wheel installation target directory.

Tests:

• Add unit tests for the is_relative_to() helper covering POSIX paths, Windows drive-letter paths, and Windows long-path and UNC-prefixed paths.

[sourcery-ai]

Reviewer's Guide

Introduces a compatibility helper for Path.is_relative_to that normalizes Windows long path prefixes and replaces direct Path.is_relative_to calls with this helper across the codebase, adding tests to verify behavior on POSIX and Windows paths (including long-path and UNC variants) and improving error diagnostics when wheel files attempt to write outside their installation target directory.

Sequence diagram for wheel_installer.write_to_fs path safety check with is_relative_to

sequenceDiagram
    participant WheelInstaller
    participant SchemeDict as scheme_dict
    participant Compat as _compat
    participant TargetDir as target_dir
    participant TargetPath as target_path

    WheelInstaller->>SchemeDict: lookup scheme
    SchemeDict-->>WheelInstaller: scheme_path
    WheelInstaller->>TargetDir: Path(scheme_path).resolve()
    WheelInstaller->>TargetPath: (target_dir / path).resolve()
    WheelInstaller->>Compat: is_relative_to(target_path, target_dir)
    Compat-->>WheelInstaller: is_relative
    alt target_path not relative to target_dir
        WheelInstaller-->>WheelInstaller: raise ValueError with path, target_dir, target_path
    else target_path inside target_dir
        WheelInstaller-->>WheelInstaller: proceed to write file
    end

Loading

File-Level Changes

Change	Details	Files
Add cross-platform is_relative_to helper that works around Windows long-path prefix issues and unit tests covering its behavior.	Introduce is_relative_to(path1, path2) in the compatibility module to normalize and strip Windows long path and UNC prefixes before delegating to Path.is_relative_to Implement Windows-specific prefix handling using string checks and reconstruction of normal and UNC paths Add parameterized tests for is_relative_to on relative, absolute POSIX, and Windows paths, including cases with and without long-path/UNC prefixes and platform-specific skipping.	src/poetry/utils/_compat.py tests/utils/test_compat.py
Replace direct uses of Path.is_relative_to with the new helper to avoid Windows long-path issues and slightly improve diagnostics for wheel installation.	Update wheel_installer.write_to_fs to use is_relative_to(target_path, target_dir) instead of Path.is_relative_to and expand the ValueError message with target directory and path for easier debugging Update env remove command to use is_relative_to when checking whether virtualenv paths are under the project directory Update python list command to use is_relative_to to determine if a Python installation is managed by Poetry based on its path Update Python manager to skip interpreters located in the active virtualenv using is_relative_to instead of Path.is_relative_to.	src/poetry/installation/wheel_installer.py src/poetry/console/commands/env/remove.py src/poetry/console/commands/python/list.py src/poetry/utils/env/python/manager.py

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[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="tests/utils/test_compat.py" line_range="12-26" />
<code_context>
+from poetry.utils._compat import is_relative_to
+
+
+@pytest.mark.parametrize(
+    ("path1", "path2", "expected"),
+    [
+        ("a", "a", True),
+        ("a/b", "a/b", True),
+        ("a/b", "a", True),
+        ("a", "a/b", False),
+        ("a/b/c/d", "a/b", True),
+        ("a/b", "a/b/c/d", False),
+    ],
+)
+def test_is_relative_to(path1: str, path2: str, expected: bool) -> None:
+    assert is_relative_to(Path(path1), Path(path2)) is expected
+
+
</code_context>
<issue_to_address>
**suggestion (testing):** Add Windows tests for paths on different drives / different UNC servers to avoid false positives

Current Windows parametrization only covers cases where `path1` and `path2` are on the same drive/server. To guard against false positives from the prefix-stripping logic, please add negative cases where roots differ, e.g.:

- `path1=r"C:\a\b"`, `path2=r"D:\a"` → `False`
- `path1=r"\\?\C:\a\b"`, `path2=r"D:\"` → `False`
- `path1=r"\\?\UNC\server1\a\b"`, `path2=r"\\?\UNC\server2\a"` → `False`
- `path1=r"\\server1\a\b"`, `path2=r"\\?\UNC\server2\a"` → `False`

These will help ensure unrelated roots are never treated as parents after prefix removal.

```suggestion
@pytest.mark.parametrize(
    ("path1", "path2", "expected"),
    [
        ("a", "a", True),
        ("a/b", "a/b", True),
        ("a/b", "a", True),
        ("a", "a/b", False),
        ("a/b/c/d", "a/b", True),
        ("a/b", "a/b/c/d", False),
    ],
)
def test_is_relative_to(path1: str, path2: str, expected: bool) -> None:
    assert is_relative_to(Path(path1), Path(path2)) is expected


@pytest.mark.skipif(sys.platform != "win32", reason="Windows-specific path semantics")
@pytest.mark.parametrize(
    ("path1", "path2", "expected"),
    [
        ("C:\\a\\b", "D:\\a", False),
        ("\\\\?\\C:\\a\\b", "D:\\", False),
        ("\\\\?\\UNC\\server1\\a\\b", "\\\\?\\UNC\\server2\\a", False),
        ("\\\\server1\\a\\b", "\\\\?\\UNC\\server2\\a", False),
    ],
)
def test_is_relative_to_windows_different_roots(
    path1: str, path2: str, expected: bool
) -> None:
    assert is_relative_to(Path(path1), Path(path2)) is expected
```
</issue_to_address>

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