chore: unify git path strip

Author: RonnyPfannschmidt

src/setuptools_scm/_compat.py

@@ -0,0 +1,65 @@
+"""Compatibility utilities for cross-platform functionality."""
+
+from __future__ import annotations
+
+
+def normalize_path_for_assertion(path: str) -> str:
+    """Normalize path separators for cross-platform assertions.
+
+    On Windows, this converts backslashes to forward slashes to ensure
+    path comparisons work correctly. On other platforms, returns the path unchanged.
+    The length of the string is not changed by this operation.
+
+    Args:
+        path: The path string to normalize
+
+    Returns:
+        The path with normalized separators
+    """
+    return path.replace("\\", "/")
+
+
+def strip_path_suffix(
+    full_path: str, suffix_path: str, error_msg: str | None = None
+) -> str:
+    """Strip a suffix from a path, with cross-platform path separator handling.
+
+    This function first normalizes path separators for Windows compatibility,
+    then asserts that the full path ends with the suffix, and finally returns
+    the path with the suffix removed. This is the common pattern used for
+    computing parent directories from git output.
+
+    Args:
+        full_path: The full path string
+        suffix_path: The suffix path to strip from the end
+        error_msg: Optional custom error message for the assertion
+
+    Returns:
+        The prefix path with the suffix removed
+
+    Raises:
+        AssertionError: If the full path doesn't end with the suffix
+    """
+    normalized_full = normalize_path_for_assertion(full_path)
+
+    if error_msg:
+        assert normalized_full.endswith(suffix_path), error_msg
+    else:
+        assert normalized_full.endswith(suffix_path), (
+            f"Path assertion failed: {full_path!r} does not end with {suffix_path!r}"
+        )
+
+    return full_path[: -len(suffix_path)]
+
+
+# Legacy aliases for backward compatibility during transition
+def assert_path_endswith(
+    full_path: str, suffix_path: str, error_msg: str | None = None
+) -> None:
+    """Legacy alias - use strip_path_suffix instead."""
+    strip_path_suffix(full_path, suffix_path, error_msg)
+
+
+def compute_path_prefix(full_path: str, suffix_path: str) -> str:
+    """Legacy alias - use strip_path_suffix instead."""
+    return strip_path_suffix(full_path, suffix_path)

src/setuptools_scm/_file_finders/git.py

@@ -39,11 +39,9 @@ def _git_toplevel(path: str) -> str | None:
             # ``cwd`` is absolute path to current working directory.
             # the below method removes the length of ``out`` from
             # ``cwd``, which gives the git toplevel
-            assert cwd.replace("\\", "/").endswith(out), f"cwd={cwd!r}\nout={out!r}"
-            # In windows cwd contains ``\`` which should be replaced by ``/``
-            # for this assertion to work. Length of string isn't changed by replace
-            # ``\\`` is just and escape for `\`
-            out = cwd[: -len(out)]
+            from .._compat import strip_path_suffix
+
+            out = strip_path_suffix(cwd, out, f"cwd={cwd!r}\nout={out!r}")
         log.debug("find files toplevel %s", out)
         return norm_real(out)
     except subprocess.CalledProcessError:

src/setuptools_scm/git.py

@@ -93,11 +93,9 @@ def from_potential_worktree(cls, wd: _t.PathT) -> GitWorkdir | None:
             real_wd = os.fspath(wd)
         else:
             str_wd = os.fspath(wd)
-            assert str_wd.replace("\\", "/").endswith(real_wd)
-            # In windows wd contains ``\`` which should be replaced by ``/``
-            # for this assertion to work.  Length of string isn't changed by replace
-            # ``\\`` is just and escape for `\`
-            real_wd = str_wd[: -len(real_wd)]
+            from ._compat import strip_path_suffix
+
+            real_wd = strip_path_suffix(str_wd, real_wd)
         log.debug("real root %s", real_wd)
         if not samefile(real_wd, wd):
             return None

testing/test_compat.py

@@ -0,0 +1,73 @@
+"""Test compatibility utilities."""
+
+from __future__ import annotations
+
+import pytest
+
+from setuptools_scm._compat import normalize_path_for_assertion
+from setuptools_scm._compat import strip_path_suffix
+
+
+def test_normalize_path_for_assertion() -> None:
+    """Test path normalization for assertions."""
+    # Unix-style paths should remain unchanged
+    assert normalize_path_for_assertion("/path/to/file") == "/path/to/file"
+
+    # Windows-style paths should be normalized
+    assert normalize_path_for_assertion(r"C:\path\to\file") == "C:/path/to/file"
+    assert normalize_path_for_assertion(r"path\to\file") == "path/to/file"
+
+    # Mixed paths should be normalized
+    assert normalize_path_for_assertion(r"C:\path/to\file") == "C:/path/to/file"
+
+    # Already normalized paths should remain unchanged
+    assert normalize_path_for_assertion("path/to/file") == "path/to/file"
+
+
+def test_strip_path_suffix_success() -> None:
+    """Test successful path suffix stripping."""
+    # Unix-style paths
+    assert strip_path_suffix("/home/user/project", "project") == "/home/user/"
+    assert (
+        strip_path_suffix("/home/user/project/subdir", "project/subdir")
+        == "/home/user/"
+    )
+
+    # Windows-style paths
+    assert (
+        strip_path_suffix("C:\\Users\\user\\project", "project") == "C:\\Users\\user\\"
+    )
+    assert (
+        strip_path_suffix("C:\\Users\\user\\project\\subdir", "project/subdir")
+        == "C:\\Users\\user\\"
+    )
+
+    # Mixed paths should work due to normalization
+    assert (
+        strip_path_suffix("C:\\Users\\user\\project", "project") == "C:\\Users\\user\\"
+    )
+    assert strip_path_suffix("/home/user/project", "project") == "/home/user/"
+
+    # Edge cases
+    assert strip_path_suffix("project", "project") == ""
+    assert strip_path_suffix("/project", "project") == "/"
+
+
+def test_strip_path_suffix_failure() -> None:
+    """Test failed path suffix stripping."""
+    with pytest.raises(AssertionError, match="Path assertion failed"):
+        strip_path_suffix("/home/user/project", "other")
+
+    with pytest.raises(AssertionError, match="Custom error"):
+        strip_path_suffix("/home/user/project", "other", "Custom error")
+
+
+def test_integration_example() -> None:
+    """Test the integration pattern used in the codebase."""
+    # Simulate the pattern used in git.py and _file_finders/git.py
+    full_path = r"C:\\Users\\user\\project\\subdir"
+    suffix = "subdir"
+
+    # Now this is a single operation
+    prefix = strip_path_suffix(full_path, suffix)
+    assert prefix == r"C:\\Users\\user\\project\\"