Add support for python -m prek (#1686)

Related Issue: #1685

## Summary
prek can now be run with python -m prek in addition to the prek command,
matching common Python CLI tools like `black`, `ruff`, and `uv`.

## Motivation
- Consistency: Many Python tools support python -m <package>
- Virtual environments: Makes it clear which Python interpreter (and
venv) is used
- Scripts & CI: Explicit execution environment
- Tool integration: Some tools only support the `python -m` form

## Changes
- Add `python/prek/` package with `__init__.py` and `__main__.py`
- Set python-source = "python" in `pyproject.toml` so maturin includes
the Python package
- `__main__.`py invokes the prek binary next to the Python executable
(e.g. `.venv/bin/prek with .venv/bin/python`), falling back to PATH if
not found

---------

Co-authored-by: Jo <10510431+j178@users.noreply.github.com>

Author: uplsh580

pyproject.toml

@@ -31,6 +31,7 @@ build-backend = "maturin"
 bindings = "bin"
 manifest-path = "crates/prek/Cargo.toml"
 strip = true
+python-source = "python"
 include = [{ path = "licenses/*", format = ["wheel", "sdist"] }]
 
 [tool.rooster]

python/prek/__init__.py

@@ -0,0 +1,26 @@
+import os
+import shutil
+import subprocess
+import sys
+
+from ._find_prek import find_prek_bin
+
+def _run() -> None:
+    prek = find_prek_bin()
+
+    if sys.platform == "win32":
+        import subprocess
+
+        # Avoid emitting a traceback on interrupt
+        try:
+            completed_process = subprocess.run([prek, *sys.argv[1:]], env=env)
+        except KeyboardInterrupt:
+            sys.exit(2)
+
+        sys.exit(completed_process.returncode)
+    else:
+        os.execvp(prek, [prek, *sys.argv[1:]])
+
+
+if __name__ == "__main__":
+    _run()

python/prek/__main__.py

@@ -0,0 +1,121 @@
+# MIT License
+
+# Copyright (c) 2025 Astral Software Inc.
+
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+import os
+import sys
+import sysconfig
+
+
+class PrekNotFound(FileNotFoundError): ...
+
+
+def find_prek_bin() -> str:
+    """Return the prek binary path."""
+
+    prek_exe = "prek" + sysconfig.get_config_var("EXE")
+
+    targets = [
+        # The scripts directory for the current Python
+        sysconfig.get_path("scripts"),
+        # The scripts directory for the base prefix
+        sysconfig.get_path("scripts", vars={"base": sys.base_prefix}),
+        # Above the package root, e.g., from `pip install --prefix` or `uv run --with`
+        (
+            # On Windows, with module path `<prefix>/Lib/site-packages/prek`
+            _join(_matching_parents(_module_path(), "Lib/site-packages/prek"), "Scripts")
+            if sys.platform == "win32"
+            # On Unix,  with module path `<prefix>/lib/python3.13/site-packages/prek`
+            else _join(
+                _matching_parents(_module_path(), "lib/python*/site-packages/prek"), "bin"
+            )
+        ),
+        # Adjacent to the package root, e.g., from `pip install --target`
+        # with module path `<target>/prek`
+        _join(_matching_parents(_module_path(), "prek"), "bin"),
+        # The user scheme scripts directory, e.g., `~/.local/bin`
+        sysconfig.get_path("scripts", scheme=_user_scheme()),
+    ]
+
+    seen = []
+    for target in targets:
+        if not target:
+            continue
+        if target in seen:
+            continue
+        seen.append(target)
+        path = os.path.join(target, prek_exe)
+        if os.path.isfile(path):
+            return path
+
+    locations = "\n".join(f" - {target}" for target in seen)
+    raise PrekNotFound(
+        f"Could not find the prek binary in any of the following locations:\n{locations}\n"
+    )
+
+
+def _module_path() -> str | None:
+    path = os.path.dirname(__file__)
+    return path
+
+
+def _matching_parents(path: str | None, match: str) -> str | None:
+    """
+    Return the parent directory of `path` after trimming a `match` from the end.
+    The match is expected to contain `/` as a path separator, while the `path`
+    is expected to use the platform's path separator (e.g., `os.sep`). The path
+    components are compared case-insensitively and a `*` wildcard can be used
+    in the `match`.
+    """
+    from fnmatch import fnmatch
+
+    if not path:
+        return None
+    parts = path.split(os.sep)
+    match_parts = match.split("/")
+    if len(parts) < len(match_parts):
+        return None
+
+    if not all(
+        fnmatch(part, match_part)
+        for part, match_part in zip(reversed(parts), reversed(match_parts))
+    ):
+        return None
+
+    return os.sep.join(parts[: -len(match_parts)])
+
+
+def _join(path: str | None, *parts: str) -> str | None:
+    if not path:
+        return None
+    return os.path.join(path, *parts)
+
+
+def _user_scheme() -> str:
+    if sys.version_info >= (3, 10):
+        user_scheme = sysconfig.get_preferred_scheme("user")
+    elif os.name == "nt":
+        user_scheme = "nt_user"
+    elif sys.platform == "darwin" and sys._framework:  # ty: ignore[unresolved-attribute]
+        user_scheme = "osx_framework_user"
+    else:
+        user_scheme = "posix_user"
+    return user_scheme