1 files changed, 214 insertions, 0 deletions
diff --git a/pre_commit/languages/python.py b/pre_commit/languages/python.py
new file mode 100644
index 0000000..9f4bf69
--- /dev/null
+++ b/pre_commit/languages/python.py
@@ -0,0 +1,214 @@
+from __future__ import annotations
+
+import contextlib
+import functools
+import os
+import sys
+from collections.abc import Generator
+from collections.abc import Sequence
+
+import pre_commit.constants as C
+from pre_commit import lang_base
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
+from pre_commit.envcontext import UNSET
+from pre_commit.envcontext import Var
+from pre_commit.parse_shebang import find_executable
+from pre_commit.prefix import Prefix
+from pre_commit.util import CalledProcessError
+from pre_commit.util import cmd_output
+from pre_commit.util import cmd_output_b
+from pre_commit.util import win_exe
+
+ENVIRONMENT_DIR = 'py_env'
+run_hook = lang_base.basic_run_hook
+
+
+@functools.cache
+def _version_info(exe: str) -> str:
+    prog = 'import sys;print(".".join(str(p) for p in sys.version_info))'
+    try:
+        return cmd_output(exe, '-S', '-c', prog)[1].strip()
+    except CalledProcessError:
+        return f'<<error retrieving version from {exe}>>'
+
+
+def _read_pyvenv_cfg(filename: str) -> dict[str, str]:
+    ret = {}
+    with open(filename, encoding='UTF-8') as f:
+        for line in f:
+            try:
+                k, v = line.split('=')
+            except ValueError:  # blank line / comment / etc.
+                continue
+            else:
+                ret[k.strip()] = v.strip()
+    return ret
+
+
+def bin_dir(venv: str) -> str:
+    """On windows there's a different directory for the virtualenv"""
+    bin_part = 'Scripts' if sys.platform == 'win32' else 'bin'
+    return os.path.join(venv, bin_part)
+
+
+def get_env_patch(venv: str) -> PatchesT:
+    return (
+        ('PIP_DISABLE_PIP_VERSION_CHECK', '1'),
+        ('PYTHONHOME', UNSET),
+        ('VIRTUAL_ENV', venv),
+        ('PATH', (bin_dir(venv), os.pathsep, Var('PATH'))),
+    )
+
+
+def _find_by_py_launcher(
+        version: str,
+) -> str | None:  # pragma: no cover (windows only)
+    if version.startswith('python'):
+        num = version.removeprefix('python')
+        cmd = ('py', f'-{num}', '-c', 'import sys; print(sys.executable)')
+        env = dict(os.environ, PYTHONIOENCODING='UTF-8')
+        try:
+            return cmd_output(*cmd, env=env)[1].strip()
+        except CalledProcessError:
+            pass
+    return None
+
+
+def _find_by_sys_executable() -> str | None:
+    def _norm(path: str) -> str | None:
+        _, exe = os.path.split(path.lower())
+        exe, _, _ = exe.partition('.exe')
+        if exe not in {'python', 'pythonw'} and find_executable(exe):
+            return exe
+        return None
+
+    # On linux, I see these common sys.executables:
+    #
+    # system `python`: /usr/bin/python -> python2.7
+    # system `python2`: /usr/bin/python2 -> python2.7
+    # virtualenv v: v/bin/python (will not return from this loop)
+    # virtualenv v -ppython2: v/bin/python -> python2
+    # virtualenv v -ppython2.7: v/bin/python -> python2.7
+    # virtualenv v -ppypy: v/bin/python -> v/bin/pypy
+    for path in (sys.executable, os.path.realpath(sys.executable)):
+        exe = _norm(path)
+        if exe:
+            return exe
+    return None
+
+
+@functools.lru_cache(maxsize=1)
+def get_default_version() -> str:  # pragma: no cover (platform dependent)
+    # First attempt from `sys.executable` (or the realpath)
+    exe = _find_by_sys_executable()
+    if exe:
+        return exe
+
+    # Next try the `pythonX.X` executable
+    exe = f'python{sys.version_info[0]}.{sys.version_info[1]}'
+    if find_executable(exe):
+        return exe
+
+    if _find_by_py_launcher(exe):
+        return exe
+
+    # We tried!
+    return C.DEFAULT
+
+
+def _sys_executable_matches(version: str) -> bool:
+    if version == 'python':
+        return True
+    elif not version.startswith('python'):
+        return False
+
+    try:
+        info = tuple(int(p) for p in version.removeprefix('python').split('.'))
+    except ValueError:
+        return False
+
+    return sys.version_info[:len(info)] == info
+
+
+def norm_version(version: str) -> str | None:
+    if version == C.DEFAULT:  # use virtualenv's default
+        return None
+    elif _sys_executable_matches(version):  # virtualenv defaults to our exe
+        return None
+
+    if sys.platform == 'win32':  # pragma: no cover (windows)
+        version_exec = _find_by_py_launcher(version)
+        if version_exec:
+            return version_exec
+
+        # Try looking up by name
+        version_exec = find_executable(version)
+        if version_exec and version_exec != version:
+            return version_exec
+
+    # Otherwise assume it is a path
+    return os.path.expanduser(version)
+
+
+@contextlib.contextmanager
+def in_env(prefix: Prefix, version: str) -> Generator[None, None, None]:
+    envdir = lang_base.environment_dir(prefix, ENVIRONMENT_DIR, version)
+    with envcontext(get_env_patch(envdir)):
+        yield
+
+
+def health_check(prefix: Prefix, version: str) -> str | None:
+    envdir = lang_base.environment_dir(prefix, ENVIRONMENT_DIR, version)
+    pyvenv_cfg = os.path.join(envdir, 'pyvenv.cfg')
+
+    # created with "old" virtualenv
+    if not os.path.exists(pyvenv_cfg):
+        return 'pyvenv.cfg does not exist (old virtualenv?)'
+
+    exe_name = win_exe('python')
+    py_exe = prefix.path(bin_dir(envdir), exe_name)
+    cfg = _read_pyvenv_cfg(pyvenv_cfg)
+
+    if 'version_info' not in cfg:
+        return "created virtualenv's pyvenv.cfg is missing `version_info`"
+
+    # always use uncached lookup here in case we replaced an unhealthy env
+    virtualenv_version = _version_info.__wrapped__(py_exe)
+    if virtualenv_version != cfg['version_info']:
+        return (
+            f'virtualenv python version did not match created version:\n'
+            f'- actual version: {virtualenv_version}\n'
+            f'- expected version: {cfg["version_info"]}\n'
+        )
+
+    # made with an older version of virtualenv? skip `base-executable` check
+    if 'base-executable' not in cfg:
+        return None
+
+    base_exe_version = _version_info(cfg['base-executable'])
+    if base_exe_version != cfg['version_info']:
+        return (
+            f'base executable python version does not match created version:\n'
+            f'- base-executable version: {base_exe_version}\n'
+            f'- expected version: {cfg["version_info"]}\n'
+        )
+    else:
+        return None
+
+
+def install_environment(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> None:
+    envdir = lang_base.environment_dir(prefix, ENVIRONMENT_DIR, version)
+    venv_cmd = [sys.executable, '-mvirtualenv', envdir]
+    python = norm_version(version)
+    if python is not None:
+        venv_cmd.extend(('-p', python))
+    install_cmd = ('python', '-mpip', 'install', '.', *additional_dependencies)
+
+    cmd_output_b(*venv_cmd, cwd='/')
+    with in_env(prefix, version):
+        lang_base.setup_cmd(prefix, install_cmd)