Add types to pre-commit

pre_commit/languages/python.py

@@ -2,29 +2,40 @@ import contextlib
 import functools
 import os
 import sys
+from typing import Callable
+from typing import ContextManager
+from typing import Generator
+from typing import Optional
+from typing import Sequence
+from typing import Tuple
+from typing import TYPE_CHECKING
 
 import pre_commit.constants as C
 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.languages import helpers
 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 clean_path_on_failure
 from pre_commit.util import cmd_output
 from pre_commit.util import cmd_output_b
 
+if TYPE_CHECKING:
+    from pre_commit.repository import Hook
 
 ENVIRONMENT_DIR = 'py_env'
 
 
-def bin_dir(venv):
+def bin_dir(venv: str) -> str:
     """On windows there's a different directory for the virtualenv"""
     bin_part = 'Scripts' if os.name == 'nt' else 'bin'
     return os.path.join(venv, bin_part)
 
 
-def get_env_patch(venv):
+def get_env_patch(venv: str) -> PatchesT:
     return (
         ('PYTHONHOME', UNSET),
         ('VIRTUAL_ENV', venv),
@@ -32,7 +43,9 @@ def get_env_patch(venv):
     )
 
 
-def _find_by_py_launcher(version):  # pragma: no cover (windows only)
+def _find_by_py_launcher(
+        version: str,
+) -> Optional[str]:  # pragma: no cover (windows only)
     if version.startswith('python'):
         try:
             return cmd_output(
@@ -41,14 +54,16 @@ def _find_by_py_launcher(version):  # pragma: no cover (windows only)
             )[1].strip()
         except CalledProcessError:
             pass
+    return None
 
 
-def _find_by_sys_executable():
-    def _norm(path):
+def _find_by_sys_executable() -> Optional[str]:
+    def _norm(path: str) -> Optional[str]:
         _, exe = os.path.split(path.lower())
         exe, _, _ = exe.partition('.exe')
         if find_executable(exe) and exe not in {'python', 'pythonw'}:
             return exe
+        return None
 
     # On linux, I see these common sys.executables:
     #
@@ -66,7 +81,7 @@ def _find_by_sys_executable():
 
 
 @functools.lru_cache(maxsize=1)
-def get_default_version():  # pragma: no cover (platform dependent)
+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:
@@ -88,7 +103,7 @@ def get_default_version():  # pragma: no cover (platform dependent)
     return C.DEFAULT
 
 
-def _sys_executable_matches(version):
+def _sys_executable_matches(version: str) -> bool:
     if version == 'python':
         return True
     elif not version.startswith('python'):
@@ -102,7 +117,7 @@ def _sys_executable_matches(version):
     return sys.version_info[:len(info)] == info
 
 
-def norm_version(version):
+def norm_version(version: str) -> str:
     # first see if our current executable is appropriate
     if _sys_executable_matches(version):
         return sys.executable
@@ -126,14 +141,25 @@ def norm_version(version):
     return os.path.expanduser(version)
 
 
-def py_interface(_dir, _make_venv):
+def py_interface(
+        _dir: str,
+        _make_venv: Callable[[str, str], None],
+) -> Tuple[
+    Callable[[Prefix, str], ContextManager[None]],
+    Callable[[Prefix, str], bool],
+    Callable[['Hook', Sequence[str], bool], Tuple[int, bytes]],
+    Callable[[Prefix, str, Sequence[str]], None],
+]:
     @contextlib.contextmanager
-    def in_env(prefix, language_version):
+    def in_env(
+            prefix: Prefix,
+            language_version: str,
+    ) -> Generator[None, None, None]:
         envdir = prefix.path(helpers.environment_dir(_dir, language_version))
         with envcontext(get_env_patch(envdir)):
             yield
 
-    def healthy(prefix, language_version):
+    def healthy(prefix: Prefix, language_version: str) -> bool:
         with in_env(prefix, language_version):
             retcode, _, _ = cmd_output_b(
                 'python', '-c',
@@ -143,11 +169,19 @@ def py_interface(_dir, _make_venv):
             )
         return retcode == 0
 
-    def run_hook(hook, file_args, color):
+    def run_hook(
+            hook: 'Hook',
+            file_args: Sequence[str],
+            color: bool,
+    ) -> Tuple[int, bytes]:
         with in_env(hook.prefix, hook.language_version):
             return helpers.run_xargs(hook, hook.cmd, file_args, color=color)
 
-    def install_environment(prefix, version, additional_dependencies):
+    def install_environment(
+            prefix: Prefix,
+            version: str,
+            additional_dependencies: Sequence[str],
+    ) -> None:
         additional_dependencies = tuple(additional_dependencies)
         directory = helpers.environment_dir(_dir, version)
 
@@ -166,7 +200,7 @@ def py_interface(_dir, _make_venv):
     return in_env, healthy, run_hook, install_environment
 
 
-def make_venv(envdir, python):
+def make_venv(envdir: str, python: str) -> None:
     env = dict(os.environ, VIRTUALENV_NO_DOWNLOAD='1')
     cmd = (sys.executable, '-mvirtualenv', envdir, '-p', python)
     cmd_output_b(*cmd, env=env, cwd='/')