mypy passes with check_untyped_defs

pre_commit/languages/all.py

@@ -1,3 +1,6 @@
+from typing import Any
+from typing import Dict
+
 from pre_commit.languages import conda
 from pre_commit.languages import docker
 from pre_commit.languages import docker_image
@@ -13,6 +16,7 @@ from pre_commit.languages import script
 from pre_commit.languages import swift
 from pre_commit.languages import system
 
+
 # A language implements the following constant and functions in its module:
 #
 # # Use None for no environment
@@ -49,7 +53,7 @@ from pre_commit.languages import system
 #         (returncode, output)
 #     """
 
-languages = {
+languages: Dict[str, Any] = {
     'conda': conda,
     'docker': docker,
     'docker_image': docker_image,

pre_commit/languages/conda.py

@@ -2,6 +2,7 @@ import contextlib
 import os
 
 from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import SubstitutionT
 from pre_commit.envcontext import UNSET
 from pre_commit.envcontext import Var
 from pre_commit.languages import helpers
@@ -18,7 +19,7 @@ def get_env_patch(env):
     # they can be in $CONDA_PREFIX/bin, $CONDA_PREFIX/Library/bin,
     # $CONDA_PREFIX/Scripts and $CONDA_PREFIX. Whereas the latter only
     # seems to be used for python.exe.
-    path = (os.path.join(env, 'bin'), os.pathsep, Var('PATH'))
+    path: SubstitutionT = (os.path.join(env, 'bin'), os.pathsep, Var('PATH'))
     if os.name == 'nt':  # pragma: no cover (platform specific)
         path = (env, os.pathsep) + path
         path = (os.path.join(env, 'Scripts'), os.pathsep) + path

pre_commit/languages/docker.py

@@ -1,5 +1,6 @@
 import hashlib
 import os
+from typing import Tuple
 
 import pre_commit.constants as C
 from pre_commit import five
@@ -42,7 +43,7 @@ def assert_docker_available():  # pragma: windows no cover
 def build_docker_image(prefix, **kwargs):  # pragma: windows no cover
     pull = kwargs.pop('pull')
     assert not kwargs, kwargs
-    cmd = (
+    cmd: Tuple[str, ...] = (
         'docker', 'build',
         '--tag', docker_tag(prefix),
         '--label', PRE_COMMIT_LABEL,

pre_commit/languages/python.py

@@ -1,4 +1,5 @@
 import contextlib
+import functools
 import os
 import sys
 
@@ -64,7 +65,8 @@ def _find_by_sys_executable():
     return None
 
 
-def _get_default_version():  # pragma: no cover (platform dependent)
+@functools.lru_cache(maxsize=1)
+def get_default_version():  # pragma: no cover (platform dependent)
     # First attempt from `sys.executable` (or the realpath)
     exe = _find_by_sys_executable()
     if exe:
@@ -86,15 +88,6 @@ def _get_default_version():  # pragma: no cover (platform dependent)
     return C.DEFAULT
 
 
-def get_default_version():
-    # TODO: when dropping python2, use `functools.lru_cache(maxsize=1)`
-    try:
-        return get_default_version.cached_version
-    except AttributeError:
-        get_default_version.cached_version = _get_default_version()
-        return get_default_version()
-
-
 def _sys_executable_matches(version):
     if version == 'python':
         return True

pre_commit/languages/ruby.py

@@ -5,6 +5,7 @@ import tarfile
 
 import pre_commit.constants as C
 from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import PatchesT
 from pre_commit.envcontext import Var
 from pre_commit.languages import helpers
 from pre_commit.util import CalledProcessError
@@ -18,7 +19,7 @@ healthy = helpers.basic_healthy
 
 
 def get_env_patch(venv, language_version):  # pragma: windows no cover
-    patches = (
+    patches: PatchesT = (
         ('GEM_HOME', os.path.join(venv, 'gems')),
         ('RBENV_ROOT', venv),
         ('BUNDLE_IGNORE_CONFIG', '1'),

pre_commit/languages/rust.py

@@ -1,5 +1,7 @@
 import contextlib
 import os.path
+from typing import Set
+from typing import Tuple
 
 import toml
 
@@ -71,7 +73,7 @@ def install_environment(prefix, version, additional_dependencies):
         _add_dependencies(prefix.path('Cargo.toml'), lib_deps)
 
     with clean_path_on_failure(directory):
-        packages_to_install = {('--path', '.')}
+        packages_to_install: Set[Tuple[str, ...]] = {('--path', '.')}
         for cli_dep in cli_deps:
             cli_dep = cli_dep[len('cli:'):]
             package, _, version = cli_dep.partition(':')