Add types to pre-commit

pre_commit/languages/helpers.py

@@ -1,33 +1,54 @@
 import multiprocessing
 import os
 import random
+from typing import Any
+from typing import List
+from typing import NoReturn
+from typing import Optional
+from typing import overload
+from typing import Sequence
+from typing import Tuple
+from typing import TYPE_CHECKING
 
 import pre_commit.constants as C
+from pre_commit.prefix import Prefix
 from pre_commit.util import cmd_output_b
 from pre_commit.xargs import xargs
 
+if TYPE_CHECKING:
+    from pre_commit.repository import Hook
+
 FIXED_RANDOM_SEED = 1542676186
 
 
-def run_setup_cmd(prefix, cmd):
+def run_setup_cmd(prefix: Prefix, cmd: Tuple[str, ...]) -> None:
     cmd_output_b(*cmd, cwd=prefix.prefix_dir)
 
 
-def environment_dir(ENVIRONMENT_DIR, language_version):
-    if ENVIRONMENT_DIR is None:
+@overload
+def environment_dir(d: None, language_version: str) -> None: ...
+@overload
+def environment_dir(d: str, language_version: str) -> str: ...
+
+
+def environment_dir(d: Optional[str], language_version: str) -> Optional[str]:
+    if d is None:
         return None
     else:
-        return f'{ENVIRONMENT_DIR}-{language_version}'
+        return f'{d}-{language_version}'
 
 
-def assert_version_default(binary, version):
+def assert_version_default(binary: str, version: str) -> None:
     if version != C.DEFAULT:
         raise AssertionError(
             f'For now, pre-commit requires system-installed {binary}',
         )
 
 
-def assert_no_additional_deps(lang, additional_deps):
+def assert_no_additional_deps(
+        lang: str,
+        additional_deps: Sequence[str],
+) -> None:
     if additional_deps:
         raise AssertionError(
             'For now, pre-commit does not support '
@@ -35,19 +56,23 @@ def assert_no_additional_deps(lang, additional_deps):
         )
 
 
-def basic_get_default_version():
+def basic_get_default_version() -> str:
     return C.DEFAULT
 
 
-def basic_healthy(prefix, language_version):
+def basic_healthy(prefix: Prefix, language_version: str) -> bool:
     return True
 
 
-def no_install(prefix, version, additional_dependencies):
+def no_install(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> NoReturn:
     raise AssertionError('This type is not installable')
 
 
-def target_concurrency(hook):
+def target_concurrency(hook: 'Hook') -> int:
     if hook.require_serial or 'PRE_COMMIT_NO_CONCURRENCY' in os.environ:
         return 1
     else:
@@ -61,8 +86,8 @@ def target_concurrency(hook):
                 return 1
 
 
-def _shuffled(seq):
-    """Deterministically shuffle identically under both py2 + py3."""
+def _shuffled(seq: Sequence[str]) -> List[str]:
+    """Deterministically shuffle"""
     fixed_random = random.Random()
     fixed_random.seed(FIXED_RANDOM_SEED, version=1)
 
@@ -71,7 +96,12 @@ def _shuffled(seq):
     return seq
 
 
-def run_xargs(hook, cmd, file_args, **kwargs):
+def run_xargs(
+        hook: 'Hook',
+        cmd: Tuple[str, ...],
+        file_args: Sequence[str],
+        **kwargs: Any,
+) -> Tuple[int, bytes]:
     # Shuffle the files so that they more evenly fill out the xargs partitions,
     # but do it deterministically in case a hook cares about ordering.
     file_args = _shuffled(file_args)