Add types to pre-commit

pre_commit/output.py

@@ -1,19 +1,22 @@
 import contextlib
 import sys
+from typing import IO
+from typing import Optional
+from typing import Union
 
 from pre_commit import color
 from pre_commit import five
 
 
 def get_hook_message(
-        start,
-        postfix='',
-        end_msg=None,
-        end_len=0,
-        end_color=None,
-        use_color=None,
-        cols=80,
-):
+        start: str,
+        postfix: str = '',
+        end_msg: Optional[str] = None,
+        end_len: int = 0,
+        end_color: Optional[str] = None,
+        use_color: Optional[bool] = None,
+        cols: int = 80,
+) -> str:
     """Prints a message for running a hook.
 
     This currently supports three approaches:
@@ -44,16 +47,13 @@ def get_hook_message(
     )
     start...........................................................postfix end
     """
-    if bool(end_msg) == bool(end_len):
-        raise ValueError('Expected one of (`end_msg`, `end_len`)')
-    if end_msg is not None and (end_color is None or use_color is None):
-        raise ValueError(
-            '`end_color` and `use_color` are required with `end_msg`',
-        )
-
     if end_len:
+        assert end_msg is None, end_msg
         return start + '.' * (cols - len(start) - end_len - 1)
     else:
+        assert end_msg is not None
+        assert end_color is not None
+        assert use_color is not None
         return '{}{}{}{}\n'.format(
             start,
             '.' * (cols - len(start) - len(postfix) - len(end_msg) - 1),
@@ -62,15 +62,16 @@ def get_hook_message(
         )
 
 
-stdout_byte_stream = getattr(sys.stdout, 'buffer', sys.stdout)
-
-
-def write(s, stream=stdout_byte_stream):
+def write(s: str, stream: IO[bytes] = sys.stdout.buffer) -> None:
     stream.write(five.to_bytes(s))
     stream.flush()
 
 
-def write_line(s=None, stream=stdout_byte_stream, logfile_name=None):
+def write_line(
+        s: Union[None, str, bytes] = None,
+        stream: IO[bytes] = sys.stdout.buffer,
+        logfile_name: Optional[str] = None,
+) -> None:
     with contextlib.ExitStack() as exit_stack:
         output_streams = [stream]
         if logfile_name: