3 files changed, 41 insertions, 6 deletions
diff --git a/pre_commit/commands/autoupdate.py b/pre_commit/commands/autoupdate.py
index 5a9a988..8c9fdd7 100644
--- a/pre_commit/commands/autoupdate.py
+++ b/pre_commit/commands/autoupdate.py
@@ -93,7 +93,7 @@ def _original_lines(
         retry: bool = False,
 ) -> Tuple[List[str], List[int]]:
     """detect `rev:` lines or reformat the file"""
-    with open(path) as f:
+    with open(path, newline='') as f:
         original = f.read()
 
     lines = original.splitlines(True)
@@ -126,7 +126,7 @@ def _write_new_config(path: str, rev_infos: List[Optional[RevInfo]]) -> None:
             comment = match[4]
         lines[idx] = f'{match[1]}rev:{match[2]}{new_rev}{comment}{match[5]}'
 
-    with open(path, 'w') as f:
+    with open(path, 'w', newline='') as f:
         f.write(''.join(lines))
 
 
diff --git a/pre_commit/commands/hook_impl.py b/pre_commit/commands/hook_impl.py
index 5ff4555..4843fc7 100644
--- a/pre_commit/commands/hook_impl.py
+++ b/pre_commit/commands/hook_impl.py
@@ -147,15 +147,44 @@ def _pre_push_ns(
     return None
 
 
+_EXPECTED_ARG_LENGTH_BY_HOOK = {
+    'commit-msg': 1,
+    'post-checkout': 3,
+    'pre-commit': 0,
+    'pre-merge-commit': 0,
+    'pre-push': 2,
+}
+
+
+def _check_args_length(hook_type: str, args: Sequence[str]) -> None:
+    if hook_type == 'prepare-commit-msg':
+        if len(args) < 1 or len(args) > 3:
+            raise SystemExit(
+                f'hook-impl for {hook_type} expected 1, 2, or 3 arguments '
+                f'but got {len(args)}: {args}',
+            )
+    elif hook_type in _EXPECTED_ARG_LENGTH_BY_HOOK:
+        expected = _EXPECTED_ARG_LENGTH_BY_HOOK[hook_type]
+        if len(args) != expected:
+            arguments_s = 'argument' if expected == 1 else 'arguments'
+            raise SystemExit(
+                f'hook-impl for {hook_type} expected {expected} {arguments_s} '
+                f'but got {len(args)}: {args}',
+            )
+    else:
+        raise AssertionError(f'unexpected hook type: {hook_type}')
+
+
 def _run_ns(
         hook_type: str,
         color: bool,
         args: Sequence[str],
         stdin: bytes,
 ) -> Optional[argparse.Namespace]:
+    _check_args_length(hook_type, args)
     if hook_type == 'pre-push':
         return _pre_push_ns(color, args, stdin)
-    elif hook_type in {'prepare-commit-msg', 'commit-msg'}:
+    elif hook_type in {'commit-msg', 'prepare-commit-msg'}:
         return _ns(hook_type, color, commit_msg_filename=args[0])
     elif hook_type in {'pre-merge-commit', 'pre-commit'}:
         return _ns(hook_type, color)
diff --git a/pre_commit/commands/run.py b/pre_commit/commands/run.py
index 2f74578..8c8401c 100644
--- a/pre_commit/commands/run.py
+++ b/pre_commit/commands/run.py
@@ -6,6 +6,7 @@ import os
 import re
 import subprocess
 import time
+import unicodedata
 from typing import Any
 from typing import Collection
 from typing import Dict
@@ -33,8 +34,13 @@ from pre_commit.util import EnvironT
 logger = logging.getLogger('pre_commit')
 
 
+def _len_cjk(msg: str) -> int:
+    widths = {'A': 1, 'F': 2, 'H': 1, 'N': 1, 'Na': 1, 'W': 2}
+    return sum(widths[unicodedata.east_asian_width(c)] for c in msg)
+
+
 def _start_msg(*, start: str, cols: int, end_len: int) -> str:
-    dots = '.' * (cols - len(start) - end_len - 1)
+    dots = '.' * (cols - _len_cjk(start) - end_len - 1)
     return f'{start}{dots}'
 
 
@@ -47,7 +53,7 @@ def _full_msg(
         use_color: bool,
         postfix: str = '',
 ) -> str:
-    dots = '.' * (cols - len(start) - len(postfix) - len(end_msg) - 1)
+    dots = '.' * (cols - _len_cjk(start) - len(postfix) - len(end_msg) - 1)
     end = color.format_color(end_msg, end_color, use_color)
     return f'{start}{dots}{postfix}{end}\n'
 
@@ -206,7 +212,7 @@ def _compute_cols(hooks: Sequence[Hook]) -> int:
         Hook name...(no files to check) Skipped
     """
     if hooks:
-        name_len = max(len(hook.name) for hook in hooks)
+        name_len = max(_len_cjk(hook.name) for hook in hooks)
     else:
         name_len = 0