trailing-whitespace: add option for custom chars to strip

pre_commit_hooks/trailing_whitespace_fixer.py

@@ -7,10 +7,15 @@ from typing import Optional
 from typing import Sequence
 
 
-def _fix_file(filename, is_markdown):  # type: (str, bool) -> bool
+def _fix_file(filename, is_markdown, chars_to_strip):
+    # type: (str, bool, Optional[bytes]) -> bool
     with open(filename, mode='rb') as file_processed:
         lines = file_processed.readlines()
-    newlines = [_process_line(line, is_markdown) for line in lines]
+    newlines = [
+        _process_line(line, is_markdown, chars_to_strip)
+        for line
+        in lines
+    ]
     if newlines != lines:
         with open(filename, mode='wb') as file_processed:
             for line in newlines:
@@ -20,7 +25,8 @@ def _fix_file(filename, is_markdown):  # type: (str, bool) -> bool
         return False
 
 
-def _process_line(line, is_markdown):  # type: (bytes, bool) -> bytes
+def _process_line(line, is_markdown, chars_to_strip):
+    # type: (bytes, bool, Optional[bytes]) -> bytes
     if line[-2:] == b'\r\n':
         eol = b'\r\n'
     elif line[-1:] == b'\n':
@@ -29,8 +35,8 @@ def _process_line(line, is_markdown):  # type: (bytes, bool) -> bytes
         eol = b''
     # preserve trailing two-space for non-blank lines in markdown files
     if is_markdown and (not line.isspace()) and line.endswith(b'  ' + eol):
-        return line.rstrip() + b'  ' + eol
-    return line.rstrip() + eol
+        return line.rstrip(chars_to_strip) + b'  ' + eol
+    return line.rstrip(chars_to_strip) + eol
 
 
 def main(argv=None):  # type: (Optional[Sequence[str]]) -> int
@@ -50,6 +56,11 @@ def main(argv=None):  # type: (Optional[Sequence[str]]) -> int
             'default: %(default)s'
         ),
     )
+    parser.add_argument(
+        '--chars',
+        help='The set of characters to strip from the end of lines.  '
+        'Defaults to all whitespace characters.',
+    )
     parser.add_argument('filenames', nargs='*', help='Filenames to fix')
     args = parser.parse_args(argv)
 
@@ -78,7 +89,11 @@ def main(argv=None):  # type: (Optional[Sequence[str]]) -> int
     for filename in args.filenames:
         _, extension = os.path.splitext(filename.lower())
         md = all_markdown or extension in md_exts
-        if _fix_file(filename, md):
+        if _fix_file(
+            filename,
+            md,
+            None if args.chars is None else bytes(args.chars, 'utf-8'),
+        ):
             print('Fixing {}'.format(filename))
             return_code = 1
     return return_code