1 files changed, 71 insertions, 0 deletions
diff --git a/pre_commit_hooks/end_of_file_fixer.py b/pre_commit_hooks/end_of_file_fixer.py
new file mode 100644
index 0000000..a30dce9
--- /dev/null
+++ b/pre_commit_hooks/end_of_file_fixer.py
@@ -0,0 +1,71 @@
+from __future__ import annotations
+
+import argparse
+import os
+from typing import IO
+from typing import Sequence
+
+
+def fix_file(file_obj: IO[bytes]) -> int:
+    # Test for newline at end of file
+    # Empty files will throw IOError here
+    try:
+        file_obj.seek(-1, os.SEEK_END)
+    except OSError:
+        return 0
+    last_character = file_obj.read(1)
+    # last_character will be '' for an empty file
+    if last_character not in {b'\n', b'\r'} and last_character != b'':
+        # Needs this seek for windows, otherwise IOError
+        file_obj.seek(0, os.SEEK_END)
+        file_obj.write(b'\n')
+        return 1
+
+    while last_character in {b'\n', b'\r'}:
+        # Deal with the beginning of the file
+        if file_obj.tell() == 1:
+            # If we've reached the beginning of the file and it is all
+            # linebreaks then we can make this file empty
+            file_obj.seek(0)
+            file_obj.truncate()
+            return 1
+
+        # Go back two bytes and read a character
+        file_obj.seek(-2, os.SEEK_CUR)
+        last_character = file_obj.read(1)
+
+    # Our current position is at the end of the file just before any amount of
+    # newlines.  If we find extraneous newlines, then backtrack and trim them.
+    position = file_obj.tell()
+    remaining = file_obj.read()
+    for sequence in (b'\n', b'\r\n', b'\r'):
+        if remaining == sequence:
+            return 0
+        elif remaining.startswith(sequence):
+            file_obj.seek(position + len(sequence))
+            file_obj.truncate()
+            return 1
+
+    return 0
+
+
+def main(argv: Sequence[str] | None = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help='Filenames to fix')
+    args = parser.parse_args(argv)
+
+    retv = 0
+
+    for filename in args.filenames:
+        # Read as binary so we can read byte-by-byte
+        with open(filename, 'rb+') as file_obj:
+            ret_for_file = fix_file(file_obj)
+            if ret_for_file:
+                print(f'Fixing {filename}')
+            retv |= ret_for_file
+
+    return retv
+
+
+if __name__ == '__main__':
+    raise SystemExit(main())