Add check for illegal Widnows names

Fixes #589

pre_commit_hooks/check_illegal_windows_names.py

@@ -0,0 +1,66 @@
+import argparse
+import os.path
+from typing import Iterable
+from typing import Iterator
+from typing import Optional
+from typing import Sequence
+from typing import Set
+
+from pre_commit_hooks.util import added_files
+
+
+def lower_set(iterable: Iterable[str]) -> Set[str]:
+    return {x.lower() for x in iterable}
+
+
+def parents(file: str) -> Iterator[str]:
+    file = os.path.dirname(file)
+    while file:
+        yield file
+        file = os.path.dirname(file)
+
+
+def directories_for(files: Set[str]) -> Set[str]:
+    return {parent for file in files for parent in parents(file)}
+
+
+# https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file
+ILLEGAL_NAMES = {
+    'CON',
+    'PRN',
+    'AUX',
+    'NUL',
+    *(f'COM{i}' for i in range(1, 10)),
+    *(f'LPT{i}' for i in range(1, 10)),
+}
+
+
+def find_illegal_windows_names(filenames: Sequence[str]) -> int:
+    relevant_files = set(filenames) | added_files()
+    relevant_files |= directories_for(relevant_files)
+    retv = 0
+
+    for filename in relevant_files:
+        root = os.path.basename(filename)
+        while '.' in root:
+            root, _ = os.path.splitext(root)
+        if root.lower() in lower_set(ILLEGAL_NAMES):
+            print(f'Illegal name {filename}')
+            retv = 1
+    return retv
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        'filenames', nargs='*',
+        help='Filenames pre-commit believes are changed.',
+    )
+
+    args = parser.parse_args(argv)
+
+    return find_illegal_windows_names(args.filenames)
+
+
+if __name__ == '__main__':
+    exit(main())