[issue33105] os.path.isfile returns false on Windows when file path is longer than 260 characters

[Eryk Sun]

Eryk Sun <eryksun at gmail.com> added the comment:

> If you use os.listdir() on the networked folder, the log file 
> will come up.

Querying a file's parent directory (e.g. via os.scandir in Python 3) can provide a basic stat (i.e. attributes, reparse tag, size, and timestamps) when opening the file directly fails. Currently the os.[l]stat implementation in Python 3 falls back on querying the directory for ERROR_ACCESS_DENIED (e.g. due to a file's security, delete disposition, or an exclusive open) and ERROR_SHARING_VIOLATION (e.g. a system paging file). 

This could be expanded to ERROR_PATH_NOT_FOUND, which among other reasons, can indicate the path was too long if long-path support isn't available. This would expand the reach to all files in which the path of the parent directory is less than MAX_PATH. This would keep os.[l]stat consistent with os.listdir and os.scandir, which it currently is not. For example:

    >>> parent_path, filename = os.path.split(path)
    >>> len(path), len(parent_path), filename
    (264, 255, 'spam.txt')

    >>> os.path.exists(path)
    False
    >>> entry = next(os.scandir(parent_path))
    >>> entry.name
    'spam.txt'
    >>> entry.stat()
    os.stat_result(st_mode=33206, st_ino=0, st_dev=0, st_nlink=0,
                   st_uid=0, st_gid=0, st_size=0, st_atime=1521507879,
                   st_mtime=1521507879, st_ctime=1521507879)

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components: +Windows
stage:  -> needs patch
versions: +Python 3.8

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<https://bugs.python.org/issue33105>
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