pathlib's Path("NUL:").resolve() throws an error on windows

[phillmac]

BPO	41536
Nosy	@pfmoore, @tjguk, @zware, @eryksun, @zooba, @phillmac

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-08-13.02:29:57.872>
labels = ['3.10', 'type-bug', '3.8', '3.9', 'OS-windows']
title = 'pathlib\'s Path("NUL:").resolve() throws an error on windows'
updated_at = <Date 2020-08-13.20:24:51.975>
user = 'https://github.com/phillmac'

bugs.python.org fields:

activity = <Date 2020-08-13.20:24:51.975>
actor = 'steve.dower'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Windows']
creation = <Date 2020-08-13.02:29:57.872>
creator = 'phillmac'
dependencies = []
files = []
hgrepos = []
issue_num = 41536
keywords = []
message_count = 2.0
messages = ['375289', '375342']
nosy_count = 6.0
nosy_names = ['paul.moore', 'tim.golden', 'zach.ware', 'eryksun', 'steve.dower', 'phillmac']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41536'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']

[phillmac]

I'm looking for the equivalent windows functionality to the posix `/dev/null` file, and I discovered `NUL:`

This snippet works on a windows OS, proving that it is indeed a writable file: Path('NUL:').write_text('abcd')

However, Path('NUL:').resolve() Throws an exception OSError: [WinError 87] The parameter is incorrect: 'NUL:'

Is this the expected behaviour? I.E. I should wrap the call to resolve() in a try...except?

If I catch all OSError types, how can I determine if it's a legitimate error or not?

E.G. Full console output:

    Python 3.7.1 (v3.7.1:260ec2c36a, Oct 20 2018, 14:57:15) [MSC v.1915 64 bit (AMD64)] on win32
    Type "help", "copyright", "credits" or "license" for more information.
    >>> from pathlib import Path
    >>> Path('NUL:')
    WindowsPath('NUL:')
    >>> Path('NUL:').write_text('abcd')
    4
    >>> Path('NUL:').resolve()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "C:\Program Files\Python37\lib\pathlib.py", line 1134, in resolve
        s = self._flavour.resolve(self, strict=strict)
      File "C:\Program Files\Python37\lib\pathlib.py", line 192, in resolve
        s = self._ext_to_normal(_getfinalpathname(s))
    OSError: [WinError 87] The parameter is incorrect: 'NUL:'

[zooba]

The trailing colon is unnecessary, and likely to cause more issues, but the same thing occurs for Path('NUL').resolve()

This is probably best handled as bpo-37517, where you'll find more background on the error messages.

But I believe that p.resolve(strict=True) should not raise when open(p) will succeed, and p.resolve(strict=False) should not raise when open(p) will succeed or raise a *NotFoundError subclass of OSError.