mdformat._util.atomic_write fails if dir isn't writeable

[guykisel]

Describe the bug

context
I'm running mdformat on a directory of markdown docs in a perforce repo. In perforce, everything in a repo defaults to read-only, and only becomes writeable when checked out. Normally this should be fine, because I'm running mdformat on files I've checked out. However, the atomic_write function creates a temp dir in the current path, which in this case is not writeable unless I've explicitly checked it out.

expectation
I expect atomic_write to fall back to creating the temp dir in one of the default paths used by tempfile.gettempdir() as described at https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir or perhaps alternatively to give up on atomic writes and just do a best-effort?

bug
atomic_write fails with a permission error :(

> mdformat .
Traceback (most recent call last):
  File "D:\prj\python\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Users\user\AppData\Local\pypoetry\Cache\virtualenvs\docs\Scripts\mdformat.exe\__main__.py", line 7, in <module>
  File "C:\Users\user\AppData\Local\pypoetry\Cache\virtualenvs\docs\lib\site-packages\mdformat\__main__.py", line 8, in run
    exit_code = mdformat._cli.run(sys.argv[1:])
  File "C:\Users\user\AppData\Local\pypoetry\Cache\virtualenvs\docs\lib\site-packages\mdformat\_cli.py", line 114, in run
    atomic_write(path, formatted_str, newline)
  File "C:\Users\user\AppData\Local\pypoetry\Cache\virtualenvs\docs\lib\site-packages\mdformat\_util.py", line 115, in atomic_write
    os.replace(tmp_path, path)
PermissionError: [WinError 5] Access is denied: 'D:\\prj\\docs\\tmpyw2fgxhp' -> 'D:\\prj\\docs\\README.md'
Error: Sequence aborted after failed subtask 'mdformat'

problem
This makes using mdformat with perforce slightly more difficult. It's not a blocker, just mildly annoying.

Reproduce the bug

1. Set up a perforce repo
2. Create a dir with markdown files in the repo
3. Check out some of the files in a changelist, but not the parent dir
4. Run mdformat on the files

List your environment

Python 3.9.1

> python -m pip freeze
attrs==22.2.0
CacheControl==0.12.11
certifi==2022.12.7
charset-normalizer==3.0.1
cleo==2.0.1
crashtest==0.4.1
distlib==0.3.6
dulwich==0.20.50
filelock==3.9.0
html5lib==1.1
idna==3.4
importlib-metadata==4.13.0
jaraco.classes==3.2.3
jsonschema==4.17.3
keyring==23.13.1
lockfile==0.12.2
more-itertools==9.0.0
msgpack==1.0.4
packaging==23.0
pexpect==4.8.0
pkginfo==1.9.6
platformdirs==2.6.2
poetry==1.3.2
poetry-core==1.4.0
poetry-plugin-export==1.2.0
ptyprocess==0.7.0
pyrsistent==0.19.3
pywin32-ctypes==0.2.0
rapidfuzz==2.13.7
requests==2.28.2
requests-toolbelt==0.10.1
shellingham==1.5.0.post1
six==1.16.0
tomli==2.0.1
tomlkit==0.11.6
trove-classifiers==2023.1.12
urllib3==1.26.14
virtualenv==20.16.5
webencodings==0.5.1
zipp==3.11.0

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[hukkin]

Thanks, and sorry for taking so long to respond. #409 fixes this and a couple other issues.

[guykisel]

oh, thank you! <3