Broken symlink fails `os.path.exists(symlink)` check but raises FileExists error in `os.makedirs(symlink, exist_ok=True)`.

[LeoZDong]

Bug report

Bug description:

Description

Suppose I have a symlink that points to original, and then original gets deleted, which makes it an invalid symlink. I get an unexpected behavior where:

os.path.exists("symlink")
>>> False
os.makedirs("symlink", exist_ok=True)
>>> FileExistsError: [Errno 17] File exists: "symlink"

Why this is important

It is not uncommon for code to rely on os.makedirs(..., exist_ok=True) to create a directory only if it exists, or to use a if not os.path.exists(...) to guard before calling os.makedirs(...). In the case when the given directory is a broken symlink, this would no longer work. In particular, raising a FileExistsError when exist_ok=True is especially confusing, and this behavior should be avoided.

Steps to reproduce

In terminal, create a broken symlink

mkdir original
ln -s original symlink
rm -r original

In Python, observe:

os.path.exists("symlink")
>>> False
os.makedirs("symlink", exist_ok=True)
>>> FileExistsError: [Errno 17] File exists: "symlink"

Python version: 3.12.8

Expected behavior

os.path.exists behavior should be consistent with os.makedirs. When given a broken symlink, either:

1. os.path.exists(symlink) returns True (does not implicitly resolve symlink) and os.makedirs(symlink, exist_ok=True) does nothing
2. OR: os.path.exists(symlink) returns False (implicitly resolves symlink) and os.makedirs(symlink, exist_ok=True) creates a directory at the symlink target.

1 might be the preferred behavior since implicitly resolving symlink is kind of bad. Open to other options (perhaps a special error for handling symlinks), but regardless the main thing is to fix the behavior where a FileExistsError is raised even when exist_ok=True is passed.

CPython versions tested on:

3.12

Operating systems tested on:

Linux

[picnixz]

What happens when you do mkdir -p symlink? does it also fail? if so, it's better to align with POSIX. If not, let's align with POSIX

[picnixz]

I can confirm that it's what POSIX does, namely we do have an error and mkdir -p symlink reports that the file already exists.

I can also confirm that test -e symlink && echo 1 prints nothing so a broken symlink is not considered to be existing. Considering this, I will close this one as wont fix as we would diverge from POSIX otherwise.

[LeoZDong]

@picnixz Thanks! If mkdir -p symlink reports that the file already exists, should os.makedirs("symlink", exist_ok=True) just do nothing instead of raising a FileExistsError? I'm mainly concerned with getting a FileExistsError when I explicitly give it exist_ok=True.

[picnixz]

Well... technically speaking, makedirs was meant to behave like mkdir -p and the latter shouldn't err if the file already exists but it does. I guess it's because it's a symlink (and this might be treated differently than a regular file).

@barneygale @serhiy-storchaka Maybe we could document that the exception can still be raised in case of symlinks? or we can indeed suppress that exception internally (though it would then diverge from POSIX...)

[serhiy-storchaka]

It does not check that the file exists. It checks that the directory exists. You can test it with an existing file (not directory).

This is expected behavior. This is not success, because the path is not an existing directory. The directory with that path cannot be created, because other entry already exists. So this is an error.