pathlib.Path.glob causes OSError encountering symlinks to long filenames

[ericfrederich]

BPO	43529
Nosy	@ericfrederich
Files	uhoh.py: Reproduces bug

^{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 2021-03-17.15:23:36.025>
labels = ['3.7', '3.8', '3.9', '3.10']
title = 'pathlib.Path.glob causes OSError encountering symlinks to long filenames'
updated_at = <Date 2021-03-19.11:28:12.066>
user = 'https://github.com/ericfrederich'

bugs.python.org fields:

activity = <Date 2021-03-19.11:28:12.066>
actor = 'eric.frederich'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2021-03-17.15:23:36.025>
creator = 'eric.frederich'
dependencies = []
files = ['49884']
hgrepos = []
issue_num = 43529
keywords = []
message_count = 3.0
messages = ['388927', '388928', '389073']
nosy_count = 1.0
nosy_names = ['eric.frederich']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue43529'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10']

Linked PRs

• GH-87695: Fix OSError from pathlib.Path.glob() #104292
• [3.11] GH-87695: Fix OSError from pathlib.Path.glob() (GH-104292) #104362

[ericfrederich]

Calling pathlib.Path.glob("**/*) on a directory containing a symlink which resolves to a very long filename causes OSError.

This is completely avoidable since symlinks are not followed anyway.

In pathlib.py, the _RecursiveWildcardSelector has a method _iterate_directories which first calls entry.is_dir() prior to excluding based on entry.is_symlink().

It's the entry.is_dir() which is failing.
If the check for entry.is_symlink() were to happen first this error would be avoided.

It's worth noting that on Linux "ls -l bad_link" works fine.
Also "find /some/path/containing/bad/link" works fine.
You do get an error however when running "ls bad_link"
I believe Python's glob() should act like "find" on Linux and not fail.
Because it is explicitly ignoring symlinks anyway, it has no business calling is_dir() on a symlink.

I have attached a file which reproduces this problem. It's meant to be ran inside of an empty directory.

[ericfrederich]

I verified against all versions available for me to select.
For 3.10 I used the 3.10-rc Docker image.

[ericfrederich]

I'm happy to create a pull request but would need some help.

Looking at that routine it has changed over time and I cannot simply create a single patch against 3.6 and have it merge cleanly into newer versions.

I'd need help explaining the process

[barneygale]

Fixed in 3.12: #104292 / a33ce66

Backported to 3.11: #104362 / 846a23d

[encukou]

Note that this is "fixed" (the error is ignored) in 3.8+ in #79487