Re: shutil.rmtree() fails when used in Fedora (rpm) "mock" environment

On 2024-10-24 16:17, Left Right via Python-list wrote:

 From reading the code where the exception is coming from, this is how
I interpret the intention of the author: they build a list (not sure
why they used list, when there's a stack datastructure in Python)
which they use as a stack, where the elements of the stack are
4-tuples, the important part about these tuples is that the first
element is the operation to be performed by rmtree() has to be one of
the known filesystem-related functions. The code raising the exception
checks that it's one of those kinds and if it isn't, crashes.
 There is, however, a problem with testing equality (more strictly,
identity in this case) between functions.  I.e. it's possible that a
function isn't identical to itself is, eg. "os" module was somehow
loaded twice.  I'm not sure if that's a real possibility with how
Python works... but maybe in some cases, like, multithreaded
environments it could happen...
 To investigate this, I'd edit the file with the assertion and make it
print the actual value found in os.lstat and func.  My guess is that
they are both somehow "lstat", but with different memory addresses.
 

The stack is created on line 760 with os.lstat and entries are appended on lines 677 (os.rmdir), 679 (os.close) and 689 (os.lstat).
'func' is popped off the stack on line 651 and check in the following lines.
I can't see anywhere else where something else is put onto the stack or an entry is replaced.

On Thu, Oct 24, 2024 at 4:06 PM Christian Buhtz via Python-list
<python-list@python.org> wrote:

>
Hello,
I am upstream maintainer of "Back In Time" [1] investigating an issue a
distro maintainer from Fedora reported [2] to me.
>
On one hand Fedora seems to use a tool called "mock" to build packages
in a chroot environment.
On the other hand the test suite of "Back In Time" does read and write
to the real file system.
One test fails because a temporary directory is cleaned up using
shutil.rmtree(). Please see the output below.
>
I am not familiar with Fedora and "mock". So I am not able to reproduce
this on my own.
It seems the Fedora maintainer also has no clue how to solve it or why
it happens.
>
Can you please have a look (especially at the line "assert func is
os.lstat").
Maybe you have an idea what is the intention behind this error raised by
an "assert" statement inside "shutil.rmtree()".
>
Thanks in advance,
Christian Buhtz
>
[1] -- <https://github.com/bit-team/backintime>
[2] -- <https://github.com/bit-team/backintime/issues/1911>
>
__________________________ General.test_ctor_defaults
__________________________
self = <test.test_uniquenessset.General testMethod=test_ctor_defaults>
     def test_ctor_defaults(self):
         """Default values in constructor."""

      with TemporaryDirectory(prefix='bit.') as temp_name:

test/test_uniquenessset.py:47:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _
/usr/lib64/python3.13/tempfile.py:946: in __exit__
     self.cleanup()
/usr/lib64/python3.13/tempfile.py:950: in cleanup
     self._rmtree(self.name, ignore_errors=self._ignore_cleanup_errors)
/usr/lib64/python3.13/tempfile.py:930: in _rmtree
     _shutil.rmtree(name, onexc=onexc)
/usr/lib64/python3.13/shutil.py:763: in rmtree
     _rmtree_safe_fd(stack, onexc)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _
stack = []
onexc = <function TemporaryDirectory._rmtree.<locals>.onexc at
0xffffb39bc860>
     def _rmtree_safe_fd(stack, onexc):
         # Each stack item has four elements:
         # * func: The first operation to perform: os.lstat, os.close or
os.rmdir.
         #   Walking a directory starts with an os.lstat() to detect
symlinks; in
         #   this case, func is updated before subsequent operations and
passed to
         #   onexc() if an error occurs.
         # * dirfd: Open file descriptor, or None if we're processing the
top-level
         #   directory given to rmtree() and the user didn't supply
dir_fd.
         # * path: Path of file to operate upon. This is passed to
onexc() if an
         #   error occurs.
         # * orig_entry: os.DirEntry, or None if we're processing the
top-level
         #   directory given to rmtree(). We used the cached stat() of
the entry to
         #   save a call to os.lstat() when walking subdirectories.
         func, dirfd, path, orig_entry = stack.pop()
         name = path if orig_entry is None else orig_entry.name
         try:
             if func is os.close:
                 os.close(dirfd)
                 return
             if func is os.rmdir:
                 os.rmdir(name, dir_fd=dirfd)
                 return
>
             # Note: To guard against symlink races, we use the standard
             # lstat()/open()/fstat() trick.

          assert func is os.lstat

E           AssertionError
/usr/lib64/python3.13/shutil.py:663: AssertionError
>
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