TypeError: unhashable type: 'list' when using dulwich 0.24.6 with Python <3.9.2

Hi!

This may end up being wontfix (given it only affects older Python 3.9 patch versions), but filing for awareness / in case it helps others.

With the release of dulwich 0.24.6 our CI started failing with TypeError: unhashable type: 'list' errors when invoking Poetry with Python 3.9.0.

For example:
https://github.com/heroku/heroku-buildpack-python/actions/runs/18650476440/job/53167114670?pr=1941#step:5:544

I was able to reproduce this outside of Poetry - it affects Python 3.9.0 and 3.9.1 only (and not Python 3.9.2+).

For example:

$ docker run --rm python:3.9.1-slim bash -c 'pip install --disable-pip-version-check dulwich==0.24.6 && python -c "from dulwich import porcelain"'
Collecting dulwich==0.24.6
  Downloading dulwich-0.24.6-cp39-cp39-manylinux_2_28_aarch64.whl (1.3 MB)
Collecting urllib3>=2.2.2
  Downloading urllib3-2.5.0-py3-none-any.whl (129 kB)
Collecting typing_extensions>=4.0
  Downloading typing_extensions-4.15.0-py3-none-any.whl (44 kB)
Installing collected packages: urllib3, typing-extensions, dulwich
Successfully installed dulwich-0.24.6 typing-extensions-4.15.0 urllib3-2.5.0
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/dulwich/porcelain.py", line 126, in <module>
    from .bisect import BisectState
  File "/usr/local/lib/python3.9/site-packages/dulwich/bisect.py", line 29, in <module>
    from dulwich.repo import Repo
  File "/usr/local/lib/python3.9/site-packages/dulwich/repo.py", line 66, in <module>
    from . import reflog, replace_me
  File "/usr/local/lib/python3.9/site-packages/dulwich/reflog.py", line 208, in <module>
    reachable_checker: Optional[Callable[[bytes], bool]] = None,
  File "/usr/local/lib/python3.9/typing.py", line 262, in inner
    return func(*args, **kwds)
  File "/usr/local/lib/python3.9/typing.py", line 339, in __getitem__
    return self._getitem(self, parameters)
  File "/usr/local/lib/python3.9/typing.py", line 463, in Optional
    return Union[arg, type(None)]
  File "/usr/local/lib/python3.9/typing.py", line 262, in inner
    return func(*args, **kwds)
  File "/usr/local/lib/python3.9/typing.py", line 339, in __getitem__
    return self._getitem(self, parameters)
  File "/usr/local/lib/python3.9/typing.py", line 451, in Union
    parameters = _remove_dups_flatten(parameters)
  File "/usr/local/lib/python3.9/typing.py", line 231, in _remove_dups_flatten
    return tuple(_deduplicate(params))
  File "/usr/local/lib/python3.9/typing.py", line 205, in _deduplicate
    all_params = set(params)
TypeError: unhashable type: 'list'

To resolve the error, one needs to either:

Downgrade dulwich to 0.24.5 or older
Or, upgrade Python 3.9.0/3.9.1 to Python 3.9.2 or newer

The typing usage that is tripping up the typing module is on this line:

dulwich/dulwich/reflog.py

Line 208 in 1702e77

reachable_checker: Optional[Callable[[bytes], bool]] = None,

And was introduced in this PR:
https://github.com/jelmer/dulwich/pull/1941/files#diff-d4672769f4e2861358cbfa19fdf0f71c481575deec25d702a93f96baecf5cf6cR208

Looking at the Python 3.9.2 release notes:
https://docs.python.org/3.9/whatsnew/changelog.html#python-3-9-2-final

...I see this entry:

bpo-42195: The args of the parameterized generics for typing.Callable and collections.abc.Callable are now consistent. The args for collections.abc.Callable are now flattened while typing.Callable’s have not changed. To allow this change, types.GenericAlias can now be subclassed and collections.abc.Callable’s class_getitem will now return a subclass of types.GenericAlias. Tests for typing were also updated to not subclass things like Callable[..., T] as that is not a valid base class. Finally, both types no longer validate their argtypes, in Callable[[argtypes], resulttype] to prepare for PEP 612. Patch by Ken Jin.

It seems like the relevant upstream CPython 3.9 change that resolves this issue, is that in the last sentence? ("both types no longer validate their argtypes") ie:

Additional context

The reason we have a test for Python 3.9.0, is that our tool (a buildpack) allows end users to pick arbitrary Python versions to install (similar to pyenv or GitHub Actions allowing people to pick their Python version) - and so to ensure backwards compatibility, we not only have tests for each supported Python package manager against the latest patch release of each major Python version (3.9-3.14), but also the oldest available Python version too (ie for Python 3.9 we test both 3.9.24 and 3.9.0). We're due to drop end-user support for Python 3.9 in January 2026.

So one possible workaround on the dulwich side, might be to:

Adjust requires_python to be >=3.9.2 rather than >=3.9 (

dulwich/pyproject.toml

Line 26 in 1702e77

requires-python = ">=3.9"

)
Publish dulwich 0.24.7 with that change
Then mark dulwich 0.24.6 as yanked on PyPI

Doing this would mean a pip install dulwich on Python 3.9.0 / 3.9.1 would cause pip to automatically backtrack the dulwich package version back down to 0.24.5, without the need for end users knowing they need to explicitly specify dulwich<0.24.6. (Yanking doesn't delete the old version - anyone who pins explicitly to dulwich==0.24.6 will still be able to use it.)

Would this be something you'd be open to? :-)

Pin Poetry's `dulwich` version

Pin Poetry's `dulwich` version (#1943)

Pin Poetry's `dulwich` version (#447)

Work around typing module bug in Python 3.9.0/3.9.1

I'm inclined to just convert this type annotation to a string one for now, that should probably address it.

@edmorley

@edmorley any chance you could test #1949 with python 3.9.0? I don't have easy access to Python 3.9.0 anymore unfortunately.

Work around typing module bug in Python 3.9.0/3.9.1

Thank you for the quick reply!

#1949 fixes the error for me, when testing locally using Docker (and the non-slim Python image, which contains Git) and dulwich installed from the PR's branch :-)

$ docker run --rm python:3.9.0 bash -c 'pip install --disable-pip-version-check "dulwich @ git+https://github.com/jelmer/dulwich@typing-workaround" && python -c "from dulwich import porcelain"'
Collecting dulwich@ git+https://github.com/jelmer/dulwich@typing-workaround
  Cloning https://github.com/jelmer/dulwich (to revision typing-workaround) to /tmp/pip-install-f5gfqs91/dulwich_70e9ff1ce4c5412fab3499788ede33ab
  Installing build dependencies: started
  Installing build dependencies: finished with status 'done'
  Getting requirements to build wheel: started
  Getting requirements to build wheel: finished with status 'done'
  Installing backend dependencies: started
  Installing backend dependencies: finished with status 'done'
    Preparing wheel metadata: started
    Preparing wheel metadata: finished with status 'done'
Collecting typing_extensions>=4.0
  Downloading typing_extensions-4.15.0-py3-none-any.whl (44 kB)
Collecting urllib3>=2.2.2
  Downloading urllib3-2.5.0-py3-none-any.whl (129 kB)
Building wheels for collected packages: dulwich
  Building wheel for dulwich (PEP 517): started
  Building wheel for dulwich (PEP 517): finished with status 'done'
  Created wheel for dulwich: filename=dulwich-0.24.7-cp39-cp39-linux_aarch64.whl size=538322 sha256=b06834ea956ff0ee29b18644a08caa354b2a3b38ff7a920da696339b5cf3ec37
  Stored in directory: /tmp/pip-ephem-wheel-cache-sl453ral/wheels/31/60/55/23be01292f4c0d233736bfa46a377c018eae2883cf15bf3f6a
Successfully built dulwich
Installing collected packages: urllib3, typing-extensions, dulwich
Successfully installed dulwich-0.24.7 typing-extensions-4.15.0 urllib3-2.5.0

Great, thanks for verifying!

Work around typing module bug in Python 3.9.0/3.9.1 (#1949)

Work around typing module bug in Python 3.9.0/3.9.1

Work around typing module bug in Python 3.9.0/3.9.1 (#1949)

Unpin Poetry's `dulwich` version

Unpin Poetry's `dulwich` version (#464)

Unpin Poetry's `dulwich` version

Unpin Poetry's `dulwich` version (#1967)

Work around typing module bug in Python 3.9.0/3.9.1

Work around typing module bug in Python 3.9.0/3.9.1 (#1949)

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`TypeError: unhashable type: 'list'` when using dulwich 0.24.6 with Python <3.9.2 #1948

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TypeError: unhashable type: 'list' when using dulwich 0.24.6 with Python <3.9.2 #1948

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edmorley commented on Oct 21, 2025

jelmer commented on Oct 21, 2025

jelmer commented on Oct 21, 2025

edmorley commented on Oct 21, 2025

jelmer commented on Oct 21, 2025

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`TypeError: unhashable type: 'list'` when using dulwich 0.24.6 with Python <3.9.2 #1948