Python 3.14 incompatibility related to some typing objects being immutable

[freakboy3742]

I've been starting some pre-release testing with Python 3.14.0a6, and httpcore appears to have an incompatibility, preventing httpcore from being imported:

(venv3.14) rkm@eunectes temp % pip install httpcore
Collecting httpcore
  Using cached httpcore-1.0.7-py3-none-any.whl.metadata (21 kB)
...
Successfully installed certifi-2025.1.31 h11-0.14.0 httpcore-1.0.7
(venv3.14) rkm@eunectes temp % python
Python 3.14.0a6 (v3.14.0a6:77b2c933cab, Mar 14 2025, 11:45:56) [Clang 16.0.0 (clang-1600.0.26.6)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
im>>> import httpcore
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    import httpcore
  File "/Users/rkm/temp/venv3.14/lib/python3.14/site-packages/httpcore/__init__.py", line 140, in <module>
    setattr(__locals[__name], "__module__", "httpcore")  # noqa
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'typing.Union' object has no attribute '__module__' and no __dict__ for setting new attributes. Did you mean: '__reduce__'?
>>> 

Catching the AttributeError fixes the problem in my (limited) testing:

__locals = locals()
for __name in __all__:
    if not __name.startswith("__"):
        try:
            setattr(__locals[__name], "__module__", "httpcore")  # noqa
        except AttributeError:
            pass

If I make this modification manually, the import succeeds; and my usage of httpcore (by way of briefcase invoking httpx) succeeds.

The underlying issue is that in 3.14, the Union type has a binary implementation, so it no longer has a __module__ attribute. Catching the AttributeError means that any other object that is moved into a binary module won't trigger the same problem.

[zanieb]

This makes sense to me, but we should probably understand why that code exists in the first place.

It was last touched in #420 but existed previously and was introduced in b0cfafd (issue #148) with the original motivation in encode/httpx#1155.

So... seems fine to skip this where it's not applicable. I wonder how the repr changes since that was the original goal?

[tomchristie]

The underlying issue is that in 3.14, the Union type has a binary implementation

"What's the value of __name at that point?"

Ah okay, presumably SOCKET_OPTION. (?) ^*

I wonder how the repr changes since that was the original goal?

Good question. It's the difference between an instance without a built-in repr displaying as (eg) <httpx._client.Client> and <httpx.Client> on the console.

The cleanest resolution here might be to ensure that all the classes referenced in __name__ do have an defined __repr__, rather than using monkey patching at import.

^* backtracking through that particular case being public API points to an earlier poor API decision. Although I don't want to side-track the discussion too much here.

[freakboy3742]

Confirming that yes - it's SOCKET_OPTION that is the problem symbol.

[tomchristie]

Confirming that yes - it's SOCKET_OPTION that is the problem symbol.

Thanks Russ. The cheap fix here would be to have an exclusion for that case in the if not name.startswith(...) clause.

One liner PR if anyone's motivated to resolve it.

[hugovk]

Please see PR #1005.

[hugovk]

This is now released in httpcore 1.0.8.

Thanks everyone!

[vytas7]

(Just adding from the now deleted #994, this issue is new in 3.14.0a6; 3.14.0a5 does not exhibit the same problem.)

[zanieb]

I spent so long looking for that... I knew I'd seen it before

[hugovk]

Bisecting CPython between a5 and a6, the change is python/cpython#105511: "Merge typing.Union and types.UnionType".

[klmcwhirter]

Do you guys have a plan for this to be included in an upcoming release? If so, any ETA?

If not, are there other things being considered?

My vote would be to not modify code not belonging to this project at runtime. What other things might break because of this bit of meta-programming?

BTW - I applied the patch mentioned above locally and that is what I needed to be able to install PDM with python3.14.0a6 .

Thanks.

[codebydivine]

You can use this monkey patch I did meanwhile it's fixed: encode/httpx#3548 (comment)

[illia-v]

urllib3 uses httpcore for proxy tests, and tests with Python 3.14 fail because of this issue urllib3/urllib3#3576, we have a $100 bounty for fixing our CI

[codebydivine]

bounty

You can use this monkey patch to fix the issue meanwhile: encode/httpx#3548 (comment)