👽️ Ensure compatibility with Pydantic 2.12.0 #14036

cjwatson · 2025-09-02T11:58:36Z

tests/test_multi_body_errors.py::test_openapi_schema failed with pydantic 2.12.0a1 due to
pydantic/pydantic#11987. Since we're testing the exact contents of the JSON schema, the easiest fix seems to be to add version-dependent handling for this.

YuriiMotov · 2025-09-02T17:39:50Z

I think we should try to avoid adding new dependency.

Maybe something with dirty_equals?
Take a look at the code in the details

Details

from dirty_equals import IsOneOf

v1 = {
    "age": {
        "title": "Age",
        "anyOf": [
            {"exclusiveMinimum": 0.0, "type": "number"},
            {"type": "string"},
        ],
    }
}

v2 = {
    "age": {
        "title": "Age",
        "anyOf": [
            {"exclusiveMinimum": 0.0, "type": "number"},
            {"type": "string", "pattern": r"^(?!^[-+.]*$)[+-]?0*\d*\.?\d*$"},
        ],
    }
}


expected = {
    "age": {
        "title": "Age",
        "anyOf": [
            {"exclusiveMinimum": 0.0, "type": "number"},
            IsOneOf(
                {"type": "string"},
                {"type": "string", "pattern": r"^(?!^[-+.]*$)[+-]?0*\d*\.?\d*$"}
            ),
        ],
    }
}

assert v1 == expected
assert v2 == expected

cjwatson · 2025-09-07T17:09:10Z

I think we should try to avoid adding new dependency.

Maybe something with dirty_equals? Take a look at the code in the details

Ah yes, that works too, thanks. Amended.

YuriiMotov · 2025-09-09T14:29:25Z

I just tried running this branch with pydantic 2.12.0a1, and I have 4 failed tests

FAILED tests/test_forms_single_model.py::test_send_all_data - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...
FAILED tests/test_forms_single_model.py::test_defaults - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...
FAILED tests/test_forms_single_model.py::test_invalid_data - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...
FAILED tests/test_forms_single_model.py::test_no_data - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...

cjwatson · 2025-09-18T08:25:30Z

I just tried running this branch with pydantic 2.12.0a1, and I have 4 failed tests

FAILED tests/test_forms_single_model.py::test_send_all_data - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...
FAILED tests/test_forms_single_model.py::test_defaults - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...
FAILED tests/test_forms_single_model.py::test_invalid_data - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...
FAILED tests/test_forms_single_model.py::test_no_data - pydantic.warnings.UnsupportedFieldAttributeWarning: The 'alias' attribute with value 'with' was provided to the `Field()` function, which has no effect in the context it was used. 'alias' is field-spec...

These are due to pydantic/pydantic#12028. In that PR, @Viicos wrote:

I've reached out to the FastAPI team regarding the failing tests. They will need to address them in some way.

But I really don't follow what FastAPI is doing here; it seems to be something to do with ModelField.__post_init__ in fastapi/_compat.py? Somebody who's actually an expert in that code would need to weigh in, I think. Maybe @tiangolo?

Viicos · 2025-09-21T14:53:46Z

I discussed internally with the FastAPI team a while ago about this. The fix I proposed was to use the warning.catch_warnings context manager when creating type adapters in FastAPI. Pydantic emits a specific UnsupportedFieldAttributeWarning in this case, so it can safely be filtered while still having other potential warnings raised.

cjwatson · 2025-09-21T19:21:17Z

The fix I proposed is to use warning.catch_warnings context manager when creating type adapters in FastAPI.

OK, thanks for the advice. a33cc0a implements that.

fastapi/_compat.py

tests/test_multi_body_errors.py

* run test suite on Python 3.14 * add 3.14 classifier * allow Python pre-release for now * exclude pydantic v1 on Python 3.14 * install pydantic 1.12.0 alpha1 when testing on python 3.14 * preinstall pydantic 1.12.0 alpha1 before anything else

svlandeg · 2025-09-24T16:02:44Z

I changed the base branch of this PR to feature/py314 where we've got a CI run for Python 3.14 and Pydantic 2.12 set up - this way we can actually see the failing tests 😉

cjwatson · 2025-09-25T11:48:13Z

@svlandeg That seems to have resulted in a pile of errors that have nothing to do with this branch. Or am I missing something?

`tests/test_multi_body_errors.py::test_openapi_schema` failed with pydantic 2.12.0a1 due to pydantic/pydantic#11987. Since we're testing the exact contents of the JSON schema, the easiest fix seems to be to add version-dependent handling for this.

@Viicos

Recommended by @Viicos from the Pydantic team.

Co-authored-by: Victorien <65306057+Viicos@users.noreply.github.com>

svlandeg · 2025-09-25T17:56:54Z

@svlandeg That seems to have resulted in a pile of errors that have nothing to do with this branch. Or am I missing something?

I think these are exactly the errors that need resolving - the test suite now actually runs Pydantic 2.12.0a1 on Python 3.14 (rc)?

(they're really all mostly versions of the same error, from a quick glance)

svlandeg · 2025-09-25T17:59:16Z

PS: @cjwatson: it's fine if you don't want to continue working on those other errors - just let us know - and we'll take over this branch because they need fixing anyway 😉

cjwatson · 2025-09-26T09:35:46Z

Those errors don't appear to happen in my local setup with pydantic 2.12.0a1 on Python 3.13 (which was what I was originally trying to fix with this PR). I'd appreciate it if somebody else could take over the rest of those fixes, yes.

svlandeg · 2025-09-26T11:11:56Z

Those errors don't appear to happen in my local setup with pydantic 2.12.0a1 on Python 3.13 (which was what I was originally trying to fix with this PR)

I think you're right - those additional errors are new in Python 3.14.

I'd appreciate it if somebody else could take over the rest of those fixes, yes.

Sure thing - I'm going to look into them now. I'll probably merge this PR into our feature branch feature/py314 and continue from there.

svlandeg

Ok, just to recap and apologies for the earlier confusion!

This PR ensures compatibility with Pydantic 2.12.0, which will be released soon.

In particular, pydantic 2.12.0a1 causes 2 types of failures in our test suite:

test_openapi_schema fails due to pydantic/pydantic#11987 as explained by OP. The test is adjusted to work on both new and older versions of Pydantic.
warnings about using the alias attribute with value with in the Field() function, cf PR pydantic/pydantic#12028. This PR suppresses those warnings when creating type adapters in FastAPI, which seems like a reasonable solution to me.

I had intended to merge these fixes as part of a larger PR to get ready for Python 3.14, but have reverted that and suggest we merge & release this separately to ensure compatibility with the upcoming Pydantic 2.12.0.

Thanks again for your work on this, @cjwatson !

Outdated

fastapi/_compat.py

tiangolo

Nice, thank you @cjwatson! 🚀

And thanks a lot for all the help here @YuriiMotov, @Viicos, @svlandeg, @patrick91 🙌

So cool to come and see all the conversations already done, the code simplified to the minimum, all the context easy to get quickly. Great job, thank you all! 🍰

I'll release this in the next hours/minutes in FastAPI 0.118.1 🎉

github-actions bot added the internal label Sep 2, 2025

cjwatson force-pushed the pydantic-2.12.0a1 branch from d7ada00 to a9d228a Compare September 2, 2025 16:18

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cjwatson force-pushed the pydantic-2.12.0a1 branch from a9d228a to dbe54cb Compare September 7, 2025 17:08

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SaisakthiM mentioned this pull request Sep 10, 2025

👽️ Update Color import depending on the version of Pydantic #14060

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cjwatson force-pushed the pydantic-2.12.0a1 branch 5 times, most recently from dc01ba4 to a33cc0a Compare September 22, 2025 09:58

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svlandeg mentioned this pull request Sep 24, 2025

⬆️ Add support for Python 3.14 #14110

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svlandeg changed the base branch from master to feature/py314 September 24, 2025 15:58

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cjwatson force-pushed the pydantic-2.12.0a1 branch from 1869b53 to cdd831e Compare September 25, 2025 11:52

cjwatson and others added 4 commits September 25, 2025 12:55

Prepare for pydantic 2.12.0

5386c5d

`tests/test_multi_body_errors.py::test_openapi_schema` failed with pydantic 2.12.0a1 due to pydantic/pydantic#11987. Since we're testing the exact contents of the JSON schema, the easiest fix seems to be to add version-dependent handling for this.

Ignore UnsupportedFieldAttributeWarning when creating type adapters

716ecee

Recommended by @Viicos from the Pydantic team.

Apply suggestions from code review

42ae353

Co-authored-by: Victorien <65306057+Viicos@users.noreply.github.com>

Use explicit pydantic version check

2ba181e

cjwatson force-pushed the pydantic-2.12.0a1 branch from cdd831e to 2ba181e Compare September 25, 2025 11:56

cjwatson marked this pull request as ready for review September 25, 2025 11:57

svlandeg marked this pull request as draft September 25, 2025 17:58

svlandeg marked this pull request as ready for review September 26, 2025 11:27

svlandeg changed the base branch from feature/py314 to master October 7, 2025 09:43

svlandeg added 2 commits October 7, 2025 11:46

remove py3.14 stuff again

5383450

Merge branch 'master' into pydantic-2.12.0a1

79a2566

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⬆️ Add support for Python 3.14 #14165

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Merge branch 'master' into pydantic-2.12.0a1

fb40165

Remove no cover now that Pydantic 2.12 is out

13f6949

Remove unused type ignore

973b657

Ignore Cannot inherit from final class "FieldInfo"

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tiangolo merged commit c970d8a into fastapi:master Oct 8, 2025
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👽️ Ensure compatibility with Pydantic 2.12.0 #14036

👽️ Ensure compatibility with Pydantic 2.12.0 #14036

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