Fix annotations support on 3.14 by JelleZijlstra · Pull Request #852 · jcrist/msgspec

JelleZijlstra · 2025-05-26T16:09:36Z

With this change, the tests run for me on a local build of Python 3.14.
There are a lot of failures related to sys.getrefcount() but that seems
to be an unrelated issue.

Closes #810. Fixes #651. Fixes #795.

With this change, the tests run for me on a local build of Python 3.14. There are a lot of failures related to sys.getrefcount() but that seems to be an unrelated issue. Closes jcrist#810. Fixes jcrist#651. Fixes jcrist#795.

JelleZijlstra · 2025-05-26T16:12:21Z

+    if (annotations == NULL) {
+        if (mod->get_annotate_from_class_namespace != NULL) {
+            PyObject *annotate = PyObject_CallOneArg(
+                mod->get_annotate_from_class_namespace, info->namespace


This is the portable approach, which should continue to work on future Python versions. If you value performance over portability, you can instead inline this function https://github.com/python/cpython/blob/9ddc7c548d45b73c84131e6d75b03c26a3e8b6e8/Lib/annotationlib.py#L824 ; it's just dict operations.

I made it a separate function in CPython so that we can be free to optimize the internal representation of annotate functions in the future. For example, perhaps in 3.15 the class will store just a code object instead of a function.

JelleZijlstra · 2025-05-26T16:13:34Z

            value = _eval_type(value, cls_locals, cls_globals)
            if mapping is not None:
                value = _apply_params(value, mapping)
+            if value is None:


I changed _eval_type so it no longer turns None into NoneType.

hroncok · 2025-05-26T16:50:54Z

I get a copule of SystemError: error return without exception set:

___________ TestTypedDict.test_total_partially_optional[json-False] ____________

self = <test_common.TestTypedDict object at 0x7f25e7f160a0>
proto = <module 'msgspec.json' from '/builddir/build/BUILD/python-msgspec-0.19.0-build/BUILDROOT/usr/lib64/python3.14/site-packages/msgspec/json.py'>
use_typing_extensions = False

    @pytest.mark.parametrize("use_typing_extensions", [False, True])
    def test_total_partially_optional(self, proto, use_typing_extensions):
        if use_typing_extensions:
            tex = pytest.importorskip("typing_extensions")
            cls = tex.TypedDict
        else:
            cls = TypedDict
    
        class Base(cls):
            a: int
            b: str
    
        class Ex(Base, total=False):
            c: str
    
        dec = proto.Decoder(Ex)
    
        x = {"a": 1, "b": "two", "c": "extra"}
>       assert dec.decode(proto.encode(x)) == x
E       SystemError: <built-in method decode of msgspec.json.Decoder object at 0x7f25e89b85e0> returned NULL without setting an exception

tests/test_common.py:2106: SystemError
__________ TestTypedDict.test_total_partially_optional[msgpack-False] __________

self = <test_common.TestTypedDict object at 0x7f25e7fcab70>
proto = <module 'msgspec.msgpack' from '/builddir/build/BUILD/python-msgspec-0.19.0-build/BUILDROOT/usr/lib64/python3.14/site-packages/msgspec/msgpack.py'>
use_typing_extensions = False

    @pytest.mark.parametrize("use_typing_extensions", [False, True])
    def test_total_partially_optional(self, proto, use_typing_extensions):
        if use_typing_extensions:
            tex = pytest.importorskip("typing_extensions")
            cls = tex.TypedDict
        else:
            cls = TypedDict
    
        class Base(cls):
            a: int
            b: str
    
        class Ex(Base, total=False):
            c: str
    
        dec = proto.Decoder(Ex)
    
        x = {"a": 1, "b": "two", "c": "extra"}
>       assert dec.decode(proto.encode(x)) == x
E       SystemError: error return without exception set

tests/test_common.py:2106: SystemError
___________ TestTypedDict.test_required_and_notrequired[json-False] ____________

self = <test_common.TestTypedDict object at 0x7f25e813e180>
proto = <module 'msgspec.json' from '/builddir/build/BUILD/python-msgspec-0.19.0-build/BUILDROOT/usr/lib64/python3.14/site-packages/msgspec/json.py'>
use_typing_extensions = False

    @pytest.mark.parametrize("use_typing_extensions", [False, True])
    def test_required_and_notrequired(self, proto, use_typing_extensions):
        if use_typing_extensions:
            module = "typing_extensions"
        else:
            module = "typing"
    
        ns = pytest.importorskip(module)
    
        if not hasattr(ns, "Required"):
            pytest.skip(f"{module}.Required is not available")
    
        source = f"""
        from __future__ import annotations
        from {module} import TypedDict, Required, NotRequired
    
        class Base(TypedDict):
            a: int
            b: NotRequired[str]
    
        class Ex(Base, total=False):
            c: str
            d: Required[bool]
        """
    
        with temp_module(source) as mod:
            dec = proto.Decoder(mod.Ex)
    
            x = {"a": 1, "b": "two", "c": "extra", "d": False}
>           assert dec.decode(proto.encode(x)) == x
E           SystemError: <built-in method decode of msgspec.json.Decoder object at 0x7f25e91a0590> returned NULL without setting an exception

tests/test_common.py:2144: SystemError
__________ TestTypedDict.test_required_and_notrequired[msgpack-False] __________

self = <test_common.TestTypedDict object at 0x7f25e8199550>
proto = <module 'msgspec.msgpack' from '/builddir/build/BUILD/python-msgspec-0.19.0-build/BUILDROOT/usr/lib64/python3.14/site-packages/msgspec/msgpack.py'>
use_typing_extensions = False

    @pytest.mark.parametrize("use_typing_extensions", [False, True])
    def test_required_and_notrequired(self, proto, use_typing_extensions):
        if use_typing_extensions:
            module = "typing_extensions"
        else:
            module = "typing"
    
        ns = pytest.importorskip(module)
    
        if not hasattr(ns, "Required"):
            pytest.skip(f"{module}.Required is not available")
    
        source = f"""
        from __future__ import annotations
        from {module} import TypedDict, Required, NotRequired
    
        class Base(TypedDict):
            a: int
            b: NotRequired[str]
    
        class Ex(Base, total=False):
            c: str
            d: Required[bool]
        """
    
        with temp_module(source) as mod:
            dec = proto.Decoder(mod.Ex)
    
            x = {"a": 1, "b": "two", "c": "extra", "d": False}
>           assert dec.decode(proto.encode(x)) == x
E           SystemError: error return without exception set

tests/test_common.py:2144: SystemError

Do you also get those?

JelleZijlstra · 2025-05-26T16:55:21Z

I didn't how, are you running the test suite exactly?

I get these failures which all seem related to getrefcount calls:

FAILED tests/test_common.py::TestGenericStruct::test_generic_struct_info_cached[json] - assert 3 == 4
FAILED tests/test_common.py::TestGenericStruct::test_generic_struct_info_cached[msgpack] - assert 3 == 4
FAILED tests/test_common.py::TestGenericDataclassOrAttrs::test_generic_info_cached[dataclass-json] - assert 3 == 4
FAILED tests/test_common.py::TestGenericDataclassOrAttrs::test_generic_info_cached[dataclass-msgpack] - assert 3 == 4
FAILED tests/test_convert.py::TestConvert::test_custom_input_type_works_with_any - assert 2 == 3
FAILED tests/test_convert.py::TestConvert::test_custom_input_type_works_with_custom - assert 2 == 3
FAILED tests/test_convert.py::TestConvert::test_custom_input_type_works_with_dec_hook - assert 1 == 2
FAILED tests/test_convert.py::TestInt::test_int_subclass - assert 2 == 3
FAILED tests/test_convert.py::TestBinary::test_bytes_subclass - AssertionError: assert 1 == 2
FAILED tests/test_convert.py::TestEnum::test_int_enum_int_subclass - assert 1 == 2
FAILED tests/test_json.py::TestDatetime::test_decode_timezone_cache - assert 2 == 3
FAILED tests/test_json.py::TestStruct::test_decode_struct - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_decode_memoryview_zerocopy[bytes] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_decode_memoryview_zerocopy[memoryview] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_vartuple_lengths[1] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_vartuple_lengths[31] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_vartuple_lengths[32] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_vartuple_lengths[255] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_vartuple_lengths[256] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_vartuple_lengths[65535] - AssertionError: assert 2 == 3
FAILED tests/test_msgpack.py::TestTypedDecoder::test_vartuple_lengths[65536] - AssertionError: assert 2 == 3
FAILED tests/test_struct.py::test_struct_reference_counting - assert 2 == 3

To run it I do:

$ python -VV
Python 3.14.0b1+ (heads/3.14:2a089244f0d, May 26 2025, 08:38:42) [Clang 15.0.0 (clang-1500.3.9.4)]
$ python -m pytest -s -m "not mypy and not pyright"

That's the latest tip of the 3.14 branch.

JelleZijlstra · 2025-05-26T16:56:43Z

The failures you post feel like they wouldn't be related to retrieving annotations; the code I'm changing is just in gathering annotations at class creation time, and whatever is happening in those tests is after the class is already created.

JelleZijlstra · 2025-05-26T17:05:52Z

Oh actually this is because of a bug in b1 that I fixed (python/cpython#133701); the fix will be in b2 which is about to go out.

I can reproduce it with the following change in the test:

$ git diff
diff --git a/tests/test_common.py b/tests/test_common.py
index 38898be..1c4c969 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -2099,6 +2099,7 @@ class TestTypedDict:
 
         class Ex(Base, total=False):
             c: str
+        Ex.__annotations__ = {"c": "str"}
 
         dec = proto.Decoder(Ex)

I do think that indicates a bug in msgspec; presumably it shouldn't crash even if people mess with the __annotations__ manually. I'll see if I can submit a fix.

hroncok · 2025-05-26T17:20:21Z

The failures occurred on b1 indeed.

Fixes at least some of the failures reported in: jcrist#852 (comment) These were exposed by a bug in 3.14b1 where TypedDict reported incorrect `__annotations__` but correct `__required_keys__`. msgspec would crash in this case. The bug is reproducible on earlier Python versions by manually manipulating attributes on a TypedDict class. It's a pretty marginal bug but I would argue the extension should be robust to this sort of edge case.

JelleZijlstra · 2025-05-26T17:50:55Z

#853 for that one.

hroncok · 2025-05-26T18:37:02Z

There are a lot of failures related to sys.getrefcount() but that seems to be an unrelated issue.

I opened #854

ncoghlan · 2025-08-22T03:14:00Z

I've confirmed via local testing that this PR fixes the Python 3.14 compatibility issue I noted in lmstudio-ai/lmstudio-python#153

ngoldbaum · 2025-09-12T17:41:09Z

Ping @jcrist - we're getting close to the final release date of Python 3.14. It'd be nice to have this merged to unblock further work to add 3.14 support here and in downstream packages that use msgspec.

ngoldbaum · 2025-10-07T21:34:15Z

Another ping here. I know @kumaraditya303 has a followup for this to add support for the free-threaded build which he plans to send in as soon as this PR is merged.

ofek · 2025-10-08T15:44:47Z

We are also dependent on this library and eager to upgrade.

btakita · 2025-10-10T16:54:17Z

Is @kumaraditya303's free-thread branch at
https://github.com/kumaraditya303/msgspec/tree/thread-safe?

stefanor · 2025-10-12T11:18:25Z

There are a lot of failures related to sys.getrefcount() but that seems to be an unrelated issue.

Those are also to be expected for Python 3.14. There is a new GC that will count a number of references, so any unit tests depending on sys.getrefcount() will have to deal with different values before and after 3.14. I've seen lots of if...else... branches in other libraries with similar tests.

ncoghlan · 2025-10-13T13:11:10Z

#854 is a draft PR to tackle the refcount tests just by allowing more relaxed measurements in general.

Original patch in jcrist#852.

kumaraditya303 · 2025-10-14T15:13:30Z

Is @kumaraditya303's free-thread branch at
https://github.com/kumaraditya303/msgspec/tree/thread-safe?

Yes, I created #877 for adding free-threading support.

ofek · 2025-10-15T17:03:26Z

I'm in talks with Jim about co-maintenance and should hopefully hear back in the next few days. If all goes well I plan to merge and release everything rapidly.

ofek · 2025-10-19T21:30:30Z



+if sys.version_info >= (3, 10):
+    from inspect import get_annotations as _get_class_annotations


We can't use this module as it introduces a large regression in terms of startup overhead:

❯ docker run --rm -it python:3.13 bash root@fe224bc3d8c0:/# pip install -qqq msgspec root@fe224bc3d8c0:/# python -m timeit -n 1 -r 1 "import msgspec" 1 loop, best of 1: 11.7 msec per loop root@fe224bc3d8c0:/# python -m timeit -n 1 -r 1 "import inspect" 1 loop, best of 1: 7.84 msec per loop

It's worth noting that as of 3.14 this function moved to annotationlib (which your C code imports directly) and inspect re-exports it. That module loads twice as fast but ideally we wouldn't incur any unnecessary overhead:

❯ docker run --rm -it python:3.14 bash root@8130942e2641:/# python -m timeit -n 1 -r 1 "import annotationlib" 1 loop, best of 1: 3.34 msec per loop

How would you recommend we proceed? I'm going to merge but this will be considered a known regression and will have to be fixed in a patch release right after.

Discussion in #880

ofek · 2025-10-19T21:38:33Z

Merging, thanks a lot!

ofek · 2025-10-19T21:49:24Z

Here's the issue tracking the performance regression #880

* Fix crash when TypedDict contains incorrect metadata (jcrist#853) * Fix annotations support on 3.14 (jcrist#852) * Relax all getrefcount tests to allow lower numbers (jcrist#854) * Add 3.14 to CI (jcrist#888) * add free-threading support (jcrist#877) Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> * Enable Python 3.14 tests in CI Remove cp314-* from CIBW_TEST_SKIP to allow Python 3.14 tests to run. Previously, 3.14 wheels were built but tests were skipped. --------- Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com> Co-authored-by: Miro Hrončok <miro@hroncok.cz> Co-authored-by: Ofek Lev <ofekmeister@gmail.com> Co-authored-by: Kumar Aditya <kumaraditya@python.org>

Fix annotations support on 3.14

89ecb0b

With this change, the tests run for me on a local build of Python 3.14. There are a lot of failures related to sys.getrefcount() but that seems to be an unrelated issue. Closes jcrist#810. Fixes jcrist#651. Fixes jcrist#795.

JelleZijlstra mentioned this pull request May 26, 2025

Python 3.14: Call __annotate__ on type objects to get annotations #810

Closed

JelleZijlstra commented May 26, 2025

View reviewed changes

JelleZijlstra mentioned this pull request May 26, 2025

Fix crash when TypedDict contains incorrect metadata #853

Merged

This was referenced Aug 19, 2025

Struct fields aren't discovered in Python 3.14 #847

Closed

Python 3.14: compatibility issue with default lazy annotations lmstudio-ai/lmstudio-python#153

Open

return42 mentioned this pull request Oct 8, 2025

Update annotation parsing to work with PEP 649 in Python 3.14 #651

Closed

harshil21 mentioned this pull request Oct 8, 2025

Migrate to Python 3.14 free threaded NCSU-High-Powered-Rocketry-Club/AirbrakesV2#230

Closed

mbsantiago mentioned this pull request Oct 13, 2025

msgspec.json.decode fails with KeyError when decoding dataclasses on Python 3.14 #876

Closed

manzt added a commit to marimo-team/msgspec that referenced this pull request Oct 13, 2025

Python 3.14 annotations support fix

cc0abc0

Original patch in jcrist#852.

manzt added a commit to marimo-team/msgspec that referenced this pull request Oct 13, 2025

Python 3.14 annotations support fix

ba4961a

Original patch in jcrist#852.

manzt mentioned this pull request Oct 13, 2025

Python 3.14 annotations support fix marimo-team/msgspec#5

Closed

kumaraditya303 mentioned this pull request Oct 14, 2025

add free-threading support #877

Merged

sobolevn mentioned this pull request Oct 16, 2025

Add another maintainer? #875

Closed

ofek approved these changes Oct 19, 2025

View reviewed changes

ofek merged commit 26cc7e7 into jcrist:main Oct 19, 2025

ofek mentioned this pull request Oct 19, 2025

Startup performance regression #880

Closed

This was referenced Oct 19, 2025

Fix linter #881

Merged

Investigate inlining functions from annotationlib #883

Open

manzt pushed a commit to marimo-team/msgspec that referenced this pull request Nov 14, 2025

Fix annotations support on 3.14 (jcrist#852)

f3d0584

manzt mentioned this pull request Nov 14, 2025

Cherry-pick Python 3.14 support and free-threading from upstream marimo-team/msgspec#8

Merged

ofek mentioned this pull request Nov 20, 2025

Optimize annotation lookups #940

Merged



		if sys.version_info >= (3, 10):
		from inspect import get_annotations as _get_class_annotations

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