msgspec: test on 3.13

HISTORY.md

@@ -27,6 +27,8 @@ Our backwards-compatibility policy can be found [here](https://github.com/python
 - Many preconf converters (_bson_, stdlib JSON, _cbor2_, _msgpack_, _msgspec_, _orjson_, _ujson_) skip unstructuring `int` and `str` enums,
   leaving them to the underlying libraries to handle with greater efficiency.
   ([#598](https://github.com/python-attrs/cattrs/pull/598))
+- The {class}`msgspec JSON preconf converter <cattrs.preconf.msgspec.MsgspecJsonConverter>` now handles dataclasses with private attributes more efficiently.
+  ([#624](https://github.com/python-attrs/cattrs/pull/624))
 - Literals containing enums are now unstructured properly, and their unstructuring is greatly optimized in the _bson_, stdlib JSON, _cbor2_, _msgpack_, _msgspec_, _orjson_ and _ujson_ preconf converters.
   ([#598](https://github.com/python-attrs/cattrs/pull/598))
 - Preconf converters now handle dictionaries with literal keys properly.

pyproject.toml

@@ -1,7 +1,7 @@
 [tool.black]
 skip-magic-trailing-comma = true
 
-[tool.pdm.dev-dependencies]
+[dependency-groups]
 lint = [
     "black>=24.2.0",
     "ruff>=0.0.277",
@@ -93,7 +93,7 @@ bson = [
     "pymongo>=4.4.0",
 ]
 msgspec = [
-    "msgspec>=0.18.5; implementation_name == \"cpython\"",
+    "msgspec>=0.19.0; implementation_name == \"cpython\"",
 ]
 
 [tool.pytest.ini_options]

src/cattrs/preconf/msgspec.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from base64 import b64decode
+from dataclasses import is_dataclass
 from datetime import date, datetime
 from enum import Enum
 from functools import partial
@@ -13,15 +14,7 @@
 from msgspec import Struct, convert, to_builtins
 from msgspec.json import Encoder, decode
 
-from .._compat import (
-    fields,
-    get_args,
-    get_origin,
-    has,
-    is_bare,
-    is_mapping,
-    is_sequence,
-)
+from .._compat import fields, get_args, get_origin, is_bare, is_mapping, is_sequence
 from ..cols import is_namedtuple
 from ..converters import BaseConverter, Converter
 from ..dispatch import UnstructureHook
@@ -104,11 +97,20 @@ def configure_passthroughs(converter: Converter) -> None:
     """Configure optimizing passthroughs.
 
     A passthrough is when we let msgspec handle something automatically.
+
+    .. versionchanged:: 25.1.0
+        Dataclasses with private attributes are now passed through.
     """
     converter.register_unstructure_hook(bytes, to_builtins)
     converter.register_unstructure_hook_factory(is_mapping, mapping_unstructure_factory)
     converter.register_unstructure_hook_factory(is_sequence, seq_unstructure_factory)
-    converter.register_unstructure_hook_factory(has, msgspec_attrs_unstructure_factory)
+    converter.register_unstructure_hook_factory(
+        attrs_has, msgspec_attrs_unstructure_factory
+    )
+    converter.register_unstructure_hook_factory(
+        is_dataclass,
+        partial(msgspec_attrs_unstructure_factory, msgspec_skips_private=False),
+    )
     converter.register_unstructure_hook_factory(
         is_namedtuple, namedtuple_unstructure_factory
     )
@@ -154,16 +156,21 @@ def mapping_unstructure_factory(type, converter: BaseConverter) -> UnstructureHo
 
 
 def msgspec_attrs_unstructure_factory(
-    type: Any, converter: Converter
+    type: Any, converter: Converter, msgspec_skips_private: bool = True
 ) -> UnstructureHook:
-    """Choose whether to use msgspec handling or our own."""
+    """Choose whether to use msgspec handling or our own.
+
+    Args:
+        msgspec_skips_private: Whether the msgspec library skips unstructuring
+            private attributes, making us do the work.
+    """
     origin = get_origin(type)
     attribs = fields(origin or type)
     if attrs_has(type) and any(isinstance(a.type, str) for a in attribs):
         resolve_types(type)
         attribs = fields(origin or type)
 
-    if any(
+    if msgspec_skips_private and any(
         attr.name.startswith("_")
         or (
             converter.get_unstructure_hook(attr.type, cache_result=False)

tests/conftest.py

@@ -37,5 +37,3 @@ def converter_cls(request):
     collect_ignore_glob.append("*_695.py")
 if platform.python_implementation() == "PyPy":
     collect_ignore_glob.append("*_cpython.py")
-if sys.version_info >= (3, 13):  # Remove when msgspec supports 3.13.
-    collect_ignore_glob.append("*test_msgspec_cpython.py")

tests/preconf/test_msgspec_cpython.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+from dataclasses import dataclass
 from enum import Enum
 from typing import (
     Any,
@@ -48,6 +49,18 @@ class C:
     _a: int
 
 
+@dataclass
+class DataclassA:
+    a: int
+
+
+@dataclass
+class DataclassC:
+    """Msgspec doesn't skip private attributes on dataclasses, so this should work OOB."""
+
+    _a: int
+
+
 class N(NamedTuple):
     a: int
 
@@ -107,6 +120,11 @@ def test_unstructure_pt_product_types(converter: Conv):
     assert not is_passthrough(converter.get_unstructure_hook(B))
     assert not is_passthrough(converter.get_unstructure_hook(C))
 
+    assert is_passthrough(converter.get_unstructure_hook(DataclassA))
+    assert is_passthrough(converter.get_unstructure_hook(DataclassC))
+
+    assert converter.unstructure(DataclassC(1)) == {"_a": 1}
+
     assert is_passthrough(converter.get_unstructure_hook(N))
     assert is_passthrough(converter.get_unstructure_hook(NA))
     assert not is_passthrough(converter.get_unstructure_hook(NC))

tox.ini

@@ -48,9 +48,6 @@ setenv =
     PDM_IGNORE_SAVED_PYTHON="1"
     COVERAGE_PROCESS_START={toxinidir}/pyproject.toml
     COVERAGE_CORE=sysmon
-commands_pre =
-    pdm sync -G ujson,msgpack,pyyaml,tomlkit,cbor2,bson,orjson,test
-    python -c 'import pathlib; pathlib.Path("{env_site_packages_dir}/cov.pth").write_text("import coverage; coverage.process_startup()")'
 
 [testenv:pypy3]
 setenv =