From 6266424580c6c222265bddceeaed57124b516ef7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sat, 6 Jan 2024 20:45:05 +0100
Subject: [PATCH 01/18] msgspec first pass

---
 docs/preconf.md                | 28 ++++++++++++-------
 pdm.lock                       | 48 +++++++++++++++++++++++++++++++--
 pyproject.toml                 |  3 +++
 src/cattr/gen.py               |  2 +-
 src/cattrs/converters.py       |  6 ++---
 src/cattrs/preconf/__init__.py | 14 ++++++++++
 src/cattrs/preconf/bson.py     |  3 ++-
 src/cattrs/preconf/cbor2.py    |  2 ++
 src/cattrs/preconf/json.py     |  2 ++
 src/cattrs/preconf/msgpack.py  |  2 ++
 src/cattrs/preconf/msgspec.py  | 49 ++++++++++++++++++++++++++++++++++
 src/cattrs/preconf/orjson.py   |  2 ++
 src/cattrs/preconf/pyyaml.py   |  3 ++-
 src/cattrs/preconf/tomlkit.py  |  3 ++-
 src/cattrs/preconf/ujson.py    |  2 ++
 tests/test_preconf.py          | 47 +++++++++++++++++++++++++-------
 16 files changed, 187 insertions(+), 29 deletions(-)
 create mode 100644 src/cattrs/preconf/msgspec.py

diff --git a/docs/preconf.md b/docs/preconf.md
index 48d75ce3..d805f7ab 100644
--- a/docs/preconf.md
+++ b/docs/preconf.md
@@ -56,15 +56,6 @@ Found at {mod}`cattrs.preconf.json`.
 Bytes are serialized as base 85 strings. Counters are serialized as dictionaries. Sets are serialized as lists, and deserialized back into sets. `datetime` s and `date` s are serialized as ISO 8601 strings.
 
 
-## _ujson_
-
-Found at {mod}`cattrs.preconf.ujson`.
-
-Bytes are serialized as base 85 strings. Sets are serialized as lists, and deserialized back into sets. `datetime` s and `date` s are serialized as ISO 8601 strings.
-
-`ujson` doesn't support integers less than -9223372036854775808, and greater than 9223372036854775807, nor does it support `float('inf')`.
-
-
 ## _orjson_
 
 Found at {mod}`cattrs.preconf.orjson`.
@@ -77,6 +68,25 @@ _orjson_ doesn't support integers less than -9223372036854775808, and greater th
 _orjson_ only supports mappings with string keys so mappings will have their keys stringified before serialization, and destringified during deserialization.
 
 
+## _msgspec_
+
+Found at {mod}`cattrs.preconf.msgspec`.
+Only JSON functionality is currently available, other formats supported by msgspec to follow in the future.
+
+Bytes are un/structured as base 64 strings directly by msgspec.
+_msgspec_ [encodes special float values](https://jcristharif.com/msgspec/supported-types.html#float) (`NaN, Inf, -Inf`) as `null`.
+`datetime` s and `date` s are passed through to be unstructured into RFC 3339 by _msgspec_ itself.
+
+
+## _ujson_
+
+Found at {mod}`cattrs.preconf.ujson`.
+
+Bytes are serialized as base 85 strings. Sets are serialized as lists, and deserialized back into sets. `datetime` s and `date` s are serialized as ISO 8601 strings.
+
+`ujson` doesn't support integers less than -9223372036854775808, and greater than 9223372036854775807, nor does it support `float('inf')`.
+
+
 ## _msgpack_
 
 Found at {mod}`cattrs.preconf.msgpack`.
diff --git a/pdm.lock b/pdm.lock
index a3c71a1d..faf1e3b7 100644
--- a/pdm.lock
+++ b/pdm.lock
@@ -2,10 +2,10 @@
 # It is not intended for manual editing.
 
 [metadata]
-groups = ["default", "bench", "bson", "cbor2", "docs", "lint", "msgpack", "orjson", "pyyaml", "test", "tomlkit", "ujson"]
+groups = ["default", "bench", "bson", "cbor2", "docs", "lint", "msgpack", "orjson", "pyyaml", "test", "tomlkit", "ujson", "msgspec"]
 strategy = ["cross_platform"]
 lock_version = "4.4.1"
-content_hash = "sha256:c48ae8c45873dfe03d3b677793be038f06b49fff96076a3f62731ed9b94b3de3"
+content_hash = "sha256:7f0761ff761a474620f436f9a8f8ef5b00a94cdd2d0669d3d6f241706ab27b95"
 
 [[package]]
 name = "alabaster"
@@ -615,6 +615,50 @@ files = [
     {file = "msgpack-1.0.5.tar.gz", hash = "sha256:c075544284eadc5cddc70f4757331d99dcbc16b2bbd4849d15f8aae4cf36d31c"},
 ]
 
+[[package]]
+name = "msgspec"
+version = "0.18.5"
+requires_python = ">=3.8"
+summary = "A fast serialization and validation library, with builtin support for JSON, MessagePack, YAML, and TOML."
+files = [
+    {file = "msgspec-0.18.5-cp310-cp310-macosx_10_9_x86_64.whl", hash = "sha256:50479d88f3c4e9c73b55fbe84dc14b1cee8cec753e9170bbeafe3f9837e9f7af"},
+    {file = "msgspec-0.18.5-cp310-cp310-macosx_11_0_arm64.whl", hash = "sha256:cf885edac512e464c70a5f4f93b6f778c83ea4b91d646b6d72f6f5ac950f268e"},
+    {file = "msgspec-0.18.5-cp310-cp310-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:773a38ead7832d171d1b9406bf42448a218245584af36e42c31f26d9f48a493a"},
+    {file = "msgspec-0.18.5-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:d5999eb65646b131f439ebb07c22446e8976b7fd8a312dca09ce6fa2c21162bb"},
+    {file = "msgspec-0.18.5-cp310-cp310-musllinux_1_1_aarch64.whl", hash = "sha256:a0ec78bd93684db61dfccf7a421b2e1a525b1a0546b4d8c4e339151be57d58a6"},
+    {file = "msgspec-0.18.5-cp310-cp310-musllinux_1_1_x86_64.whl", hash = "sha256:b547c7ad9786a79b0090a811d95d2d04063625a66fd96ed767cdfbabd8087c67"},
+    {file = "msgspec-0.18.5-cp310-cp310-win_amd64.whl", hash = "sha256:e4c2fc93a98afefd1a78e957ca63363a8e5fd1b58bf70a8d66413c8f2a4723a2"},
+    {file = "msgspec-0.18.5-cp311-cp311-macosx_10_9_x86_64.whl", hash = "sha256:ee1f9414523d9a53744d21a6a2b6a636d9008be016963148a2646b38132e11dd"},
+    {file = "msgspec-0.18.5-cp311-cp311-macosx_11_0_arm64.whl", hash = "sha256:0017f6af35a3959002df4c82af60c1df2160701529dd89b17df971fde5945257"},
+    {file = "msgspec-0.18.5-cp311-cp311-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:13da9df61745b7757070dae6e3476ab4e13bb9dd3e3d11b050dfcae540058bd1"},
+    {file = "msgspec-0.18.5-cp311-cp311-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:01ed3472a0508f88a25a9d3bccafb840110f0fc5eb493b4baa43646e4e7c75c2"},
+    {file = "msgspec-0.18.5-cp311-cp311-musllinux_1_1_aarch64.whl", hash = "sha256:f55c4610cb0514aef8b35bfd0682f4cc2d7efd5e9b58acf30abd90b2a2376b5d"},
+    {file = "msgspec-0.18.5-cp311-cp311-musllinux_1_1_x86_64.whl", hash = "sha256:8f7c0460aefdc8f01ea35f26e38c62b574bbf0b138ade860f557bbf9e9dac50c"},
+    {file = "msgspec-0.18.5-cp311-cp311-win_amd64.whl", hash = "sha256:024f880df7d2f8cfdb9f9904efa0f386d3692457159bd58f850c20f11c07d16f"},
+    {file = "msgspec-0.18.5-cp312-cp312-macosx_10_9_x86_64.whl", hash = "sha256:b3d206af4280172948d014d20b2cea7939784a99ea9a7ac943ce71100dbe8f98"},
+    {file = "msgspec-0.18.5-cp312-cp312-macosx_11_0_arm64.whl", hash = "sha256:261cc6e3a687e6f31b80056ab12f6adff3255f9b68b86d92b0b497f8b289c84c"},
+    {file = "msgspec-0.18.5-cp312-cp312-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:b6af133ba491a09ef8dcbc2d9904bcec220247e2067bb75d5d6daa12e0739d6c"},
+    {file = "msgspec-0.18.5-cp312-cp312-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:d318593e0ddc11b600552a470ec27baeb0b86a8e37903ac5ce7472ba0d6f7bf8"},
+    {file = "msgspec-0.18.5-cp312-cp312-musllinux_1_1_aarch64.whl", hash = "sha256:9a7b682cca3ba251a19cc769d38615ddd9551e086858decd950c156c2e79ecc1"},
+    {file = "msgspec-0.18.5-cp312-cp312-musllinux_1_1_x86_64.whl", hash = "sha256:b491b2549d22e11d7cfe34a231f9bd006cb6b71adefa070a070075d2f601e75c"},
+    {file = "msgspec-0.18.5-cp312-cp312-win_amd64.whl", hash = "sha256:c79e7115f0143688c5d866359e7b6b76dd1581a81c9aeac7805a9d6320e9f2ca"},
+    {file = "msgspec-0.18.5-cp38-cp38-macosx_10_9_x86_64.whl", hash = "sha256:c13e0a510bbd00cb29d193fceff55d1e17a99c9f97284cdbe61c15496c2f7803"},
+    {file = "msgspec-0.18.5-cp38-cp38-macosx_11_0_arm64.whl", hash = "sha256:f4eeb22921ca6cdfbf17ca874eccbe23eb010c89ffb3017b628940c37d53ce4a"},
+    {file = "msgspec-0.18.5-cp38-cp38-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:9420750f19c311e490db3edff9d153621c4989c582cf1be40c307c86d6cc2c1e"},
+    {file = "msgspec-0.18.5-cp38-cp38-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:6431305c645fb2a88a6da1fcec53dbaac61697f1219000b9589f9286532aabc0"},
+    {file = "msgspec-0.18.5-cp38-cp38-musllinux_1_1_aarch64.whl", hash = "sha256:b7b49cba0577edc8ac166263b5fec3619fe5a267805cfc041bccaf8a0c58ef05"},
+    {file = "msgspec-0.18.5-cp38-cp38-musllinux_1_1_x86_64.whl", hash = "sha256:3f387cabddf2dc26d6fa7f1a8158deefc8db9e0626eacebbe4875f421c66d574"},
+    {file = "msgspec-0.18.5-cp38-cp38-win_amd64.whl", hash = "sha256:482bdf77f3892dd603061b2b21ac6a4492bb797a552c92e833a41fe157162257"},
+    {file = "msgspec-0.18.5-cp39-cp39-macosx_10_9_x86_64.whl", hash = "sha256:f290bfe7e21e8069890d101d8a060500b22a3aeb7860274644c4ec9240ddbedc"},
+    {file = "msgspec-0.18.5-cp39-cp39-macosx_11_0_arm64.whl", hash = "sha256:0027fba5362a3cb1bdd5503709aa2dbffad22dffd50f415086ed5f74f229ead9"},
+    {file = "msgspec-0.18.5-cp39-cp39-manylinux_2_17_aarch64.manylinux2014_aarch64.whl", hash = "sha256:bd8a64da668b4eeef4b21dcecc640ed6950db661e2ea42ae52bbac5a2dbffb3a"},
+    {file = "msgspec-0.18.5-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl", hash = "sha256:be2440fa5699e1b3062d17fdfd8c6a459d72bb4edbce403353af6f39c8c5a6fa"},
+    {file = "msgspec-0.18.5-cp39-cp39-musllinux_1_1_aarch64.whl", hash = "sha256:eccba21248f90f332335b109e89685e79940367974812cd13975313f480f3dd8"},
+    {file = "msgspec-0.18.5-cp39-cp39-musllinux_1_1_x86_64.whl", hash = "sha256:c30fadc1a1118097920dd868e42469fed32c7078ca2feff2fc19e7c017065322"},
+    {file = "msgspec-0.18.5-cp39-cp39-win_amd64.whl", hash = "sha256:fae28faef5fd61847930d8e86fd83c18f991a338efd8fbf69c1d35d42c652f41"},
+    {file = "msgspec-0.18.5.tar.gz", hash = "sha256:8e545651531f2d01b983d0ac0c7f3b6d99674267ff261b5f344f5016160b5608"},
+]
+
 [[package]]
 name = "mypy-extensions"
 version = "1.0.0"
diff --git a/pyproject.toml b/pyproject.toml
index 32101045..9f3530ab 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -94,6 +94,9 @@ cbor2 = [
 bson = [
     "pymongo>=4.4.0",
 ]
+msgspec = [
+    "msgspec>=0.18.5",
+]
 
 [tool.pytest.ini_options]
 addopts = "-l --benchmark-sort=fullname --benchmark-warmup=true --benchmark-warmup-iterations=5  --benchmark-group-by=fullname"
diff --git a/src/cattr/gen.py b/src/cattr/gen.py
index 660d4d53..a41c2d11 100644
--- a/src/cattr/gen.py
+++ b/src/cattr/gen.py
@@ -1,5 +1,4 @@
 from cattrs.gen import (
-    AttributeOverride,
     make_dict_structure_fn,
     make_dict_unstructure_fn,
     make_hetero_tuple_unstructure_fn,
@@ -8,6 +7,7 @@
     make_mapping_unstructure_fn,
     override,
 )
+from cattrs.gen._consts import AttributeOverride
 
 __all__ = [
     "AttributeOverride",
diff --git a/src/cattrs/converters.py b/src/cattrs/converters.py
index 172a7584..d9a18241 100644
--- a/src/cattrs/converters.py
+++ b/src/cattrs/converters.py
@@ -750,12 +750,10 @@ def _get_dis_func(
     ) -> Callable[[Any], type]:
         """Fetch or try creating a disambiguation function for a union."""
         union_types = union.__args__
-        if NoneType in union_types:  # type: ignore
+        if NoneType in union_types:
             # We support unions of attrs classes and NoneType higher in the
             # logic.
-            union_types = tuple(
-                e for e in union_types if e is not NoneType  # type: ignore
-            )
+            union_types = tuple(e for e in union_types if e is not NoneType)
 
         # TODO: technically both disambiguators could support TypedDicts and
         # dataclasses...
diff --git a/src/cattrs/preconf/__init__.py b/src/cattrs/preconf/__init__.py
index 760ae115..7f747073 100644
--- a/src/cattrs/preconf/__init__.py
+++ b/src/cattrs/preconf/__init__.py
@@ -1,7 +1,21 @@
 from datetime import datetime
+from typing import Any, Callable, ParamSpec, TypeVar
 
 
 def validate_datetime(v, _):
     if not isinstance(v, datetime):
         raise Exception(f"Expected datetime, got {v}")
     return v
+
+
+T = TypeVar("T")
+P = ParamSpec("P")
+
+
+def wrap(inner: Callable[P, Any]) -> Callable[[Callable[..., T]], Callable[P, T]]:
+    """Wrap a `Converter` `__init__` in a type-safe way."""
+
+    def impl(x: Callable[..., T]) -> Callable[P, T]:
+        return inner
+
+    return impl
diff --git a/src/cattrs/preconf/bson.py b/src/cattrs/preconf/bson.py
index 6fc6d72a..cab125be 100644
--- a/src/cattrs/preconf/bson.py
+++ b/src/cattrs/preconf/bson.py
@@ -11,7 +11,7 @@
 from ..converters import BaseConverter, Converter
 from ..dispatch import StructureHook
 from ..strategies import configure_union_passthrough
-from . import validate_datetime
+from . import validate_datetime, wrap
 
 T = TypeVar("T")
 
@@ -93,6 +93,7 @@ def gen_structure_mapping(cl: Any) -> StructureHook:
     converter.register_structure_hook(date, lambda v, _: date.fromisoformat(v))
 
 
+@wrap(BsonConverter)
 def make_converter(*args: Any, **kwargs: Any) -> BsonConverter:
     kwargs["unstruct_collection_overrides"] = {
         AbstractSet: list,
diff --git a/src/cattrs/preconf/cbor2.py b/src/cattrs/preconf/cbor2.py
index 444014b4..414d19ce 100644
--- a/src/cattrs/preconf/cbor2.py
+++ b/src/cattrs/preconf/cbor2.py
@@ -8,6 +8,7 @@
 
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
+from . import wrap
 
 T = TypeVar("T")
 
@@ -36,6 +37,7 @@ def configure_converter(converter: BaseConverter):
     configure_union_passthrough(Union[str, bool, int, float, None, bytes], converter)
 
 
+@wrap(Cbor2Converter)
 def make_converter(*args: Any, **kwargs: Any) -> Cbor2Converter:
     kwargs["unstruct_collection_overrides"] = {
         AbstractSet: list,
diff --git a/src/cattrs/preconf/json.py b/src/cattrs/preconf/json.py
index e4d52a3c..b9b1b1cf 100644
--- a/src/cattrs/preconf/json.py
+++ b/src/cattrs/preconf/json.py
@@ -8,6 +8,7 @@
 
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
+from . import wrap
 
 T = TypeVar("T")
 
@@ -40,6 +41,7 @@ def configure_converter(converter: BaseConverter):
     configure_union_passthrough(Union[str, bool, int, float, None, bytes], converter)
 
 
+@wrap(JsonConverter)
 def make_converter(*args: Any, **kwargs: Any) -> JsonConverter:
     kwargs["unstruct_collection_overrides"] = {
         AbstractSet: list,
diff --git a/src/cattrs/preconf/msgpack.py b/src/cattrs/preconf/msgpack.py
index 2e7470b6..2a63ccd8 100644
--- a/src/cattrs/preconf/msgpack.py
+++ b/src/cattrs/preconf/msgpack.py
@@ -8,6 +8,7 @@
 
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
+from . import wrap
 
 T = TypeVar("T")
 
@@ -40,6 +41,7 @@ def configure_converter(converter: BaseConverter):
     configure_union_passthrough(Union[str, bool, int, float, None, bytes], converter)
 
 
+@wrap(MsgpackConverter)
 def make_converter(*args: Any, **kwargs: Any) -> MsgpackConverter:
     kwargs["unstruct_collection_overrides"] = {
         AbstractSet: list,
diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
new file mode 100644
index 00000000..7b257070
--- /dev/null
+++ b/src/cattrs/preconf/msgspec.py
@@ -0,0 +1,49 @@
+"""Preconfigured converters for msgspec."""
+from __future__ import annotations
+
+from base64 import b64decode
+from datetime import date, datetime
+from typing import Any, Callable, ParamSpec, TypeVar, Union
+
+from msgspec.json import decode, encode
+
+from ..converters import BaseConverter, Converter
+from ..strategies import configure_union_passthrough
+
+T = TypeVar("T")
+P = ParamSpec("P")
+
+
+def wrap(inner: Callable[P, Any]) -> Callable[[Callable[..., T]], Callable[P, T]]:
+    def impl(x: Callable[..., T]) -> Callable[P, T]:
+        return inner
+
+    return impl
+
+
+class MsgspecJsonConverter(Converter):
+    def dumps(self, obj: Any, unstructure_as: Any = None, **kwargs: Any) -> bytes:
+        return encode(self.unstructure(obj, unstructure_as=unstructure_as), **kwargs)
+
+    def loads(self, data: bytes, cl: type[T], **kwargs: Any) -> T:
+        return self.structure(decode(data, **kwargs), cl)
+
+
+def configure_converter(converter: BaseConverter) -> None:
+    """Configure the converter for the msgspec library.
+
+    * bytes are serialized as base64 strings, directly by msgspec
+    * datetimes and dates are passed through to be serialized as RFC 3339 directly
+    * union passthrough configured for str, bool, int, float and None
+    """
+    converter.register_structure_hook(bytes, lambda v, _: b64decode(v))
+    converter.register_structure_hook(datetime, lambda v, _: datetime.fromisoformat(v))
+    converter.register_structure_hook(date, lambda v, _: date.fromisoformat(v))
+    configure_union_passthrough(Union[str, bool, int, float, None], converter)
+
+
+@wrap(MsgspecJsonConverter)
+def make_converter(*args: Any, **kwargs: Any) -> MsgspecJsonConverter:
+    res = MsgspecJsonConverter(*args, **kwargs)
+    configure_converter(res)
+    return res
diff --git a/src/cattrs/preconf/orjson.py b/src/cattrs/preconf/orjson.py
index fcd380b9..8df76a78 100644
--- a/src/cattrs/preconf/orjson.py
+++ b/src/cattrs/preconf/orjson.py
@@ -11,6 +11,7 @@
 from ..converters import BaseConverter, Converter
 from ..fns import identity
 from ..strategies import configure_union_passthrough
+from . import wrap
 
 T = TypeVar("T")
 
@@ -69,6 +70,7 @@ def key_handler(v):
     configure_union_passthrough(Union[str, bool, int, float, None], converter)
 
 
+@wrap(OrjsonConverter)
 def make_converter(*args: Any, **kwargs: Any) -> OrjsonConverter:
     kwargs["unstruct_collection_overrides"] = {
         AbstractSet: list,
diff --git a/src/cattrs/preconf/pyyaml.py b/src/cattrs/preconf/pyyaml.py
index 091c1d37..19314ee1 100644
--- a/src/cattrs/preconf/pyyaml.py
+++ b/src/cattrs/preconf/pyyaml.py
@@ -8,7 +8,7 @@
 
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
-from . import validate_datetime
+from . import validate_datetime, wrap
 
 T = TypeVar("T")
 
@@ -49,6 +49,7 @@ def configure_converter(converter: BaseConverter):
     )
 
 
+@wrap(PyyamlConverter)
 def make_converter(*args: Any, **kwargs: Any) -> PyyamlConverter:
     kwargs["unstruct_collection_overrides"] = {
         FrozenSetSubscriptable: list,
diff --git a/src/cattrs/preconf/tomlkit.py b/src/cattrs/preconf/tomlkit.py
index 8cdfeac7..10daf49d 100644
--- a/src/cattrs/preconf/tomlkit.py
+++ b/src/cattrs/preconf/tomlkit.py
@@ -12,7 +12,7 @@
 
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
-from . import validate_datetime
+from . import validate_datetime, wrap
 
 T = TypeVar("T")
 _enum_value_getter = attrgetter("_value_")
@@ -73,6 +73,7 @@ def key_handler(k: bytes):
     )
 
 
+@wrap(TomlkitConverter)
 def make_converter(*args: Any, **kwargs: Any) -> TomlkitConverter:
     kwargs["unstruct_collection_overrides"] = {
         AbstractSet: list,
diff --git a/src/cattrs/preconf/ujson.py b/src/cattrs/preconf/ujson.py
index b6de8e85..0644186b 100644
--- a/src/cattrs/preconf/ujson.py
+++ b/src/cattrs/preconf/ujson.py
@@ -9,6 +9,7 @@
 
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
+from . import wrap
 
 T = TypeVar("T")
 
@@ -41,6 +42,7 @@ def configure_converter(converter: BaseConverter):
     configure_union_passthrough(Union[str, bool, int, float, None], converter)
 
 
+@wrap(UjsonConverter)
 def make_converter(*args: Any, **kwargs: Any) -> UjsonConverter:
     kwargs["unstruct_collection_overrides"] = {
         AbstractSet: list,
diff --git a/tests/test_preconf.py b/tests/test_preconf.py
index f547e8de..306d0803 100644
--- a/tests/test_preconf.py
+++ b/tests/test_preconf.py
@@ -48,6 +48,7 @@
 from cattrs.preconf.cbor2 import make_converter as cbor2_make_converter
 from cattrs.preconf.json import make_converter as json_make_converter
 from cattrs.preconf.msgpack import make_converter as msgpack_make_converter
+from cattrs.preconf.msgspec import make_converter as msgspec_make_converter
 from cattrs.preconf.pyyaml import make_converter as pyyaml_make_converter
 from cattrs.preconf.tomlkit import make_converter as tomlkit_make_converter
 from cattrs.preconf.ujson import make_converter as ujson_make_converter
@@ -296,7 +297,6 @@ def test_stdlib_json_converter_unstruct_collection_overrides(everything: Everyth
         include_bytes=False,
         include_datetimes=False,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -314,7 +314,6 @@ def test_stdlib_json_unions(union_and_val: tuple, detailed_validation: bool):
         include_strings=False,
         include_bytes=False,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -376,7 +375,6 @@ def test_ujson_converter_unstruct_collection_overrides(everything: Everything):
         include_bytes=False,
         include_datetimes=False,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -445,7 +443,6 @@ def test_orjson_converter_unstruct_collection_overrides(everything: Everything):
         include_bytes=False,
         include_datetimes=False,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -494,7 +491,6 @@ def test_msgpack_converter_unstruct_collection_overrides(everything: Everything)
     union_and_val=native_unions(
         include_datetimes=False,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -569,7 +565,6 @@ def test_bson_converter_unstruct_collection_overrides(everything: Everything):
     union_and_val=native_unions(
         include_objectids=True,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -609,8 +604,7 @@ def test_pyyaml_converter_unstruct_collection_overrides(everything: Everything):
 
 @given(
     union_and_val=native_unions(
-        include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
+        include_bools=sys.version_info[:2] != (3, 8)  # Literal issues on 3.8
     ),
     detailed_validation=...,
 )
@@ -698,7 +692,6 @@ def test_tomlkit_converter_unstruct_collection_overrides(everything: Everything)
         include_bytes=False,
         include_datetimes=False,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -750,7 +743,6 @@ def test_cbor2_converter_unstruct_collection_overrides(everything: Everything):
     union_and_val=native_unions(
         include_datetimes=False,
         include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
-        include_literals=sys.version_info >= (3, 8),
     ),
     detailed_validation=...,
 )
@@ -760,3 +752,38 @@ def test_cbor2_unions(union_and_val: tuple, detailed_validation: bool):
     type, val = union_and_val
 
     assert converter.structure(val, type) == val
+
+
+@given(everythings(allow_inf=False))
+def test_msgspec_json_converter(everything: Everything):
+    converter = msgspec_make_converter()
+    raw = converter.dumps(everything)
+    assert converter.loads(raw, Everything) == everything
+
+
+@given(everythings(allow_inf=False))
+def test_msgspec_json_unstruct_collection_overrides(everything: Everything):
+    """Ensure collection overrides work."""
+    converter = msgspec_make_converter(
+        unstruct_collection_overrides={AbstractSet: sorted}
+    )
+    raw = converter.unstructure(everything)
+    assert raw["a_set"] == sorted(raw["a_set"])
+    assert raw["a_mutable_set"] == sorted(raw["a_mutable_set"])
+    assert raw["a_frozenset"] == sorted(raw["a_frozenset"])
+
+
+@given(
+    union_and_val=native_unions(
+        include_datetimes=False,
+        include_bytes=False,
+        include_bools=sys.version_info[:2] != (3, 8),  # Literal issues on 3.8
+    ),
+    detailed_validation=...,
+)
+def test_msgspec_json_unions(union_and_val: tuple, detailed_validation: bool):
+    """Native union passthrough works."""
+    converter = msgspec_make_converter(detailed_validation=detailed_validation)
+    type, val = union_and_val
+
+    assert converter.structure(val, type) == val

From 428d952b7afe83ce257649d4c3ee9cda4fe9e26c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sat, 6 Jan 2024 20:52:44 +0100
Subject: [PATCH 02/18] Fix typing import

---
 src/cattrs/preconf/__init__.py | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/cattrs/preconf/__init__.py b/src/cattrs/preconf/__init__.py
index 7f747073..9b4eb359 100644
--- a/src/cattrs/preconf/__init__.py
+++ b/src/cattrs/preconf/__init__.py
@@ -1,5 +1,11 @@
+import sys
 from datetime import datetime
-from typing import Any, Callable, ParamSpec, TypeVar
+from typing import Any, Callable, TypeVar
+
+if sys.version_info[:2] < (3, 10):
+    from typing_extensions import ParamSpec
+else:
+    from typing import ParamSpec
 
 
 def validate_datetime(v, _):

From 07d40ac0a966728744762b95488938a8938cbf6a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 01:53:55 +0100
Subject: [PATCH 03/18] Test carefully for PyPy

---
 tests/test_preconf.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tests/test_preconf.py b/tests/test_preconf.py
index 306d0803..adce4945 100644
--- a/tests/test_preconf.py
+++ b/tests/test_preconf.py
@@ -48,7 +48,6 @@
 from cattrs.preconf.cbor2 import make_converter as cbor2_make_converter
 from cattrs.preconf.json import make_converter as json_make_converter
 from cattrs.preconf.msgpack import make_converter as msgpack_make_converter
-from cattrs.preconf.msgspec import make_converter as msgspec_make_converter
 from cattrs.preconf.pyyaml import make_converter as pyyaml_make_converter
 from cattrs.preconf.tomlkit import make_converter as tomlkit_make_converter
 from cattrs.preconf.ujson import make_converter as ujson_make_converter
@@ -756,6 +755,8 @@ def test_cbor2_unions(union_and_val: tuple, detailed_validation: bool):
 
 @given(everythings(allow_inf=False))
 def test_msgspec_json_converter(everything: Everything):
+    from cattrs.preconf.msgspec import make_converter as msgspec_make_converter
+
     converter = msgspec_make_converter()
     raw = converter.dumps(everything)
     assert converter.loads(raw, Everything) == everything
@@ -764,6 +765,8 @@ def test_msgspec_json_converter(everything: Everything):
 @given(everythings(allow_inf=False))
 def test_msgspec_json_unstruct_collection_overrides(everything: Everything):
     """Ensure collection overrides work."""
+    from cattrs.preconf.msgspec import make_converter as msgspec_make_converter
+
     converter = msgspec_make_converter(
         unstruct_collection_overrides={AbstractSet: sorted}
     )
@@ -783,6 +786,8 @@ def test_msgspec_json_unstruct_collection_overrides(everything: Everything):
 )
 def test_msgspec_json_unions(union_and_val: tuple, detailed_validation: bool):
     """Native union passthrough works."""
+    from cattrs.preconf.msgspec import make_converter as msgspec_make_converter
+
     converter = msgspec_make_converter(detailed_validation=detailed_validation)
     type, val = union_and_val
 

From cfe6ed4a283e97e36ffa922c9c14fecfeb2c07a8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 01:54:26 +0100
Subject: [PATCH 04/18] Docs

---
 HISTORY.md                    |  5 +++++
 docs/cattrs.preconf.rst       |  8 ++++++++
 docs/preconf.md               |  5 +++++
 src/cattrs/preconf/msgspec.py | 12 +++++-------
 4 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/HISTORY.md b/HISTORY.md
index e7737d7c..a592e44b 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -17,6 +17,9 @@ Our backwards-compatibility policy can be found [here](https://github.com/python
   ([#473](https://github.com/python-attrs/cattrs/pull/473))
 - Introduce {meth}`BaseConverter.get_structure_hook` and {meth}`BaseConverter.get_unstructure_hook` methods.
   ([#432](https://github.com/python-attrs/cattrs/issues/432) [#472](https://github.com/python-attrs/cattrs/pull/472))
+- Introduce the [_msgspec_](https://jcristharif.com/msgspec/) {mod}`preconf converter <cattrs.preconf.msgspec>`.
+  Only JSON is supported for now, with other formats supported by _msgspec_ to come later.
+  ([#481](https://github.com/python-attrs/cattrs/pull/481))
 - The default union handler now properly takes renamed fields into account.
   ([#472](https://github.com/python-attrs/cattrs/pull/472))
 - The default union handler now also handles dataclasses.
@@ -25,6 +28,8 @@ Our backwards-compatibility policy can be found [here](https://github.com/python
   ([#452](https://github.com/python-attrs/cattrs/pull/452))
 - The `include_subclasses` strategy now fetches the member hooks from the converter (making use of converter defaults) if overrides are not provided, instead of generating new hooks with no overrides.
   ([#429](https://github.com/python-attrs/cattrs/issues/429) [#472](https://github.com/python-attrs/cattrs/pull/472))
+- The preconf `make_converter` factories are now correctly typed.
+  ([#481](https://github.com/python-attrs/cattrs/pull/481))
 - The {class}`orjson preconf converter <cattrs.preconf.orjson.OrjsonConverter>` now passes through dates and datetimes to orjson while unstructuring, greatly improving speed.
   ([#463](https://github.com/python-attrs/cattrs/pull/463))
 - `cattrs.gen` generators now attach metadata to the generated functions, making them introspectable.
diff --git a/docs/cattrs.preconf.rst b/docs/cattrs.preconf.rst
index 61a94d2c..6b8f9312 100644
--- a/docs/cattrs.preconf.rst
+++ b/docs/cattrs.preconf.rst
@@ -41,6 +41,14 @@ cattrs.preconf.msgpack module
    :undoc-members:
    :show-inheritance:
 
+cattrs.preconf.msgspec module
+-----------------------------
+
+.. automodule:: cattrs.preconf.msgspec
+   :members:
+   :undoc-members:
+   :show-inheritance:
+
 cattrs.preconf.orjson module
 ----------------------------
 
diff --git a/docs/preconf.md b/docs/preconf.md
index d805f7ab..257243d1 100644
--- a/docs/preconf.md
+++ b/docs/preconf.md
@@ -70,6 +70,10 @@ _orjson_ only supports mappings with string keys so mappings will have their key
 
 ## _msgspec_
 
+```{versionadded} 24.1.0
+
+```
+
 Found at {mod}`cattrs.preconf.msgspec`.
 Only JSON functionality is currently available, other formats supported by msgspec to follow in the future.
 
@@ -77,6 +81,7 @@ Bytes are un/structured as base 64 strings directly by msgspec.
 _msgspec_ [encodes special float values](https://jcristharif.com/msgspec/supported-types.html#float) (`NaN, Inf, -Inf`) as `null`.
 `datetime` s and `date` s are passed through to be unstructured into RFC 3339 by _msgspec_ itself.
 
+_msgspec_ doesn't support PyPy.
 
 ## _ujson_
 
diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 7b257070..8a4b8f3d 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -3,29 +3,27 @@
 
 from base64 import b64decode
 from datetime import date, datetime
-from typing import Any, Callable, ParamSpec, TypeVar, Union
+from typing import Any, ParamSpec, TypeVar, Union
 
 from msgspec.json import decode, encode
 
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
+from . import wrap
 
 T = TypeVar("T")
 P = ParamSpec("P")
 
-
-def wrap(inner: Callable[P, Any]) -> Callable[[Callable[..., T]], Callable[P, T]]:
-    def impl(x: Callable[..., T]) -> Callable[P, T]:
-        return inner
-
-    return impl
+__all__ = ["MsgspecJsonConverter", "configure_converter", "make_converter"]
 
 
 class MsgspecJsonConverter(Converter):
     def dumps(self, obj: Any, unstructure_as: Any = None, **kwargs: Any) -> bytes:
+        """Unstructure and encode `obj` into JSON bytes."""
         return encode(self.unstructure(obj, unstructure_as=unstructure_as), **kwargs)
 
     def loads(self, data: bytes, cl: type[T], **kwargs: Any) -> T:
+        """Decode and structure `cl` from the provided JSON bytes."""
         return self.structure(decode(data, **kwargs), cl)
 
 

From ab55a72ad643525df4810e48beea7acef6090c8b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 02:09:19 +0100
Subject: [PATCH 05/18] Fix typing wrapper

---
 src/cattrs/preconf/__init__.py | 4 ++--
 src/cattrs/preconf/json.py     | 9 +++++----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/cattrs/preconf/__init__.py b/src/cattrs/preconf/__init__.py
index 9b4eb359..876576d1 100644
--- a/src/cattrs/preconf/__init__.py
+++ b/src/cattrs/preconf/__init__.py
@@ -18,10 +18,10 @@ def validate_datetime(v, _):
 P = ParamSpec("P")
 
 
-def wrap(inner: Callable[P, Any]) -> Callable[[Callable[..., T]], Callable[P, T]]:
+def wrap(_: Callable[P, Any]) -> Callable[[Callable[..., T]], Callable[P, T]]:
     """Wrap a `Converter` `__init__` in a type-safe way."""
 
     def impl(x: Callable[..., T]) -> Callable[P, T]:
-        return inner
+        return x
 
     return impl
diff --git a/src/cattrs/preconf/json.py b/src/cattrs/preconf/json.py
index b9b1b1cf..f4f5057a 100644
--- a/src/cattrs/preconf/json.py
+++ b/src/cattrs/preconf/json.py
@@ -4,8 +4,7 @@
 from json import dumps, loads
 from typing import Any, Type, TypeVar, Union
 
-from cattrs._compat import AbstractSet, Counter
-
+from .._compat import AbstractSet, Counter
 from ..converters import BaseConverter, Converter
 from ..strategies import configure_union_passthrough
 from . import wrap
@@ -25,10 +24,12 @@ def configure_converter(converter: BaseConverter):
     """
     Configure the converter for use with the stdlib json module.
 
-    * bytes are serialized as base64 strings
+    * bytes are serialized as base85 strings
     * datetimes are serialized as ISO 8601
     * counters are serialized as dicts
     * sets are serialized as lists
+    * union passthrough is configured for unions of strings, bools, ints,
+      floats and None
     """
     converter.register_unstructure_hook(
         bytes, lambda v: (b85encode(v) if v else b"").decode("utf8")
@@ -38,7 +39,7 @@ def configure_converter(converter: BaseConverter):
     converter.register_structure_hook(datetime, lambda v, _: datetime.fromisoformat(v))
     converter.register_unstructure_hook(date, lambda v: v.isoformat())
     converter.register_structure_hook(date, lambda v, _: date.fromisoformat(v))
-    configure_union_passthrough(Union[str, bool, int, float, None, bytes], converter)
+    configure_union_passthrough(Union[str, bool, int, float, None], converter)
 
 
 @wrap(JsonConverter)

From 605efc3e788eba393f0da54a3795cd4b2a5ca9c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 02:27:09 +0100
Subject: [PATCH 06/18] Fix PyPy CI some more

---
 tests/test_preconf.py |  3 +++
 tox.ini               | 17 ++++++-----------
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/tests/test_preconf.py b/tests/test_preconf.py
index adce4945..2f43873a 100644
--- a/tests/test_preconf.py
+++ b/tests/test_preconf.py
@@ -753,6 +753,7 @@ def test_cbor2_unions(union_and_val: tuple, detailed_validation: bool):
     assert converter.structure(val, type) == val
 
 
+@pytest.mark.skipif(python_implementation() == "PyPy", reason="no msgspec on PyPy")
 @given(everythings(allow_inf=False))
 def test_msgspec_json_converter(everything: Everything):
     from cattrs.preconf.msgspec import make_converter as msgspec_make_converter
@@ -762,6 +763,7 @@ def test_msgspec_json_converter(everything: Everything):
     assert converter.loads(raw, Everything) == everything
 
 
+@pytest.mark.skipif(python_implementation() == "PyPy", reason="no msgspec on PyPy")
 @given(everythings(allow_inf=False))
 def test_msgspec_json_unstruct_collection_overrides(everything: Everything):
     """Ensure collection overrides work."""
@@ -776,6 +778,7 @@ def test_msgspec_json_unstruct_collection_overrides(everything: Everything):
     assert raw["a_frozenset"] == sorted(raw["a_frozenset"])
 
 
+@pytest.mark.skipif(python_implementation() == "PyPy", reason="no msgspec on PyPy")
 @given(
     union_and_val=native_unions(
         include_datetimes=False,
diff --git a/tox.ini b/tox.ini
index 6fc0b87a..58f31167 100644
--- a/tox.ini
+++ b/tox.ini
@@ -6,10 +6,10 @@ python =
     3.10: py310
     3.11: py311
     3.12: py312, lint
-    pypy-3: pypy3
+    pypy-3: pypy38
 
 [tox]
-envlist = pypy3, py38, py39, py310, py311, py312, lint
+envlist = pypy38, py38, py39, py310, py311, py312, lint
 isolated_build = true
 skipsdist = true
 
@@ -42,19 +42,14 @@ setenv =
     COVERAGE_PROCESS_START={toxinidir}/pyproject.toml
     COVERAGE_CORE=sysmon
 
-[testenv:pypy3]
+[testenv:pypy38]
 setenv =
-    PYTHONPATH = {toxinidir}:{toxinidir}/cattr
     FAST = 1
-allowlist_externals = pdm
+    PDM_IGNORE_SAVED_PYTHON="1"
+    COVERAGE_PROCESS_START={toxinidir}/pyproject.toml
 commands_pre =
-    pdm sync -G :all,test
+    pdm sync -G ujson,msgpack,pyyaml,tomlkit,cbor2,bson,test
     python -c 'import pathlib; pathlib.Path("{env_site_packages_dir}/cov.pth").write_text("import coverage; coverage.process_startup()")'
-commands =
-    coverage run -m pytest tests {posargs:-n auto}
-passenv = CI
-package = wheel
-wheel_build_env = .pkg
 
 [testenv:docs]
 basepython = python3.11

From 4c9dbd809f2954fa31bce215ca9ec0bccaa2e09c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 02:37:14 +0100
Subject: [PATCH 07/18] Remove unused paramspec

---
 src/cattrs/preconf/msgspec.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 8a4b8f3d..73d7476b 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -3,7 +3,7 @@
 
 from base64 import b64decode
 from datetime import date, datetime
-from typing import Any, ParamSpec, TypeVar, Union
+from typing import Any, TypeVar, Union
 
 from msgspec.json import decode, encode
 
@@ -12,7 +12,6 @@
 from . import wrap
 
 T = TypeVar("T")
-P = ParamSpec("P")
 
 __all__ = ["MsgspecJsonConverter", "configure_converter", "make_converter"]
 

From 7e4fc59873c33c479fb606b5747a94bf3fcd19de Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 13:26:54 +0100
Subject: [PATCH 08/18] Use msgspec's datetime structurer

---
 src/cattrs/preconf/msgspec.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 73d7476b..5ab852ef 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -5,6 +5,7 @@
 from datetime import date, datetime
 from typing import Any, TypeVar, Union
 
+from msgspec import convert
 from msgspec.json import decode, encode
 
 from ..converters import BaseConverter, Converter
@@ -34,7 +35,7 @@ def configure_converter(converter: BaseConverter) -> None:
     * union passthrough configured for str, bool, int, float and None
     """
     converter.register_structure_hook(bytes, lambda v, _: b64decode(v))
-    converter.register_structure_hook(datetime, lambda v, _: datetime.fromisoformat(v))
+    converter.register_structure_hook(datetime, lambda v, _: convert(v, datetime))
     converter.register_structure_hook(date, lambda v, _: date.fromisoformat(v))
     configure_union_passthrough(Union[str, bool, int, float, None], converter)
 

From 3255c268ce7811b3b812f976351133b9071ccb92 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 23:26:08 +0100
Subject: [PATCH 09/18] More msgspec

---
 docs/preconf.md               |  8 +++-
 src/cattrs/preconf/msgspec.py | 85 +++++++++++++++++++++++++++++++++--
 tests/preconf/__init__.py     |  0
 tests/preconf/test_msgspec.py | 80 +++++++++++++++++++++++++++++++++
 tests/typed.py                | 42 ++++++++++++-----
 5 files changed, 200 insertions(+), 15 deletions(-)
 create mode 100644 tests/preconf/__init__.py
 create mode 100644 tests/preconf/test_msgspec.py

diff --git a/docs/preconf.md b/docs/preconf.md
index 257243d1..dc749c49 100644
--- a/docs/preconf.md
+++ b/docs/preconf.md
@@ -77,10 +77,16 @@ _orjson_ only supports mappings with string keys so mappings will have their key
 Found at {mod}`cattrs.preconf.msgspec`.
 Only JSON functionality is currently available, other formats supported by msgspec to follow in the future.
 
+[_msgspec_ structs](https://jcristharif.com/msgspec/structs.html) are supported, but not composable - a struct will be handed over to _msgspec_ directly, and _msgspec_ will handle it.
+_cattrs_ may get more sophisticated handling of structs in the future.
+
 Bytes are un/structured as base 64 strings directly by msgspec.
 _msgspec_ [encodes special float values](https://jcristharif.com/msgspec/supported-types.html#float) (`NaN, Inf, -Inf`) as `null`.
 `datetime` s and `date` s are passed through to be unstructured into RFC 3339 by _msgspec_ itself.
 
+_attrs_ classes, dataclasses and sequences are handled directly by msgspec if possible, otherwise by the normal _cattrs_ machinery.
+This means it's possible the validation errors produced may be _msgspec_ validation errors instead of _cattrs_ validation errors.
+
 _msgspec_ doesn't support PyPy.
 
 ## _ujson_
@@ -89,7 +95,7 @@ Found at {mod}`cattrs.preconf.ujson`.
 
 Bytes are serialized as base 85 strings. Sets are serialized as lists, and deserialized back into sets. `datetime` s and `date` s are serialized as ISO 8601 strings.
 
-`ujson` doesn't support integers less than -9223372036854775808, and greater than 9223372036854775807, nor does it support `float('inf')`.
+_ujson_ doesn't support integers less than -9223372036854775808, and greater than 9223372036854775807, nor does it support `float('inf')`.
 
 
 ## _msgpack_
diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 5ab852ef..08213fa5 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -3,12 +3,18 @@
 
 from base64 import b64decode
 from datetime import date, datetime
-from typing import Any, TypeVar, Union
+from typing import Any, Callable, TypeVar, Union
 
-from msgspec import convert
+from attrs import has as attrs_has
+from attrs import resolve_types
+from msgspec import Struct, convert, to_builtins
 from msgspec.json import decode, encode
 
-from ..converters import BaseConverter, Converter
+from cattrs._compat import fields, get_origin, has, is_bare, is_sequence
+from cattrs.dispatch import HookFactory, UnstructureHook
+from cattrs.fns import identity
+
+from ..converters import Converter
 from ..strategies import configure_union_passthrough
 from . import wrap
 
@@ -22,18 +28,31 @@ def dumps(self, obj: Any, unstructure_as: Any = None, **kwargs: Any) -> bytes:
         """Unstructure and encode `obj` into JSON bytes."""
         return encode(self.unstructure(obj, unstructure_as=unstructure_as), **kwargs)
 
+    def get_dumps_hook(
+        self, unstructure_as: Any, **kwargs: Any
+    ) -> Callable[[Any], bytes]:
+        unstruct_hook = self.get_unstructure_hook(unstructure_as)
+        if unstruct_hook in (identity, to_builtins):
+            return encode
+        return self.dumps
+
     def loads(self, data: bytes, cl: type[T], **kwargs: Any) -> T:
         """Decode and structure `cl` from the provided JSON bytes."""
         return self.structure(decode(data, **kwargs), cl)
 
 
-def configure_converter(converter: BaseConverter) -> None:
+def configure_converter(converter: Converter) -> None:
     """Configure the converter for the msgspec library.
 
     * bytes are serialized as base64 strings, directly by msgspec
     * datetimes and dates are passed through to be serialized as RFC 3339 directly
     * union passthrough configured for str, bool, int, float and None
     """
+    configure_passthroughs(converter)
+
+    converter.register_unstructure_hook(Struct, to_builtins)
+
+    converter.register_structure_hook(Struct, convert)
     converter.register_structure_hook(bytes, lambda v, _: b64decode(v))
     converter.register_structure_hook(datetime, lambda v, _: convert(v, datetime))
     converter.register_structure_hook(date, lambda v, _: date.fromisoformat(v))
@@ -45,3 +64,61 @@ def make_converter(*args: Any, **kwargs: Any) -> MsgspecJsonConverter:
     res = MsgspecJsonConverter(*args, **kwargs)
     configure_converter(res)
     return res
+
+
+def configure_passthroughs(converter: Converter) -> None:
+    """Configure optimizing passthroughs.
+
+    A passthrough is when we let msgspec handle something automatically.
+    """
+    converter.register_unstructure_hook(bytes, to_builtins)
+    converter.register_unstructure_hook_factory(
+        is_sequence, make_unstructure_seq_factory(converter)
+    )
+    converter.register_unstructure_hook_factory(
+        has, make_attrs_unstruct_factory(converter)
+    )
+
+
+def make_unstructure_seq_factory(converter: Converter) -> HookFactory[UnstructureHook]:
+    def unstructure_seq_factory(type) -> UnstructureHook:
+        if is_bare(type):
+            type_arg = Any
+            handler = converter.get_unstructure_hook(type_arg, cache_result=False)
+        elif getattr(type, "__args__", None) not in (None, ()):
+            type_arg = type.__args__[0]
+            handler = converter.get_unstructure_hook(type_arg, cache_result=False)
+        else:
+            handler = None
+
+        if handler in (identity, to_builtins):
+            return handler
+        return converter.gen_unstructure_iterable(type)
+
+    return unstructure_seq_factory
+
+
+def make_attrs_unstruct_factory(converter: Converter) -> HookFactory[UnstructureHook]:
+    """Short-circuit attrs and dataclass handling if it matches msgspec."""
+
+    def attrs_factory(type: Any) -> UnstructureHook:
+        """Choose whether to use msgspec handling or our own."""
+        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(
+            attr.name.startswith("_")
+            or (
+                converter.get_unstructure_hook(attr.type, cache_result=False)
+                not in (identity, to_builtins)
+            )
+            for attr in attribs
+        ):
+            return converter.gen_unstructure_attrs_fromdict(type)
+
+        return to_builtins
+
+    return attrs_factory
diff --git a/tests/preconf/__init__.py b/tests/preconf/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/preconf/test_msgspec.py b/tests/preconf/test_msgspec.py
new file mode 100644
index 00000000..0e31a1e0
--- /dev/null
+++ b/tests/preconf/test_msgspec.py
@@ -0,0 +1,80 @@
+"""Tests for msgspec functionality."""
+from typing import Callable, List
+
+from attrs import define
+from hypothesis import given
+from msgspec import Struct, to_builtins
+from msgspec.json import encode
+from pytest import fixture
+
+from cattrs.fns import identity
+from cattrs.preconf.json import make_converter as make_json_converter
+from cattrs.preconf.msgspec import MsgspecJsonConverter as Conv
+from cattrs.preconf.msgspec import make_converter
+
+from ..typed import simple_typed_classes
+
+
+@define
+class A:
+    a: int
+
+
+@fixture
+def converter() -> Conv:
+    return make_converter()
+
+
+def is_passthrough(fn: Callable) -> bool:
+    return fn in (identity, to_builtins)
+
+
+def test_unstructure_passthrough(converter: Conv):
+    """Passthrough for simple types works."""
+    assert converter.get_unstructure_hook(int) == identity
+    assert converter.get_unstructure_hook(float) == identity
+    assert converter.get_unstructure_hook(str) == identity
+    assert is_passthrough(converter.get_unstructure_hook(bytes))
+    assert converter.get_unstructure_hook(None) == identity
+
+    # Any is special-cased, and we cannot know if it'll match
+    # the msgspec behavior.
+    assert not is_passthrough(converter.get_unstructure_hook(List))
+
+    assert is_passthrough(converter.get_unstructure_hook(List[int]))
+
+
+def test_unstructure_pt_attrs(converter: Conv):
+    """Passthrough for attrs works."""
+    assert is_passthrough(converter.get_unstructure_hook(A))
+
+
+def test_dump_hook_attrs(converter: Conv):
+    """Passthrough for dump hooks works."""
+    assert converter.get_dumps_hook(A) == encode
+
+
+def test_basic_structs(converter: Conv):
+    """Handling msgspec structs works."""
+
+    class B(Struct):
+        b: int
+
+    assert converter.unstructure(B(1)) == {"b": 1}
+
+    assert converter.structure({"b": 1}, B) == B(1)
+
+
+@given(simple_typed_classes(text_codec="ascii", allow_infinity=False, allow_nan=False))
+def test_simple_classes(cls_and_vals):
+    cl, posargs, kwargs = cls_and_vals
+
+    msgspec = make_converter()
+    json = make_json_converter()
+
+    inst = cl(*posargs, **kwargs)
+
+    rebuilt_msgspec = msgspec.loads(msgspec.dumps(inst), cl)
+    rebuilt_json = json.loads(json.dumps(inst), cl)
+
+    assert rebuilt_msgspec == rebuilt_json
diff --git a/tests/typed.py b/tests/typed.py
index 98a2ba82..e3c79f7a 100644
--- a/tests/typed.py
+++ b/tests/typed.py
@@ -33,6 +33,7 @@
     DrawFn,
     SearchStrategy,
     booleans,
+    characters,
     composite,
     dictionaries,
     fixed_dictionaries,
@@ -58,7 +59,14 @@
 
 
 def simple_typed_classes(
-    defaults=None, min_attrs=0, frozen=False, kw_only=None, newtypes=True
+    defaults=None,
+    min_attrs=0,
+    frozen=False,
+    kw_only=None,
+    newtypes=True,
+    text_codec: str = "utf8",
+    allow_infinity=None,
+    allow_nan=None,
 ) -> SearchStrategy[Tuple[Type, PosArgs, KwArgs]]:
     """Yield tuples of (class, values)."""
     return lists_of_typed_attrs(
@@ -67,6 +75,9 @@ def simple_typed_classes(
         for_frozen=frozen,
         kw_only=kw_only,
         newtypes=newtypes,
+        text_codec=text_codec,
+        allow_infinity=allow_infinity,
+        allow_nan=allow_nan,
     ).flatmap(partial(_create_hyp_class, frozen=frozen))
 
 
@@ -97,6 +108,9 @@ def lists_of_typed_attrs(
     allow_mutable_defaults=True,
     kw_only=None,
     newtypes=True,
+    text_codec="utf8",
+    allow_infinity=None,
+    allow_nan=None,
 ) -> SearchStrategy[List[Tuple[_CountingAttr, SearchStrategy[PosArg]]]]:
     # Python functions support up to 255 arguments.
     return lists(
@@ -106,6 +120,9 @@ def lists_of_typed_attrs(
             allow_mutable_defaults=allow_mutable_defaults,
             kw_only=kw_only,
             newtypes=newtypes,
+            text_codec=text_codec,
+            allow_infinity=allow_infinity,
+            allow_nan=allow_nan,
         ),
         min_size=min_size,
         max_size=50,
@@ -122,13 +139,16 @@ def simple_typed_attrs(
     allow_mutable_defaults=True,
     kw_only=None,
     newtypes=True,
+    text_codec="utf8",
+    allow_infinity=None,
+    allow_nan=None,
 ) -> SearchStrategy[Tuple[_CountingAttr, SearchStrategy[PosArgs]]]:
     if not is_39_or_later:
         res = (
             any_typed_attrs(defaults, kw_only)
             | int_typed_attrs(defaults, kw_only)
-            | str_typed_attrs(defaults, kw_only)
-            | float_typed_attrs(defaults, kw_only)
+            | str_typed_attrs(defaults, kw_only, text_codec)
+            | float_typed_attrs(defaults, kw_only, allow_infinity, allow_nan)
             | frozenset_typed_attrs(defaults, legacy_types_only=True, kw_only=kw_only)
             | homo_tuple_typed_attrs(defaults, legacy_types_only=True, kw_only=kw_only)
             | path_typed_attrs(defaults, kw_only=kw_only)
@@ -172,8 +192,8 @@ def simple_typed_attrs(
         res = (
             any_typed_attrs(defaults, kw_only)
             | int_typed_attrs(defaults, kw_only)
-            | str_typed_attrs(defaults, kw_only)
-            | float_typed_attrs(defaults, kw_only)
+            | str_typed_attrs(defaults, kw_only, text_codec)
+            | float_typed_attrs(defaults, kw_only, allow_infinity, allow_nan)
             | frozenset_typed_attrs(defaults, kw_only=kw_only)
             | homo_tuple_typed_attrs(defaults, kw_only=kw_only)
             | path_typed_attrs(defaults, kw_only=kw_only)
@@ -353,7 +373,7 @@ def int_typed_attrs(draw, defaults=None, kw_only=None):
 
 
 @composite
-def str_typed_attrs(draw, defaults=None, kw_only=None):
+def str_typed_attrs(draw, defaults=None, kw_only=None, codec: str = "utf8"):
     """
     Generate a tuple of an attribute and a strategy that yields strs for that
     attribute.
@@ -367,26 +387,28 @@ def str_typed_attrs(draw, defaults=None, kw_only=None):
             default=default,
             kw_only=draw(booleans()) if kw_only is None else kw_only,
         ),
-        text(),
+        text(characters(codec=codec)),
     )
 
 
 @composite
-def float_typed_attrs(draw, defaults=None, kw_only=None):
+def float_typed_attrs(
+    draw, defaults=None, kw_only=None, allow_infinity=None, allow_nan=None
+):
     """
     Generate a tuple of an attribute and a strategy that yields floats for that
     attribute.
     """
     default = NOTHING
     if defaults is True or (defaults is None and draw(booleans())):
-        default = draw(floats())
+        default = draw(floats(allow_infinity=allow_infinity, allow_nan=allow_nan))
     return (
         field(
             type=float,
             default=default,
             kw_only=draw(booleans()) if kw_only is None else kw_only,
         ),
-        floats(),
+        floats(allow_infinity=allow_infinity, allow_nan=allow_nan),
     )
 
 

From 42ab02a36ff8dacb96ac1f70e84162b84d80b36a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Sun, 7 Jan 2024 23:34:36 +0100
Subject: [PATCH 10/18] Ignore _cpython tests on PyPy

---
 src/cattrs/gen/__init__.py                                 | 3 ---
 tests/conftest.py                                          | 3 +++
 tests/preconf/{test_msgspec.py => test_msgspec_cpython.py} | 0
 3 files changed, 3 insertions(+), 3 deletions(-)
 rename tests/preconf/{test_msgspec.py => test_msgspec_cpython.py} (100%)

diff --git a/src/cattrs/gen/__init__.py b/src/cattrs/gen/__init__.py
index 02a676d7..f60ab142 100644
--- a/src/cattrs/gen/__init__.py
+++ b/src/cattrs/gen/__init__.py
@@ -293,9 +293,6 @@ def make_dict_structure_fn(
             mapping = generate_mapping(base, mapping)
             break
 
-    if isinstance(cl, TypeVar):
-        cl = mapping.get(cl.__name__, cl)
-
     cl_name = cl.__name__
     fn_name = "structure_" + cl_name
 
diff --git a/tests/conftest.py b/tests/conftest.py
index 98b74330..d295990e 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,3 +1,4 @@
+import platform
 import sys
 from os import environ
 
@@ -34,3 +35,5 @@ def converter_cls(request):
     collect_ignore_glob.append("*_604.py")
 if sys.version_info < (3, 12):
     collect_ignore_glob.append("*_695.py")
+if platform.python_implementation() == "PyPy":
+    collect_ignore_glob.append("*_cpython.py")
diff --git a/tests/preconf/test_msgspec.py b/tests/preconf/test_msgspec_cpython.py
similarity index 100%
rename from tests/preconf/test_msgspec.py
rename to tests/preconf/test_msgspec_cpython.py

From a8a6027aa2bbc802eedd1efdd62b22cb75413853 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Mon, 8 Jan 2024 00:18:15 +0100
Subject: [PATCH 11/18] More msgspec

---
 src/cattrs/preconf/msgspec.py         | 11 ++++++++---
 tests/preconf/test_msgspec_cpython.py |  2 +-
 tests/test_typeddicts.py              |  6 ++++--
 tests/typeddicts.py                   |  6 ++++--
 4 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 08213fa5..7edd7e1a 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -8,7 +8,7 @@
 from attrs import has as attrs_has
 from attrs import resolve_types
 from msgspec import Struct, convert, to_builtins
-from msgspec.json import decode, encode
+from msgspec.json import Encoder, decode
 
 from cattrs._compat import fields, get_origin, has, is_bare, is_sequence
 from cattrs.dispatch import HookFactory, UnstructureHook
@@ -24,16 +24,21 @@
 
 
 class MsgspecJsonConverter(Converter):
+    _encoder: Encoder = Encoder()
+
     def dumps(self, obj: Any, unstructure_as: Any = None, **kwargs: Any) -> bytes:
         """Unstructure and encode `obj` into JSON bytes."""
-        return encode(self.unstructure(obj, unstructure_as=unstructure_as), **kwargs)
+        return self._encoder.encode(
+            self.unstructure(obj, unstructure_as=unstructure_as), **kwargs
+        )
 
     def get_dumps_hook(
         self, unstructure_as: Any, **kwargs: Any
     ) -> Callable[[Any], bytes]:
+        """Produce a `dumps` hook for the given type."""
         unstruct_hook = self.get_unstructure_hook(unstructure_as)
         if unstruct_hook in (identity, to_builtins):
-            return encode
+            return self._encoder.encode
         return self.dumps
 
     def loads(self, data: bytes, cl: type[T], **kwargs: Any) -> T:
diff --git a/tests/preconf/test_msgspec_cpython.py b/tests/preconf/test_msgspec_cpython.py
index 0e31a1e0..f4b23e2d 100644
--- a/tests/preconf/test_msgspec_cpython.py
+++ b/tests/preconf/test_msgspec_cpython.py
@@ -51,7 +51,7 @@ def test_unstructure_pt_attrs(converter: Conv):
 
 def test_dump_hook_attrs(converter: Conv):
     """Passthrough for dump hooks works."""
-    assert converter.get_dumps_hook(A) == encode
+    assert converter.get_dumps_hook(A) == converter._encoder.encode
 
 
 def test_basic_structs(converter: Conv):
diff --git a/tests/test_typeddicts.py b/tests/test_typeddicts.py
index 1ffa455c..1ec10d91 100644
--- a/tests/test_typeddicts.py
+++ b/tests/test_typeddicts.py
@@ -1,5 +1,5 @@
 """Tests for TypedDict un/structuring."""
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Dict, Generic, Set, Tuple, TypedDict, TypeVar
 
 import pytest
@@ -35,7 +35,9 @@ def mk_converter(detailed_validation: bool = True) -> Converter:
     """We can't use function-scoped fixtures with Hypothesis strats."""
     c = Converter(detailed_validation=detailed_validation)
     c.register_unstructure_hook(datetime, lambda d: d.timestamp())
-    c.register_structure_hook(datetime, lambda d, _: datetime.fromtimestamp(d))
+    c.register_structure_hook(
+        datetime, lambda d, _: datetime.fromtimestamp(d, tz=timezone.utc)
+    )
     return c
 
 
diff --git a/tests/typeddicts.py b/tests/typeddicts.py
index 18453d70..e89dd84d 100644
--- a/tests/typeddicts.py
+++ b/tests/typeddicts.py
@@ -1,5 +1,5 @@
 """Strategies for typed dicts."""
-from datetime import datetime
+from datetime import datetime, timezone
 from string import ascii_lowercase
 from typing import Any, Dict, Generic, List, Optional, Set, Tuple, TypeVar
 
@@ -94,7 +94,9 @@ def datetime_attributes(
     draw: DrawFn, total: bool = True, not_required: bool = False
 ) -> Tuple[datetime, SearchStrategy, SearchStrategy]:
     success_strat = datetimes(
-        min_value=datetime(1970, 1, 1), max_value=datetime(2038, 1, 1)
+        min_value=datetime(1970, 1, 1),
+        max_value=datetime(2038, 1, 1),
+        timezones=just(timezone.utc),
     ).map(lambda dt: dt.replace(microsecond=0))
     type = datetime
     strat = success_strat if total else success_strat | just(NOTHING)

From c67a08796252e97a617a378e536a80a606d7f706 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Mon, 8 Jan 2024 00:53:37 +0100
Subject: [PATCH 12/18] More doc work

---
 docs/_static/custom.css               |  4 ++--
 docs/customizing.md                   |  2 +-
 docs/index.md                         | 20 ++++++++++++++++-
 docs/preconf.md                       | 31 ++++++++++++++++-----------
 src/cattrs/preconf/msgspec.py         |  3 ++-
 tests/preconf/test_msgspec_cpython.py |  1 -
 6 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/docs/_static/custom.css b/docs/_static/custom.css
index f07517a1..de22ab4f 100644
--- a/docs/_static/custom.css
+++ b/docs/_static/custom.css
@@ -72,7 +72,7 @@ span:target ~ h6:first-of-type {
 
 div.article-container > article {
   font-size: 17px;
-  line-height: 31px;
+  line-height: 29px;
 }
 
 div.admonition {
@@ -89,7 +89,7 @@ p.admonition-title {
 
 article > li > a {
   font-size: 19px;
-  line-height: 31px;
+  line-height: 29px;
 }
 
 div.tab-set {
diff --git a/docs/customizing.md b/docs/customizing.md
index 7efc229b..e10a9743 100644
--- a/docs/customizing.md
+++ b/docs/customizing.md
@@ -2,7 +2,7 @@
 
 This section describes customizing the unstructuring and structuring processes in _cattrs_.
 
-## Manual Un/structuring Hooks
+## Custom Un/structuring Hooks
 
 You can write your own structuring and unstructuring functions and register them for types using {meth}`Converter.register_structure_hook() <cattrs.BaseConverter.register_structure_hook>` and {meth}`Converter.register_unstructure_hook() <cattrs.BaseConverter.register_unstructure_hook>`.
 This approach is the most flexible but also requires the most amount of boilerplate.
diff --git a/docs/index.md b/docs/index.md
index 7e7eb8a3..426b60f7 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -2,11 +2,21 @@
 ---
 maxdepth: 2
 hidden: true
+caption: Introduction
 ---
 
 self
 basics
 defaulthooks
+```
+
+```{toctree}
+---
+maxdepth: 2
+hidden: true
+caption: User Guide
+---
+
 customizing
 strategies
 validation
@@ -14,10 +24,18 @@ preconf
 unions
 usage
 indepth
+```
+
+```{toctree}
+---
+maxdepth: 2
+hidden: true
+caption: Dev Guide
+---
+
 history
 benchmarking
 contributing
-API <modules>
 ```
 
 ```{include} ../README.md
diff --git a/docs/preconf.md b/docs/preconf.md
index dc749c49..a3b9bc67 100644
--- a/docs/preconf.md
+++ b/docs/preconf.md
@@ -70,25 +70,31 @@ _orjson_ only supports mappings with string keys so mappings will have their key
 
 ## _msgspec_
 
-```{versionadded} 24.1.0
-
-```
-
 Found at {mod}`cattrs.preconf.msgspec`.
 Only JSON functionality is currently available, other formats supported by msgspec to follow in the future.
 
-[_msgspec_ structs](https://jcristharif.com/msgspec/structs.html) are supported, but not composable - a struct will be handed over to _msgspec_ directly, and _msgspec_ will handle it.
+[_msgspec_ structs](https://jcristharif.com/msgspec/structs.html) are supported, but not composable - a struct will be handed over to _msgspec_ directly, and _msgspec_ will handle and all of its fields, recursively.
 _cattrs_ may get more sophisticated handling of structs in the future.
 
-Bytes are un/structured as base 64 strings directly by msgspec.
-_msgspec_ [encodes special float values](https://jcristharif.com/msgspec/supported-types.html#float) (`NaN, Inf, -Inf`) as `null`.
-`datetime` s and `date` s are passed through to be unstructured into RFC 3339 by _msgspec_ itself.
+[_msgspec_ strict mode](https://jcristharif.com/msgspec/usage.html#strict-vs-lax-mode) is used by default.
+This can be customized by changing the {meth}`encoder <cattrs.preconf.msgspec.MsgspecJsonConverter.encoder>` attribute on the converter.
 
-_attrs_ classes, dataclasses and sequences are handled directly by msgspec if possible, otherwise by the normal _cattrs_ machinery.
+What _cattrs_ calls _unstructuring_ and _structuring_, _msgspec_ calls [`to_builtins` and `convert`](https://jcristharif.com/msgspec/converters.html).
+What _cattrs_ refers to as _dumping_ and _loading_, _msgspec_ refers to as [`encoding` and `decoding`](https://jcristharif.com/msgspec/usage.html).
+
+Compatibility notes:
+- Bytes are un/structured as base 64 strings directly by _msgspec_ itself.
+- _msgspec_ [encodes special float values](https://jcristharif.com/msgspec/supported-types.html#float) (`NaN, Inf, -Inf`) as `null`.
+- `datetime` s and `date` s are passed through to be unstructured into RFC 3339 by _msgspec_ itself.
+- _attrs_ classes, dataclasses and sequences are handled directly by _msgspec_ if possible, otherwise by the normal _cattrs_ machinery.
 This means it's possible the validation errors produced may be _msgspec_ validation errors instead of _cattrs_ validation errors.
 
 _msgspec_ doesn't support PyPy.
 
+```{versionadded} 24.1.0
+
+```
+
 ## _ujson_
 
 Found at {mod}`cattrs.preconf.ujson`.
@@ -111,10 +117,6 @@ When parsing msgpack data from bytes, the library needs to be passed `strict_map
 
 ## _cbor2_
 
-```{versionadded} 23.1.0
-
-```
-
 Found at {mod}`cattrs.preconf.cbor2`.
 
 _cbor2_ implements a fully featured CBOR encoder with several extensions for handling shared references, big integers, rational numbers and so on.
@@ -133,6 +135,9 @@ Use keyword argument `canonical=True` for efficient encoding to the smallest bin
 Floats can be forced to smaller output by casting to lower-precision formats by casting to `numpy` floats (and back to Python floats).
 Example: `float(np.float32(value))` or `float(np.float16(value))`
 
+```{versionadded} 23.1.0
+
+```
 
 ## _bson_
 
diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 7edd7e1a..d85f0c31 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -24,7 +24,8 @@
 
 
 class MsgspecJsonConverter(Converter):
-    _encoder: Encoder = Encoder()
+    #: The msgspec encoder for dumping.
+    encoder: Encoder = Encoder()
 
     def dumps(self, obj: Any, unstructure_as: Any = None, **kwargs: Any) -> bytes:
         """Unstructure and encode `obj` into JSON bytes."""
diff --git a/tests/preconf/test_msgspec_cpython.py b/tests/preconf/test_msgspec_cpython.py
index f4b23e2d..f03100d4 100644
--- a/tests/preconf/test_msgspec_cpython.py
+++ b/tests/preconf/test_msgspec_cpython.py
@@ -4,7 +4,6 @@
 from attrs import define
 from hypothesis import given
 from msgspec import Struct, to_builtins
-from msgspec.json import encode
 from pytest import fixture
 
 from cattrs.fns import identity

From 3aca70832bc45264ee7f7c787d81f806513e6444 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Mon, 8 Jan 2024 02:33:31 +0100
Subject: [PATCH 13/18] Fix

---
 src/cattrs/preconf/msgspec.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index d85f0c31..364b73be 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -29,7 +29,7 @@ class MsgspecJsonConverter(Converter):
 
     def dumps(self, obj: Any, unstructure_as: Any = None, **kwargs: Any) -> bytes:
         """Unstructure and encode `obj` into JSON bytes."""
-        return self._encoder.encode(
+        return self.encoder.encode(
             self.unstructure(obj, unstructure_as=unstructure_as), **kwargs
         )
 
@@ -39,7 +39,7 @@ def get_dumps_hook(
         """Produce a `dumps` hook for the given type."""
         unstruct_hook = self.get_unstructure_hook(unstructure_as)
         if unstruct_hook in (identity, to_builtins):
-            return self._encoder.encode
+            return self.encoder.encode
         return self.dumps
 
     def loads(self, data: bytes, cl: type[T], **kwargs: Any) -> T:

From ec69ae8d2b7cb08a37e15e893d572a4f87919ae6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Mon, 8 Jan 2024 02:38:02 +0100
Subject: [PATCH 14/18] Docs

---
 docs/preconf.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/docs/preconf.md b/docs/preconf.md
index a3b9bc67..4abe7352 100644
--- a/docs/preconf.md
+++ b/docs/preconf.md
@@ -44,6 +44,9 @@ Optional install targets should match the name of the {mod}`cattrs.preconf` modu
 # Using pip
 $ pip install cattrs[ujson]
 
+# Using pdm
+$ pdm add cattrs[orjson]
+
 # Using poetry
 $ poetry add --extras tomlkit cattrs
 ```

From 2333e72eeae35336a413d7e3d8ab281c3970804d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Mon, 8 Jan 2024 10:02:52 +0100
Subject: [PATCH 15/18] Fix test

---
 tests/preconf/test_msgspec_cpython.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/preconf/test_msgspec_cpython.py b/tests/preconf/test_msgspec_cpython.py
index f03100d4..aaa59cc6 100644
--- a/tests/preconf/test_msgspec_cpython.py
+++ b/tests/preconf/test_msgspec_cpython.py
@@ -50,7 +50,7 @@ def test_unstructure_pt_attrs(converter: Conv):
 
 def test_dump_hook_attrs(converter: Conv):
     """Passthrough for dump hooks works."""
-    assert converter.get_dumps_hook(A) == converter._encoder.encode
+    assert converter.get_dumps_hook(A) == converter.encoder.encode
 
 
 def test_basic_structs(converter: Conv):

From b8578e243055b6c29c5f3996a39f2389919fed83 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Fri, 12 Jan 2024 00:45:59 +0100
Subject: [PATCH 16/18] More msgspec work

---
 docs/preconf.md                       | 17 +++++++++++++++++
 src/cattrs/preconf/msgspec.py         |  7 +++++++
 tests/preconf/test_msgspec_cpython.py |  6 ++++++
 3 files changed, 30 insertions(+)

diff --git a/docs/preconf.md b/docs/preconf.md
index 4abe7352..a6ce06a3 100644
--- a/docs/preconf.md
+++ b/docs/preconf.md
@@ -92,6 +92,23 @@ Compatibility notes:
 - _attrs_ classes, dataclasses and sequences are handled directly by _msgspec_ if possible, otherwise by the normal _cattrs_ machinery.
 This means it's possible the validation errors produced may be _msgspec_ validation errors instead of _cattrs_ validation errors.
 
+This converter supports {meth}`get_loads_hook() <cattrs.preconf.msgspec.MsgspecJsonConverter.get_loads_hook>` and {meth}`get_dumps_hook() <cattrs.preconf.msgspec.MsgspecJsonConverter.get_loads_hook>`.
+These are factories for dumping and loading functions (as opposed to unstructuring and structuring); the hooks returned by this may be further optimized to offload as much work as possible to _msgspec_.
+
+```python
+>>> from cattrs.preconf.msgspec import make_converter
+
+>>> @define
+... class Test:
+...     a: int
+
+>>> converter = make_converter()
+>>> dumps = converter.get_dumps_hook(A)
+
+>>> dumps(Test(1))  # Will use msgspec directly.
+b'{"a":1}'
+```
+
 _msgspec_ doesn't support PyPy.
 
 ```{versionadded} 24.1.0
diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 364b73be..1dd3edd1 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -3,6 +3,7 @@
 
 from base64 import b64decode
 from datetime import date, datetime
+from functools import partial
 from typing import Any, Callable, TypeVar, Union
 
 from attrs import has as attrs_has
@@ -24,6 +25,8 @@
 
 
 class MsgspecJsonConverter(Converter):
+    """A converter specialized for the _msgspec_ library."""
+
     #: The msgspec encoder for dumping.
     encoder: Encoder = Encoder()
 
@@ -46,6 +49,10 @@ def loads(self, data: bytes, cl: type[T], **kwargs: Any) -> T:
         """Decode and structure `cl` from the provided JSON bytes."""
         return self.structure(decode(data, **kwargs), cl)
 
+    def get_loads_hook(self, cl: type[T]) -> Callable[[bytes], T]:
+        """Produce a `loads` hook for the given type."""
+        return partial(self.loads, cl=cl)
+
 
 def configure_converter(converter: Converter) -> None:
     """Configure the converter for the msgspec library.
diff --git a/tests/preconf/test_msgspec_cpython.py b/tests/preconf/test_msgspec_cpython.py
index aaa59cc6..19a9add4 100644
--- a/tests/preconf/test_msgspec_cpython.py
+++ b/tests/preconf/test_msgspec_cpython.py
@@ -53,6 +53,12 @@ def test_dump_hook_attrs(converter: Conv):
     assert converter.get_dumps_hook(A) == converter.encoder.encode
 
 
+def test_get_loads_hook(converter: Conv):
+    """`Converter.get_loads_hook` works."""
+    hook = converter.get_loads_hook(A)
+    assert hook(b'{"a": 1}') == A(1)
+
+
 def test_basic_structs(converter: Conv):
     """Handling msgspec structs works."""
 

From 208b66ffa13f158e4dabfe85b1e15e33a7f7712d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Fri, 12 Jan 2024 01:01:54 +0100
Subject: [PATCH 17/18] Pass through mapping to msgspec

---
 docs/preconf.md                       |  2 ++
 src/cattrs/preconf/msgspec.py         | 36 +++++++++++++++++++++-
 tests/preconf/test_msgspec_cpython.py | 44 +++++++++++++++++++++++++--
 3 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/docs/preconf.md b/docs/preconf.md
index a6ce06a3..95f47aa9 100644
--- a/docs/preconf.md
+++ b/docs/preconf.md
@@ -109,6 +109,8 @@ These are factories for dumping and loading functions (as opposed to unstructuri
 b'{"a":1}'
 ```
 
+Due to its complexity, this converter is currently _provisional_ and may slightly change as the best integration patterns are discovered.
+
 _msgspec_ doesn't support PyPy.
 
 ```{versionadded} 24.1.0
diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 1dd3edd1..1ebafebd 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -11,7 +11,7 @@
 from msgspec import Struct, convert, to_builtins
 from msgspec.json import Encoder, decode
 
-from cattrs._compat import fields, get_origin, has, is_bare, is_sequence
+from cattrs._compat import fields, get_origin, has, is_bare, is_mapping, is_sequence
 from cattrs.dispatch import HookFactory, UnstructureHook
 from cattrs.fns import identity
 
@@ -85,6 +85,9 @@ def configure_passthroughs(converter: Converter) -> None:
     A passthrough is when we let msgspec handle something automatically.
     """
     converter.register_unstructure_hook(bytes, to_builtins)
+    converter.register_unstructure_hook_factory(
+        is_mapping, make_unstructure_mapping_factory(converter)
+    )
     converter.register_unstructure_hook_factory(
         is_sequence, make_unstructure_seq_factory(converter)
     )
@@ -111,6 +114,37 @@ def unstructure_seq_factory(type) -> UnstructureHook:
     return unstructure_seq_factory
 
 
+def make_unstructure_mapping_factory(
+    converter: Converter,
+) -> HookFactory[UnstructureHook]:
+    def unstructure_mapping_factory(type) -> UnstructureHook:
+        if is_bare(type):
+            key_arg = Any
+            value_arg = Any
+            key_handler = converter.get_unstructure_hook(key_arg, cache_result=False)
+            value_handler = converter.get_unstructure_hook(
+                value_arg, cache_result=False
+            )
+        elif getattr(type, "__args__", None) not in (None, ()):
+            key_arg = type.__args__[0]
+            value_arg = type.__args__[1]
+            key_handler = converter.get_unstructure_hook(key_arg, cache_result=False)
+            value_handler = converter.get_unstructure_hook(
+                value_arg, cache_result=False
+            )
+        else:
+            key_handler = value_handler = None
+
+        if key_handler in (identity, to_builtins) and value_handler in (
+            identity,
+            to_builtins,
+        ):
+            return to_builtins
+        return converter.gen_unstructure_iterable(type)
+
+    return unstructure_mapping_factory
+
+
 def make_attrs_unstruct_factory(converter: Converter) -> HookFactory[UnstructureHook]:
     """Short-circuit attrs and dataclass handling if it matches msgspec."""
 
diff --git a/tests/preconf/test_msgspec_cpython.py b/tests/preconf/test_msgspec_cpython.py
index 19a9add4..c4ba29d4 100644
--- a/tests/preconf/test_msgspec_cpython.py
+++ b/tests/preconf/test_msgspec_cpython.py
@@ -1,5 +1,14 @@
 """Tests for msgspec functionality."""
-from typing import Callable, List
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    List,
+    Mapping,
+    MutableMapping,
+    MutableSequence,
+    Sequence,
+)
 
 from attrs import define
 from hypothesis import given
@@ -19,6 +28,20 @@ class A:
     a: int
 
 
+@define
+class B:
+    """This class should not be passed through to msgspec."""
+
+    a: Any
+
+
+@define
+class C:
+    """This class should not be passed through to msgspec."""
+
+    _a: int
+
+
 @fixture
 def converter() -> Conv:
     return make_converter()
@@ -41,16 +64,33 @@ def test_unstructure_passthrough(converter: Conv):
     assert not is_passthrough(converter.get_unstructure_hook(List))
 
     assert is_passthrough(converter.get_unstructure_hook(List[int]))
+    assert is_passthrough(converter.get_unstructure_hook(Sequence[int]))
+    assert is_passthrough(converter.get_unstructure_hook(MutableSequence[int]))
 
 
 def test_unstructure_pt_attrs(converter: Conv):
     """Passthrough for attrs works."""
     assert is_passthrough(converter.get_unstructure_hook(A))
+    assert not is_passthrough(converter.get_unstructure_hook(B))
+    assert not is_passthrough(converter.get_unstructure_hook(C))
+
+
+def test_unstructure_pt_mappings(converter: Conv):
+    """Mapping are passed through for unstructuring."""
+    assert is_passthrough(converter.get_unstructure_hook(Dict[str, str]))
+    assert is_passthrough(converter.get_unstructure_hook(Dict[int, int]))
+
+    assert is_passthrough(converter.get_unstructure_hook(Dict[int, A]))
+    assert not is_passthrough(converter.get_unstructure_hook(Dict[int, B]))
+
+    assert is_passthrough(converter.get_unstructure_hook(Mapping[int, int]))
+    assert is_passthrough(converter.get_unstructure_hook(MutableMapping[int, int]))
 
 
-def test_dump_hook_attrs(converter: Conv):
+def test_dump_hook(converter: Conv):
     """Passthrough for dump hooks works."""
     assert converter.get_dumps_hook(A) == converter.encoder.encode
+    assert converter.get_dumps_hook(Dict[str, str]) == converter.encoder.encode
 
 
 def test_get_loads_hook(converter: Conv):

From a973cae81ae16ce63d98f7ce8690d732b162a21f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tin=20Tvrtkovi=C4=87?= <tinchester@gmail.com>
Date: Fri, 12 Jan 2024 01:18:56 +0100
Subject: [PATCH 18/18] Fix counters

---
 src/cattrs/gen/__init__.py    | 17 ++++++++++-------
 src/cattrs/gen/_shared.py     |  6 +++---
 src/cattrs/preconf/msgspec.py | 21 ++++++++++-----------
 3 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/src/cattrs/gen/__init__.py b/src/cattrs/gen/__init__.py
index f60ab142..f1acb6a4 100644
--- a/src/cattrs/gen/__init__.py
+++ b/src/cattrs/gen/__init__.py
@@ -166,7 +166,9 @@ def make_dict_unstructure_fn(
                             # type of the default to dispatch on.
                             t = a.default.__class__
                         try:
-                            handler = converter._unstructure_func.dispatch(t)
+                            handler = converter.get_unstructure_hook(
+                                t, cache_result=False
+                            )
                         except RecursionError:
                             # There's a circular reference somewhere down the line
                             handler = converter.unstructure
@@ -674,7 +676,7 @@ def make_iterable_unstructure_fn(
         # We don't know how to handle the TypeVar on this level,
         # so we skip doing the dispatch here.
         if not isinstance(type_arg, TypeVar):
-            handler = converter._unstructure_func.dispatch(type_arg)
+            handler = converter.get_unstructure_hook(type_arg, cache_result=False)
 
     globs = {"__cattr_seq_cl": unstructure_to or cl, "__cattr_u": handler}
     lines = []
@@ -703,7 +705,8 @@ def make_hetero_tuple_unstructure_fn(
 
     # We can do the dispatch here and now.
     handlers = [
-        converter._unstructure_func.dispatch(type_arg) for type_arg in type_args
+        converter.get_unstructure_hook(type_arg, cache_result=False)
+        for type_arg in type_args
     ]
 
     globs = {f"__cattr_u_{i}": h for i, h in enumerate(handlers)}
@@ -758,11 +761,11 @@ def make_mapping_unstructure_fn(
             # Probably a Counter
             key_arg, val_arg = args, Any
         # We can do the dispatch here and now.
-        kh = key_handler or converter._unstructure_func.dispatch(key_arg)
+        kh = key_handler or converter.get_unstructure_hook(key_arg, cache_result=False)
         if kh == identity:
             kh = None
 
-        val_handler = converter._unstructure_func.dispatch(val_arg)
+        val_handler = converter.get_unstructure_hook(val_arg, cache_result=False)
         if val_handler == identity:
             val_handler = None
 
@@ -830,11 +833,11 @@ def make_mapping_structure_fn(
         is_bare_dict = val_type is Any and key_type is Any
         if not is_bare_dict:
             # We can do the dispatch here and now.
-            key_handler = converter.get_structure_hook(key_type)
+            key_handler = converter.get_structure_hook(key_type, cache_result=False)
             if key_handler == converter._structure_call:
                 key_handler = key_type
 
-            val_handler = converter.get_structure_hook(val_type)
+            val_handler = converter.get_structure_hook(val_type, cache_result=False)
             if val_handler == converter._structure_call:
                 val_handler = val_type
 
diff --git a/src/cattrs/gen/_shared.py b/src/cattrs/gen/_shared.py
index 2bd1007f..78c2bc09 100644
--- a/src/cattrs/gen/_shared.py
+++ b/src/cattrs/gen/_shared.py
@@ -23,7 +23,7 @@ def find_structure_handler(
         # so it falls back to that.
         handler = None
     elif a.converter is not None and not prefer_attrs_converters and type is not None:
-        handler = c.get_structure_hook(type)
+        handler = c.get_structure_hook(type, cache_result=False)
         if handler == raise_error:
             handler = None
     elif type is not None:
@@ -35,7 +35,7 @@ def find_structure_handler(
             # This is a special case where we can use the
             # type of the default to dispatch on.
             type = a.default.__class__
-            handler = c.get_structure_hook(type)
+            handler = c.get_structure_hook(type, cache_result=False)
             if handler == c._structure_call:
                 # Finals can't really be used with _structure_call, so
                 # we wrap it so the rest of the toolchain doesn't get
@@ -45,7 +45,7 @@ def handler(v, _, _h=handler):
                     return _h(v, type)
 
         else:
-            handler = c.get_structure_hook(type)
+            handler = c.get_structure_hook(type, cache_result=False)
     else:
         handler = c.structure
     return handler
diff --git a/src/cattrs/preconf/msgspec.py b/src/cattrs/preconf/msgspec.py
index 1ebafebd..a9225970 100644
--- a/src/cattrs/preconf/msgspec.py
+++ b/src/cattrs/preconf/msgspec.py
@@ -120,18 +120,17 @@ def make_unstructure_mapping_factory(
     def unstructure_mapping_factory(type) -> UnstructureHook:
         if is_bare(type):
             key_arg = Any
-            value_arg = Any
+            val_arg = Any
             key_handler = converter.get_unstructure_hook(key_arg, cache_result=False)
-            value_handler = converter.get_unstructure_hook(
-                value_arg, cache_result=False
-            )
-        elif getattr(type, "__args__", None) not in (None, ()):
-            key_arg = type.__args__[0]
-            value_arg = type.__args__[1]
+            value_handler = converter.get_unstructure_hook(val_arg, cache_result=False)
+        elif (args := getattr(type, "__args__", None)) not in (None, ()):
+            if len(args) == 2:
+                key_arg, val_arg = args
+            else:
+                # Probably a Counter
+                key_arg, val_arg = args, Any
             key_handler = converter.get_unstructure_hook(key_arg, cache_result=False)
-            value_handler = converter.get_unstructure_hook(
-                value_arg, cache_result=False
-            )
+            value_handler = converter.get_unstructure_hook(val_arg, cache_result=False)
         else:
             key_handler = value_handler = None
 
@@ -140,7 +139,7 @@ def unstructure_mapping_factory(type) -> UnstructureHook:
             to_builtins,
         ):
             return to_builtins
-        return converter.gen_unstructure_iterable(type)
+        return converter.gen_unstructure_mapping(type)
 
     return unstructure_mapping_factory