Use __class_getitem__ instead of metaclass

Author: romis2012

pydantic_collections/_v1.py

@@ -8,7 +8,7 @@
 from pydantic.fields import ModelField, Undefined
 
 # noinspection PyProtectedMember
-from pydantic.main import ModelMetaclass, Extra
+from pydantic.main import Extra
 
 
 class CollectionModelConfig(BaseConfig):
@@ -32,9 +32,22 @@ def inner(*args, **kwargs):
     return inner
 
 
-class BaseCollectionModelMeta(ModelMetaclass):
+TElement = TypeVar('TElement')
+
+
+class BaseCollectionModel(BaseModel, MutableSequence[TElement]):
+    if TYPE_CHECKING:  # pragma: no cover
+        __el_field__: ModelField
+        __config__: Type[CollectionModelConfig]
+        __root__: List[TElement]
+
+    class Config(CollectionModelConfig):
+        extra = Extra.forbid
+        validate_assignment = True
+        validate_assignment_strict = True
+
     @tp_cache
-    def __getitem__(cls: Type['BaseCollectionModel'], el_type):
+    def __class_getitem__(cls, el_type):
         if not issubclass(cls, BaseCollectionModel):
             raise TypeError('{!r} is not a BaseCollectionModel'.format(cls))  # pragma: no cover
 
@@ -54,21 +67,6 @@ def __getitem__(cls: Type['BaseCollectionModel'], el_type):
             },
         )
 
-
-T = TypeVar('T')
-
-
-class BaseCollectionModel(BaseModel, MutableSequence[T], metaclass=BaseCollectionModelMeta):
-    if TYPE_CHECKING:  # pragma: no cover
-        __el_field__: ModelField
-        __config__: Type[CollectionModelConfig]
-        __root__: List[T]
-
-    class Config(CollectionModelConfig):
-        extra = Extra.forbid
-        validate_assignment = True
-        validate_assignment_strict = True
-
     def __init__(self, data: list = None, **kwargs):
         __root__ = kwargs.get('__root__')
         if __root__ is None:
@@ -138,7 +136,7 @@ def __setitem__(self, index, value):
     def __delitem__(self, index):
         del self.__root__[index]
 
-    def __iter__(self) -> List[T]:
+    def __iter__(self) -> List[TElement]:
         yield from self.__root__
 
     def __repr__(self):
@@ -167,7 +165,7 @@ def dict(
         exclude_defaults: bool = False,
         exclude_none: bool = False,
         **kwargs,
-    ) -> List[T]:
+    ) -> List[TElement]:
         data = super().dict(
             by_alias=by_alias,
             skip_defaults=skip_defaults,

pydantic_collections/_v2.py

@@ -1,18 +1,18 @@
-import collections.abc
 import functools
 import types
 from dataclasses import dataclass
 from typing import (
-    Type,
     List,
     TYPE_CHECKING,
     Any,
     Tuple,
     Union,
     Dict,
+    TypeVar,
+    MutableSequence,
 )
 
-from pydantic import BaseModel, RootModel, TypeAdapter, ConfigDict, ValidationError
+from pydantic import RootModel, TypeAdapter, ConfigDict, ValidationError
 from pydantic_core import PydanticUndefined, ErrorDetails
 from typing_extensions import get_origin, get_args
 
@@ -65,9 +65,21 @@ class Element:
     adapter: TypeAdapter
 
 
-class BaseCollectionModelMeta(BaseModel.__class__):
+TElement = TypeVar("TElement")
+
+
+class BaseCollectionModel(MutableSequence[TElement], RootModel[List[TElement]]):
+    if TYPE_CHECKING:  # pragma: no cover
+        __element__: Element
+
+    # noinspection Pydantic
+    model_config = CollectionModelConfig(
+        validate_assignment=True,
+        validate_assignment_strict=True,
+    )
+
     @tp_cache
-    def __getitem__(cls: Type['BaseCollectionModel'], el_type):
+    def __class_getitem__(cls, el_type):
         if not issubclass(cls, BaseCollectionModel):
             raise TypeError('{!r} is not a BaseCollectionModel'.format(cls))  # pragma: no cover
 
@@ -81,20 +93,6 @@ def __getitem__(cls: Type['BaseCollectionModel'], el_type):
             },
         )
 
-
-class BaseCollectionModel(
-    RootModel,
-    collections.abc.MutableSequence,
-    metaclass=BaseCollectionModelMeta,
-):
-    if TYPE_CHECKING:  # pragma: no cover
-        __element__: Element
-
-    model_config = CollectionModelConfig(
-        validate_assignment=True,
-        validate_assignment_strict=True,
-    )
-
     def __init__(self, data: list = None, root=PydanticUndefined, **kwargs):
         if root is PydanticUndefined:
             if data is None:

requirements-dev.txt

@@ -1,5 +1,7 @@
 # pydantic>=1.8.2,<2.0
 typing_extensions>=4.7.1
-flake8==3.9.1
-pytest==7.0.1
-pytest-cov==3.0.0
+flake8>=3.9.1
+pytest==7.0.1; python_version < "3.8"
+pytest-cov==3.0.0; python_version < "3.8"
+pytest==8.0.2; python_version >= "3.8"
+pytest-cov==4.1.0; python_version >= "3.8"