Simulate @deconstructible as a mixin class (#1818)

`@desconstructible` inserts its own `__new__` method and adds a
`deconstruct` method to decorated classes. We can simulate that
behaviour with a class definition, which decorated classes inherits.

django-stubs/contrib/auth/validators.pyi

@@ -1,10 +1,4 @@
-from collections.abc import Sequence
-from typing import Any
-
 from django.core.validators import RegexValidator
 
-class ASCIIUsernameValidator(RegexValidator):
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
-
-class UnicodeUsernameValidator(RegexValidator):
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
+class ASCIIUsernameValidator(RegexValidator): ...
+class UnicodeUsernameValidator(RegexValidator): ...

django-stubs/contrib/gis/geos/geometry.pyi

@@ -1,4 +1,3 @@
-from collections.abc import Sequence
 from typing import Any
 
 from django.contrib.gis.gdal import CoordTransform, SpatialReference
@@ -8,6 +7,7 @@ from django.contrib.gis.geos.coordseq import GEOSCoordSeq
 from django.contrib.gis.geos.mutable_list import ListMixin
 from django.contrib.gis.geos.point import Point
 from django.contrib.gis.geos.prepared import PreparedGeometry
+from django.utils.deconstruct import _Deconstructible
 from typing_extensions import Self
 
 class GEOSGeometryBase(GEOSBase):
@@ -142,6 +142,5 @@ class LinearGeometryMixin:
     @property
     def closed(self) -> bool: ...
 
-class GEOSGeometry(GEOSGeometryBase, ListMixin):
+class GEOSGeometry(_Deconstructible, GEOSGeometryBase, ListMixin):
     def __init__(self, geo_input: Any, srid: int | None = ...) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...

django-stubs/contrib/postgres/validators.pyi

@@ -1,17 +1,17 @@
-from collections.abc import Iterable, Mapping, Sequence
+from collections.abc import Iterable, Mapping
 from typing import Any
 
 from django.core.validators import MaxLengthValidator, MaxValueValidator, MinLengthValidator, MinValueValidator
+from django.utils.deconstruct import _Deconstructible
 
 class ArrayMaxLengthValidator(MaxLengthValidator): ...
 class ArrayMinLengthValidator(MinLengthValidator): ...
 
-class KeysValidator:
+class KeysValidator(_Deconstructible):
     messages: dict[str, str]
     strict: bool
     def __init__(self, keys: Iterable[str], strict: bool = ..., messages: Mapping[str, str] | None = ...) -> None: ...
     def __call__(self, value: Any) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...  # fake
 
 class RangeMaxValueValidator(MaxValueValidator): ...
 class RangeMinValueValidator(MinValueValidator): ...

django-stubs/core/files/storage/filesystem.pyi

@@ -1,13 +1,11 @@
-from collections.abc import Sequence
-from typing import Any
-
 from django.utils._os import _PathCompatible
+from django.utils.deconstruct import _Deconstructible
 from django.utils.functional import cached_property
 
 from .base import Storage
 from .mixins import StorageSettingsMixin
 
-class FileSystemStorage(Storage, StorageSettingsMixin):
+class FileSystemStorage(_Deconstructible, Storage, StorageSettingsMixin):
     OS_OPEN_FLAGS: int
 
     def __init__(
@@ -27,4 +25,3 @@ class FileSystemStorage(Storage, StorageSettingsMixin):
     def file_permissions_mode(self) -> int | None: ...
     @cached_property
     def directory_permissions_mode(self) -> int | None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...  # fake

django-stubs/core/files/storage/memory.pyi

@@ -1,13 +1,11 @@
-from collections.abc import Sequence
-from typing import Any
-
 from django.utils._os import _PathCompatible
+from django.utils.deconstruct import _Deconstructible
 from django.utils.functional import cached_property
 
 from .base import Storage
 from .mixins import StorageSettingsMixin
 
-class InMemoryStorage(Storage, StorageSettingsMixin):
+class InMemoryStorage(_Deconstructible, Storage, StorageSettingsMixin):
     def __init__(
         self,
         location: _PathCompatible | None = ...,
@@ -25,4 +23,3 @@ class InMemoryStorage(Storage, StorageSettingsMixin):
     def file_permissions_mode(self) -> int | None: ...
     @cached_property
     def directory_permissions_mode(self) -> int | None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...  # fake

django-stubs/core/validators.pyi

@@ -4,6 +4,7 @@ from re import Pattern, RegexFlag
 from typing import Any
 
 from django.core.files.base import File
+from django.utils.deconstruct import _Deconstructible
 from django.utils.functional import _StrOrPromise
 from typing_extensions import TypeAlias
 
@@ -13,7 +14,7 @@ _Regex: TypeAlias = str | Pattern[str]
 
 _ValidatorCallable: TypeAlias = Callable[[Any], None]  # noqa: PYI047
 
-class RegexValidator:
+class RegexValidator(_Deconstructible):
     regex: _Regex  # Pattern[str] on instance, but may be str on class definition
     message: _StrOrPromise
     code: str
@@ -28,7 +29,6 @@ class RegexValidator:
         flags: RegexFlag | None = ...,
     ) -> None: ...
     def __call__(self, value: Any) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class URLValidator(RegexValidator):
     ul: str
@@ -43,13 +43,12 @@ class URLValidator(RegexValidator):
     max_length: int
     def __init__(self, schemes: Sequence[str] | None = ..., **kwargs: Any) -> None: ...
     def __call__(self, value: str) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 integer_validator: RegexValidator
 
 def validate_integer(value: float | str | None) -> None: ...
 
-class EmailValidator:
+class EmailValidator(_Deconstructible):
     message: _StrOrPromise
     code: str
     user_regex: Pattern[str]
@@ -65,7 +64,6 @@ class EmailValidator:
     def __call__(self, value: str | None) -> None: ...
     def validate_domain_part(self, domain_part: str) -> bool: ...
     def __eq__(self, other: object) -> bool: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 validate_email: EmailValidator
 slug_re: Pattern[str]
@@ -87,7 +85,7 @@ def int_list_validator(
 
 validate_comma_separated_integer_list: RegexValidator
 
-class BaseValidator:
+class BaseValidator(_Deconstructible):
     message: _StrOrPromise
     code: str
     limit_value: Any
@@ -96,35 +94,26 @@ class BaseValidator:
     def compare(self, a: Any, b: Any) -> bool: ...
     def clean(self, x: Any) -> Any: ...
     def __eq__(self, other: object) -> bool: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
-class MaxValueValidator(BaseValidator):
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
-
-class MinValueValidator(BaseValidator):
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
-
-class StepValueValidator(BaseValidator):
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
+class MaxValueValidator(BaseValidator): ...
+class MinValueValidator(BaseValidator): ...
+class StepValueValidator(BaseValidator): ...
 
 class MinLengthValidator(BaseValidator):
     def clean(self, x: Sized) -> int: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class MaxLengthValidator(BaseValidator):
     def clean(self, x: Sized) -> int: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
-class DecimalValidator:
+class DecimalValidator(_Deconstructible):
     messages: dict[str, str]
     max_digits: int | None
     decimal_places: int | None
     def __init__(self, max_digits: int | None, decimal_places: int | None) -> None: ...
     def __call__(self, value: Decimal) -> None: ...
     def __eq__(self, other: object) -> bool: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
-class FileExtensionValidator:
+class FileExtensionValidator(_Deconstructible):
     message: _StrOrPromise
     code: str
     allowed_extensions: Collection[str] | None
@@ -135,14 +124,12 @@ class FileExtensionValidator:
         code: str | None = ...,
     ) -> None: ...
     def __call__(self, value: File) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 def get_available_image_extensions() -> Sequence[str]: ...
 def validate_image_file_extension(value: File) -> None: ...
 
-class ProhibitNullCharactersValidator:
+class ProhibitNullCharactersValidator(_Deconstructible):
     message: _StrOrPromise
     code: str
     def __init__(self, message: _StrOrPromise | None = ..., code: str | None = ...) -> None: ...
     def __call__(self, value: Any) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...

django-stubs/db/models/expressions.pyi

@@ -10,6 +10,7 @@ from django.db.models.lookups import Lookup, Transform
 from django.db.models.query import QuerySet
 from django.db.models.sql.compiler import SQLCompiler, _AsSqlType
 from django.db.models.sql.query import Query
+from django.utils.deconstruct import _Deconstructible
 from typing_extensions import Self, TypeAlias
 
 class SQLiteNumericMixin:
@@ -108,8 +109,7 @@ class BaseExpression:
     def flatten(self) -> Iterator[BaseExpression]: ...
     def as_sql(self, compiler: SQLCompiler, connection: BaseDatabaseWrapper) -> _AsSqlType: ...
 
-class Expression(BaseExpression, Combinable):
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
+class Expression(_Deconstructible, BaseExpression, Combinable): ...
 
 class CombinedExpression(SQLiteNumericMixin, Expression):
     connector: str
@@ -123,7 +123,7 @@ class DurationExpression(CombinedExpression):
 class TemporalSubtraction(CombinedExpression):
     def __init__(self, lhs: Combinable, rhs: Combinable) -> None: ...
 
-class F(Combinable):
+class F(_Deconstructible, Combinable):
     name: str
     def __init__(self, name: str) -> None: ...
     def resolve_expression(
@@ -149,7 +149,6 @@ class F(Combinable):
         nulls_last: bool | None = ...,
     ) -> OrderBy: ...
     def copy(self) -> F: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class ResolvedOuterRef(F):
     contains_aggregate: ClassVar[bool]
@@ -179,12 +178,10 @@ class Func(SQLiteNumericMixin, Expression):
         arg_joiner: str | None = ...,
         **extra_context: Any,
     ) -> _AsSqlType: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class Value(Expression):
     value: Any
     def __init__(self, value: Any, output_field: Field | None = ...) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class RawSQL(Expression):
     params: list[Any]
@@ -213,7 +210,6 @@ _E = TypeVar("_E", bound=Q | Combinable)
 class ExpressionWrapper(Expression, Generic[_E]):
     def __init__(self, expression: _E, output_field: Field) -> None: ...
     expression: _E
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class NegatedExpression(ExpressionWrapper[_E]):
     def __init__(self, expression: _E) -> None: ...
@@ -224,7 +220,6 @@ class When(Expression):
     condition: Any
     result: Any
     def __init__(self, condition: Any = ..., then: Any = ..., **lookups: Any) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class Case(Expression):
     template: str
@@ -235,7 +230,6 @@ class Case(Expression):
     def __init__(
         self, *cases: Any, default: Any | None = ..., output_field: Field | None = ..., **extra: Any
     ) -> None: ...
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class Subquery(BaseExpression, Combinable):
     template: str
@@ -261,7 +255,6 @@ class OrderBy(Expression):
     ) -> None: ...
     def asc(self) -> None: ...  # type: ignore[override]
     def desc(self) -> None: ...  # type: ignore[override]
-    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
 
 class Window(SQLiteNumericMixin, Expression):
     template: str

django-stubs/utils/deconstruct.pyi

@@ -1,6 +1,13 @@
-from collections.abc import Callable
+from collections.abc import Callable, Sequence
 from typing import Any, TypeVar, overload
 
+from typing_extensions import Self
+
+# Contains additions from a class being decorated with '@deconstructible'
+class _Deconstructible:
+    def __new__(cls, *args: Any, **kwargs: Any) -> Self: ...
+    def deconstruct(obj) -> tuple[str, Sequence[Any], dict[str, Any]]: ...
+
 _T = TypeVar("_T")
 _TCallable = TypeVar("_TCallable", bound=Callable[..., Any])