Merge pull request #75 from KotlinIsland/actually-fix-reified-generic-for-pyright

actual fix for `ReifiedGeneric` with pyright

Author: DetachHead

.github/workflows/check.yaml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11-dev"]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
 
     steps:
       - uses: actions/checkout@v2
@@ -32,7 +32,7 @@ jobs:
         if: steps.cache.outputs.cache-hit == 'true'
         run: timeout 10s poetry run pip --version || rm -rf .venv
       - run: poetry install
-      - run: poetry run mypy -p basedtyping -p tests
+      - run: poetry run mypy -p basedtyping -p tests --python-version ${{ matrix.python-version }}
       - run: poetry run pytest tests/
 
   lint:
@@ -41,7 +41,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v4
         with:
-          python-version: "3.7"
+          python-version: "3.8"
       - name: Run image
         uses: abatilo/[email protected]
         with:

.idea/inspectionProfiles/Project_Default.xml

@@ -18,7 +18,7 @@
     cast,
 )
 
-from typing_extensions import Final, Self, TypeAlias, TypeGuard
+from typing_extensions import Final, TypeAlias, TypeGuard
 
 from basedtyping.runtime_only import OldUnionType
 
@@ -109,7 +109,7 @@ class NotEnoughTypeParametersError(ReifiedGenericError):
     """
 
 
-class _ReifiedGenericMetaclass(type, Generic[T]):
+class _ReifiedGenericMetaclass(type):
     # these should really only be on the class not the metaclass, but since it needs to be accessible from both instances and the class itself, its duplicated here
 
     __reified_generics__: Tuple[type, ...]
@@ -125,7 +125,7 @@ class _ReifiedGenericMetaclass(type, Generic[T]):
     _can_do_instance_and_subclass_checks_without_generics: bool
     """Used internally for ``isinstance`` and ``issubclass`` checks, ``True`` when the class can currenty be used in said checks without generics in them"""
 
-    def _orig_class(cls) -> _ReifiedGenericMetaclass[T]:
+    def _orig_class(cls) -> _ReifiedGenericMetaclass:
         """Gets the original class that ``ReifiedGeneric.__class_getitem__`` copied from
         """
         result = cls.__bases__[0]
@@ -175,7 +175,7 @@ def _check_generics_reified(cls) -> None:
         if not cls._generics_are_reified() or cls._has_non_reified_type_vars():
             cls._raise_generics_not_reified()
 
-    def _is_subclass(cls, subclass: object) -> TypeGuard[_ReifiedGenericMetaclass[T]]:
+    def _is_subclass(cls, subclass: object) -> TypeGuard[_ReifiedGenericMetaclass]:
         """For ``__instancecheck__`` and ``__subclasscheck__``. checks whether the
         "origin" type (ie. without the generics) is a subclass of this reified generic
         """
@@ -188,7 +188,7 @@ def _is_subclass(cls, subclass: object) -> TypeGuard[_ReifiedGenericMetaclass[T]
             cls._orig_class(),
             # https://github.com/python/mypy/issues/11671
             cast(  # pylint:disable=protected-access
-                _ReifiedGenericMetaclass[T], subclass
+                _ReifiedGenericMetaclass, subclass
             )._orig_class(),
         )
 
@@ -220,40 +220,35 @@ def __instancecheck__(cls, instance: object) -> bool:
             cast(ReifiedGeneric[object], instance).__reified_generics__
         )
 
-    def __call__(cls, *args: object, **kwargs: object) -> T:
+    # need the generic here for pyright. see https://github.com/microsoft/pyright/issues/5488
+    def __call__(cls: type[T], *args: object, **kwargs: object) -> T:
         """A placeholder ``__call__`` method that gets called when the class is
         instantiated directly, instead of first supplying the type parameters.
         """
+        cls_narrowed = cast(Type[ReifiedGeneric[object]], cls)
         if (
             # instantiating a ReifiedGeneric without specifying any TypeVars
-            not hasattr(cls, "_orig_type_vars")
+            not hasattr(cls_narrowed, "_orig_type_vars")
             # instantiating a subtype of a ReifiedGeneric without specifying any TypeVars
-            or cls._orig_type_vars == cls.__type_vars__
+            or cls_narrowed._orig_type_vars == cls_narrowed.__type_vars__
         ):
             raise NotReifiedError(
-                f"Cannot instantiate ReifiedGeneric {cls.__name__!r} because its type"
-                " parameters were not supplied. The type parameters must be explicitly"
-                " specified in the instantiation so that the type data can be made"
-                " available at runtime.\n\n"
-                "For example:\n\n"
-                "foo: Foo[int] = Foo()  #wrong\n"
-                "foo = Foo[T]()  #wrong\n"
-                "foo = Foo[int]()  # correct"
+                f"Cannot instantiate ReifiedGeneric {cls_narrowed.__name__!r} because"
+                " its type parameters were not supplied. The type parameters must be"
+                " explicitly specified in the instantiation so that the type data can"
+                " be made available at runtime.\n\nFor example:\n\nfoo: Foo[int] ="
+                " Foo()  #wrong\nfoo = Foo[T]()  #wrong\nfoo = Foo[int]()  # correct"
             )
-        cls._check_generics_reified()
-        return cast(T, super().__call__(*args, **kwargs))
+        cls_narrowed._check_generics_reified()
+        # see comment about cls above
+        return cast(T, super().__call__(*args, **kwargs))  # type:ignore[misc]
 
 
 GenericItems: TypeAlias = Union[type, TypeVar, Tuple[Union[type, TypeVar], ...]]
 """The ``items`` argument passed to ``__class_getitem__`` when creating or using a ``Generic``"""
 
 
-class ReifiedGeneric(
-    Generic[T],
-    # mypy doesn't support metaclasses with generics but for pyright we need to correctly type the `__call__`
-    # return type, otherwise all instances of `ReifiedGeneric` will have the wrong type
-    metaclass=_ReifiedGenericMetaclass[Self],  # type:ignore[misc]
-):
+class ReifiedGeneric(Generic[T], metaclass=_ReifiedGenericMetaclass):
     """A ``Generic`` where the type parameters are available at runtime and is
     usable in ``isinstance`` and ``issubclass`` checks.
 
@@ -316,7 +311,9 @@ def __class_getitem__(  # type: ignore[no-any-decorated]
         orig_type_vars = (
             cls.__type_vars__
             if hasattr(cls, "__type_vars__")
-            else cast(Tuple[TypeVar, ...], cls.__parameters__)
+            else cast(
+                Tuple[TypeVar, ...], cls.__parameters__  # type:ignore[attr-defined]
+            )
         )
 
         # add any reified generics from the superclass if there is one

basedtyping/__init__.py

@@ -23,6 +23,7 @@ build-backend = "poetry.core.masonry.api"
 requires = ["poetry-core>=1.0.8"]
 
 [tool.mypy]
+python_version = 3.8
 pretty = true
 show_error_context = true
 
@@ -32,8 +33,9 @@ multi_line_output = 3
 combine_as_imports = true
 
 [tool.black]
-target-version = ["py37"]
+target-version = ["py38"]
 preview = true
+skip-magic-trailing-comma = true
 
 [tool.pylint.MASTER]
 fail-on = "I"

pyproject.toml

@@ -19,20 +19,13 @@ def test_union_first_arg() -> None:
 
 def test_old_union() -> None:
     # TODO: fix the mypy error
-    assert not issubform(
-        Union[int, str],  # type: ignore[arg-type]
-        int,
-    )
-    assert issubform(
-        Union[int, str],  # type: ignore[arg-type]
-        object,
-    )
+    assert not issubform(Union[int, str], int)  # type: ignore[arg-type]
+    assert issubform(Union[int, str], object)  # type: ignore[arg-type]
     assert issubform(
         Union[int, str],  # type: ignore[arg-type]
         Union[str, int],  # type: ignore[arg-type]
     )
     if sys.version_info >= (3, 10):
         assert issubform(
-            Union[int, str],  # type: ignore[unused-ignore, arg-type]
-            int | str,
+            Union[int, str], int | str  # type: ignore[unused-ignore, arg-type]
         )

tests/test_is_subform.py

@@ -8,8 +8,7 @@
 @mark.xfail  # https://github.com/KotlinIsland/basedtyping/issues/22
 def test_isinstance() -> None:
     assert not isinstance(  # type: ignore[misc]
-        1,
-        Never,  # type: ignore[arg-type]
+        1, Never  # type: ignore[arg-type]
     )
 
 

tests/test_never_type/test_runtime.py

@@ -14,7 +14,8 @@ class Reified(ReifiedGeneric[Tuple[T, T2]]):
     pass
 
 
-class ReifiedList(ReifiedGeneric[Tuple[T]], List[T]):
+# TODO: investigate this "metaclass conflict" mypy error
+class ReifiedList(ReifiedGeneric[Tuple[T]], List[T]):  # type:ignore[misc]
     pass
 
 

tests/test_reified_generics/test_reified_generic.py

@@ -13,7 +13,8 @@ class Reified(ReifiedGeneric[Tuple[T, T2]]):
     pass
 
 
-class ReifiedList(ReifiedGeneric[Tuple[T]], List[T]):
+# TODO: investigate this "metaclass conflict" mypy error
+class ReifiedList(ReifiedGeneric[Tuple[T]], List[T]):  # type:ignore[misc]
     pass