Handle X | Y union in GenericModel (#4977)

* Fix X | Y union syntax breaks GenericModel (#4146)

* Update changes/4146-thenx.md

Co-authored-by: ⬢ Samuel Colvin <s@muelcolvin.com>

* Improve tests

* Recreate newstyle union via typing._UnionGenericAlias

* Add basic pep-604 union args order caching detection test

---------

Co-authored-by: ⬢ Samuel Colvin <s@muelcolvin.com>

changes/4146-thenx.md

@@ -0,0 +1 @@
+Fix `X | Y` union syntax breaking `GenericModel`

pydantic/generics.py

@@ -1,4 +1,5 @@
 import sys
+import types
 import typing
 from typing import (
     TYPE_CHECKING,
@@ -26,6 +27,9 @@
 from .typing import display_as_type, get_all_type_hints, get_args, get_origin, typing_base
 from .utils import LimitedDict, all_identical, lenient_issubclass
 
+if sys.version_info >= (3, 10):
+    from typing import _UnionGenericAlias
+
 GenericModelT = TypeVar('GenericModelT', bound='GenericModel')
 TypeVarType = Any  # since mypy doesn't allow the use of TypeVar as a type
 
@@ -268,6 +272,10 @@ def replace_types(type_: Any, type_map: Mapping[Any, Any]) -> Any:
             # See: https://www.python.org/dev/peps/pep-0585
             origin_type = getattr(typing, type_._name)
         assert origin_type is not None
+        # PEP-604 syntax (Ex.: list | str) is represented with a types.UnionType object that does not have __getitem__.
+        # We also cannot use isinstance() since we have to compare types.
+        if sys.version_info >= (3, 10) and origin_type is types.UnionType:  # noqa: E721
+            return _UnionGenericAlias(origin_type, resolved_type_args)
         return origin_type[resolved_type_args]
 
     # We handle pydantic generic models separately as they don't have the same

tests/test_generics.py

@@ -735,6 +735,27 @@ class Model(GenericModel, Generic[t]):
         assert type(float_or_int_model(data='1').data) is float
 
 
+@pytest.mark.skipif(sys.version_info < (3, 10), reason='pep-604 syntax (Ex.: list | int) was added in python3.10')
+def test_generic_model_caching_detect_order_of_union_args_basic_with_pep_604_syntax(create_module):
+    # Basic variant of https://github.com/pydantic/pydantic/issues/4474 with pep-604 syntax.
+    @create_module
+    def module():
+        from typing import Generic, TypeVar
+
+        from pydantic.generics import GenericModel
+
+        t = TypeVar('t')
+
+        class Model(GenericModel, Generic[t]):
+            data: t
+
+        int_or_float_model = Model[int | float]
+        float_or_int_model = Model[float | int]
+
+        assert type(int_or_float_model(data='1').data) is int
+        assert type(float_or_int_model(data='1').data) is float
+
+
 @pytest.mark.skip(
     reason="""
 Depends on similar issue in CPython itself: https://github.com/python/cpython/issues/86483
@@ -854,6 +875,27 @@ class Model(GenericModel, Generic[T]):
         assert replace_types(list[Union[str, list, T]], {T: int}) == list[Union[str, list, int]]
 
 
+@pytest.mark.skipif(sys.version_info < (3, 10), reason='pep-604 syntax (Ex.: list | int) was added in python3.10')
+def test_replace_types_with_pep_604_syntax() -> None:
+    T = TypeVar('T')
+
+    class Model(GenericModel, Generic[T]):
+        a: T
+
+    assert replace_types(T | None, {T: int}) == int | None
+    assert replace_types(T | int | str, {T: float}) == float | int | str
+    assert replace_types(list[T] | None, {T: int}) == list[int] | None
+    assert replace_types(List[str | list | T], {T: int}) == List[str | list | int]
+    assert replace_types(list[str | list | T], {T: int}) == list[str | list | int]
+    assert replace_types(list[str | list | list[T]], {T: int}) == list[str | list | list[int]]
+    assert replace_types(list[Model[T] | None] | None, {T: T}) == list[Model[T] | None] | None
+    assert (
+        replace_types(T | list[T | list[T | list[T | None] | None] | None] | None, {T: int})
+        == int | list[int | list[int | list[int | None] | None] | None] | None
+    )
+    assert replace_types(list[list[list[T | None]]], {T: int}) == list[list[list[int | None]]]
+
+
 def test_replace_types_with_user_defined_generic_type_field():
     """Test that using user defined generic types as generic model fields are handled correctly."""
 
@@ -916,6 +958,68 @@ class NormalModel(BaseModel):
     assert inner_model.__concrete__ is True
 
 
+@pytest.mark.skipif(sys.version_info < (3, 10), reason='pep-604 syntax (Ex.: list | int) was added in python3.10')
+def test_wrapping_resolved_generic_with_pep_604_syntax() -> None:
+    T = TypeVar('T')
+
+    class InnerModel(GenericModel, Generic[T]):
+        generic: list[T] | None
+
+    class OuterModel(BaseModel):
+        wrapper: InnerModel[int]
+
+    with pytest.raises(ValidationError):
+        OuterModel(wrapper={'generic': ['string_instead_of_int']})
+    assert OuterModel(wrapper={'generic': [1]}).dict() == {'wrapper': {'generic': [1]}}
+
+
+@pytest.mark.skipif(sys.version_info < (3, 10), reason='pep-604 syntax (Ex.: list | int) was added in python3.10')
+def test_type_propagation_in_deep_generic_with_pep_604_syntax() -> None:
+    T = TypeVar('T')
+
+    class InnerModel(GenericModel, Generic[T]):
+        generic: list[T] | None
+
+    class OuterModel(GenericModel, Generic[T]):
+        wrapper: InnerModel[T] | None
+
+    with pytest.raises(ValidationError):
+        OuterModel[int](wrapper={'generic': ['string_instead_of_int']})
+    assert OuterModel[int](wrapper={'generic': [1]}) == {'wrapper': {'generic': [1]}}
+
+
+@pytest.mark.skipif(sys.version_info < (3, 10), reason='pep-604 syntax (Ex.: list | int) was added in python3.10')
+def test_deep_generic_with_pep_604_syntax() -> None:
+    T = TypeVar('T')
+    S = TypeVar('S')
+    R = TypeVar('R')
+
+    class OuterModel(GenericModel, Generic[T, S, R]):
+        a: Dict[R, list[T] | None]
+        b: S | R | None
+        c: R
+        d: float
+
+    class InnerModel(GenericModel, Generic[T, R]):
+        c: list[T] | None
+        d: list[R] | None
+
+    class NormalModel(BaseModel):
+        e: int
+        f: str
+
+    inner_model = InnerModel[int, str]
+    generic_model = OuterModel[inner_model, NormalModel, int]
+
+    inner_models = [inner_model(c=[1], d=['a'])]
+    generic_model(a={1: inner_models, 2: None}, b=None, c=1, d=1.5)
+    generic_model(a={}, b=NormalModel(e=1, f='a'), c=1, d=1.5)
+    generic_model(a={}, b=1, c=1, d=1.5)
+
+    assert InnerModel.__concrete__ is False
+    assert inner_model.__concrete__ is True
+
+
 def test_deep_generic_with_inner_typevar():
     T = TypeVar('T')