Add fix for pydantic#4551 - ensure cache keys are hashable

pydantic/main.py

@@ -602,7 +602,11 @@ def __repr_args__(self) -> _repr.ReprArgs:
 
     def __class_getitem__(cls, typevar_values: type[Any] | tuple[type[Any], ...]) -> type[Any]:
         def _cache_key(_params: Any) -> tuple[type[Any], Any, tuple[Any, ...]]:
-            return cls, _params, typing_extensions.get_args(_params)
+            args = typing.get_args(_params)
+            # python returns a list for Callables, which is not hashable
+            if len(args) == 2 and isinstance(args[0], list):
+                args = (tuple(args[0]), args[1])
+            return cls, _params, args
 
         cached = _generic_types_cache.get(_cache_key(typevar_values))
         if cached is not None:

tests/test_generics.py

@@ -7,6 +7,7 @@
     ClassVar,
     Dict,
     Generic,
+    Iterable,
     List,
     Mapping,
     Optional,
@@ -21,7 +22,8 @@
 from typing_extensions import Annotated, Literal
 
 from pydantic import BaseModel, Field, Json, ValidationError, root_validator, validator
-from pydantic.generics import GenericModel, _generic_types_cache, iter_contained_typevars, replace_types
+from pydantic.generics import GenericModel, iter_contained_typevars, replace_types
+from pydantic.main import _generic_types_cache
 
 
 def test_generic_name():
@@ -241,6 +243,32 @@ class Model(GenericModel, Generic[T]):
     assert len(_generic_types_cache) == cache_size + 2
 
 
+def test_cache_keys_are_hashable():
+    cache_size = len(_generic_types_cache)
+    T = TypeVar('T')
+    C = Callable[[str, Dict[str, Any]], Iterable[str]]
+
+    class MyGenericModel(BaseModel, Generic[T]):
+        t: T
+
+    # Callable's first params get converted to a list, which is not hashable.
+    # Make sure we can handle that special case
+    Simple = MyGenericModel[Callable[[int], str]]
+    assert len(_generic_types_cache) == cache_size + 2
+    # Nested Callables
+    MyGenericModel[Callable[[C], Iterable[str]]]
+    assert len(_generic_types_cache) == cache_size + 4
+    MyGenericModel[Callable[[Simple], Iterable[int]]]
+    assert len(_generic_types_cache) == cache_size + 6
+    MyGenericModel[Callable[[MyGenericModel[C]], Iterable[int]]]
+    assert len(_generic_types_cache) == cache_size + 10
+
+    class Model(BaseModel):
+        x: MyGenericModel[Callable[[C], Iterable[str]]] = Field(...)
+
+    assert len(_generic_types_cache) == cache_size + 10
+
+
 @pytest.mark.xfail(reason='working on V2')
 def test_generic_config():
     data_type = TypeVar('data_type')