From 6cabfcfaf0ca1b9aa55df4c5fff1035ef6c7829e Mon Sep 17 00:00:00 2001
From: Matt Fulgo <matt@fulgo.org>
Date: Mon, 24 Oct 2022 14:40:19 -0400
Subject: [PATCH 1/2] Fix TypeError for GenericModel with Callable param

Introduced in 1.10.2, a TypeError would be raised upon creation of a
GenericModel class that used a Callable type parameter. This would
happen when `typing.get_args` returned a list for the first type
agruments in a Callable and pydantic would try to use the value as a
dictionary key. To avoid the issue, we convert the list to a tuple
before using it as a key.

The possible approach of modifying pydantic's `get_args` function to
return a tuple instead of a list didn't work out because the return
values are used in more places, some of which expect the list and not a
tuple.

Fixes #4551
---
 changes/4551-mfulgo.md |  1 +
 pydantic/generics.py   |  6 +++++-
 tests/test_generics.py | 27 +++++++++++++++++++++++++++
 3 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 changes/4551-mfulgo.md

diff --git a/changes/4551-mfulgo.md b/changes/4551-mfulgo.md
new file mode 100644
index 0000000000..ccd41c96e9
--- /dev/null
+++ b/changes/4551-mfulgo.md
@@ -0,0 +1 @@
+Fix GenericModel with Callable param raising a TypeError
diff --git a/pydantic/generics.py b/pydantic/generics.py
index a3f52bfee9..ece421e8ba 100644
--- a/pydantic/generics.py
+++ b/pydantic/generics.py
@@ -64,7 +64,11 @@ def __class_getitem__(cls: Type[GenericModelT], params: Union[Type[Any], Tuple[T
         """
 
         def _cache_key(_params: Any) -> Tuple[Type[GenericModelT], Any, Tuple[Any, ...]]:
-            return cls, _params, get_args(_params)
+            args = 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(params))
         if cached is not None:
diff --git a/tests/test_generics.py b/tests/test_generics.py
index 39adc45f20..371272b1ca 100644
--- a/tests/test_generics.py
+++ b/tests/test_generics.py
@@ -7,6 +7,7 @@
     ClassVar,
     Dict,
     Generic,
+    Iterable,
     List,
     Mapping,
     Optional,
@@ -234,6 +235,32 @@ 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(GenericModel, 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
+
+
 def test_generic_config():
     data_type = TypeVar('data_type')
 

From c24c5488cf1b95a367eb7d424cca27ab0e236e91 Mon Sep 17 00:00:00 2001
From: Samuel Colvin <samcolvin@gmail.com>
Date: Thu, 27 Oct 2022 16:19:00 +0100
Subject: [PATCH 2/2] change as markdown

---
 changes/4551-mfulgo.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/changes/4551-mfulgo.md b/changes/4551-mfulgo.md
index ccd41c96e9..1d9871a41a 100644
--- a/changes/4551-mfulgo.md
+++ b/changes/4551-mfulgo.md
@@ -1 +1 @@
-Fix GenericModel with Callable param raising a TypeError
+Fix `GenericModel` with `Callable` param raising a `TypeError`