Add PatchGenericPickle to fix pickle issue in celery notifications

lib/galaxy/schema/generics.py

@@ -1,12 +1,15 @@
+import sys
 from typing import (
     Any,
+    Generic,
     Tuple,
     Type,
     TypeVar,
 )
 
 from pydantic import BaseModel
 from pydantic.json_schema import GenerateJsonSchema
+from typing_extensions import override
 
 from galaxy.schema.fields import (
     DecodedDatabaseIdField,
@@ -50,3 +53,46 @@ def get_defs_ref(self, core_mode_ref):
             for i, choice in enumerate(choices):
                 choices[i] = choice.replace(choices[0], ref_to_name[ref])  # type: ignore[call-overload]
         return full_def
+
+
+class PatchGenericPickle:
+    """A mixin that allows generic pydantic models to be serialized and deserialized with pickle.
+
+    Notes
+    ----
+    In general, pickle shouldn't be encouraged as a means of serialization since there are better,
+    safer options. In some cases e.g. Streamlit's `@st.cache_data there's no getting around
+    needing to use pickle.
+
+    As of Pydantic 2.7, generics don't properly work with pickle. The core issue is the following
+    1. For each specialized generic, pydantic creates a new subclass at runtime. This class
+       has a `__qualname__` that contains the type var argument e.g. `"MyGeneric[str]"` for a
+       `class MyGeneric(BaseModel, Generic[T])`.
+    2. Pickle attempts to find a symbol with the value of `__qualname__` in the module where the
+       class was defined, which fails since Pydantic defines that class dynamically at runtime.
+       Pydantic does attempt to register these dynamic classes but currently only for classes
+       defined at the top-level of the interpreter.
+
+    See Also
+    --------
+    - https://github.com/pydantic/pydantic/issues/9390
+    """
+
+    @classmethod
+    @override
+    def __init_subclass__(cls, **kwargs):
+        # Note: we're still in __init_subclass__, not yet in __pydantic_init_subclass__
+        #  not all model_fields are available at this point.
+        super().__init_subclass__(**kwargs)
+
+        if not issubclass(cls, BaseModel):
+            raise TypeError("PatchGenericPickle can only be used with subclasses of pydantic.BaseModel")
+        if not issubclass(cls, Generic):  # type: ignore [arg-type]
+            raise TypeError("PatchGenericPickle can only be used with Generic models")
+
+        qualname = cls.__qualname__
+        declaring_module = sys.modules[cls.__module__]
+        if qualname not in declaring_module.__dict__:
+            # This should work in all cases, but we might need to make this check and update more
+            # involved e.g. see pydantic._internal._generics.create_generic_submodel
+            declaring_module.__dict__[qualname] = cls

lib/galaxy/schema/notifications.py

@@ -26,6 +26,7 @@
 from galaxy.schema.generics import (
     DatabaseIdT,
     GenericModel,
+    PatchGenericPickle,
 )
 from galaxy.schema.schema import Model
 from galaxy.schema.types import (
@@ -264,7 +265,7 @@ class NotificationCreateData(Model):
     )
 
 
-class GenericNotificationRecipients(GenericModel, Generic[DatabaseIdT]):
+class GenericNotificationRecipients(GenericModel, Generic[DatabaseIdT], PatchGenericPickle):
     """The recipients of a notification. Can be a combination of users, groups and roles."""
 
     user_ids: List[DatabaseIdT] = Field(