Add `awaitable_attrs` to rx.Model

This works like sqlalchemy's AsyncAttrs mixin, providing an async-context for
accessing fields and relationships when using async sessions.

reflex/model.py

@@ -5,7 +5,7 @@ from __future__ import annotations
 import re
 from collections import defaultdict
 from contextlib import suppress
-from typing import Any, ClassVar, Optional, Type, Union
+from typing import Any, Awaitable, ClassVar, Optional, Type, Union
 
 import alembic.autogenerate
 import alembic.command
@@ -19,6 +19,7 @@ import sqlalchemy.exc
 import sqlalchemy.ext.asyncio
 import sqlalchemy.orm
 from alembic.runtime.migration import MigrationContext
+from sqlalchemy.util.concurrency import greenlet_spawn
 
 from reflex.base import Base
 from reflex.config import environment, get_config
@@ -243,6 +244,18 @@ class ModelRegistry:
         return metadata
 
 
+class _AsyncAttrGetitem:
+    __slots__ = "_instance"
+
+    def __init__(self, _instance: Model):
+        self._instance = _instance
+
+    def __getattr__(self, name: str) -> Awaitable[Any]:
+        if name.startswith("_"):
+            return getattr(self._instance, name)
+        return greenlet_spawn(getattr, self._instance, name)
+
+
 class Model(Base, sqlmodel.SQLModel):  # pyright: ignore [reportGeneralTypeIssues,reportIncompatibleVariableOverride]
     """Base class to define a table in the database."""
 
@@ -261,6 +274,15 @@ class Model(Base, sqlmodel.SQLModel):  # pyright: ignore [reportGeneralTypeIssue
 
         super().__init_subclass__()
 
+    @property
+    def awaitable_attrs(self) -> _AsyncAttrGetitem:
+        """Provide a namespace of all attributes on this object wrapped as awaitables.
+
+        Returns:
+            An awaitable attribute namespace.
+        """
+        return _AsyncAttrGetitem(self)
+
     @classmethod
     def _dict_recursive(cls, value: Any):
         """Recursively serialize the relationship object(s).