Support older versions

fastapi/_compat.py

@@ -10,6 +10,7 @@ from typing import (
     FrozenSet,
     List,
     Mapping,
+    Optional,
     Sequence,
     Set,
     Tuple,
@@ -143,7 +144,7 @@ if PYDANTIC_V2:
             exclude_unset: bool = False,
             exclude_defaults: bool = False,
             exclude_none: bool = False,
-            context: dict[str, Any] | None = None,
+            context: Optional[Dict[str, Any]]= None,
         ) -> Any:
             # What calls this code passes a value that already called
             # self._type_adapter.validate_python(value)

fastapi/routing.py

@@ -130,7 +130,7 @@ async def serialize_response(
     exclude_defaults: bool = False,
     exclude_none: bool = False,
     is_coroutine: bool = True,
-    context: dict[str, Any] | None = None,
+    context: Optional[Dict[str, Any]]= None,
 ) -> Any:
     if field:
         errors = []

tests/test_serialize_response_model.py

@@ -3,7 +3,7 @@ from typing import Dict, List, Optional
 import pytest
 from fastapi import FastAPI
 from fastapi._compat import PYDANTIC_VERSION
-from pydantic import BaseModel, Field, SerializationInfo, model_serializer
+from pydantic import BaseModel, Field, model_serializer
 from starlette.testclient import TestClient
 
 app = FastAPI()
@@ -15,7 +15,7 @@ class Item(BaseModel):
     owner_ids: Optional[List[int]] = None
 
     @model_serializer(mode="wrap")
-    def _serialize(self, handler, info: SerializationInfo | None = None):
+    def _serialize(self, handler, info):
         data = handler(self)
         if info.context and info.context.get("mode") == "FASTAPI":
             if "price" in data: