From ef0b8280efd36e1921efdbcd9696b0191703fa64 Mon Sep 17 00:00:00 2001
From: Mathieu Bressolle-Chataigner <mathieu.chataigner@gmail.com>
Date: Wed, 17 Jul 2024 00:05:13 +0200
Subject: [PATCH] catch PydanticUndefinedAnnotation in create_response_field

this exception may be raised when having some unresolvable forward refs
most probably when trying to return a complex SQLAlchemy object
---
 fastapi/_compat.py | 4 ++++
 fastapi/utils.py   | 3 ++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/fastapi/_compat.py b/fastapi/_compat.py
index 06b847b4f..4609cbe82 100644
--- a/fastapi/_compat.py
+++ b/fastapi/_compat.py
@@ -47,6 +47,7 @@ sequence_types = tuple(sequence_annotation_to_type.keys())
 
 if PYDANTIC_V2:
     from pydantic import PydanticSchemaGenerationError as PydanticSchemaGenerationError
+    from pydantic.errors import PydanticUndefinedAnnotation as PydanticUndefinedAnnotation
     from pydantic import TypeAdapter
     from pydantic import ValidationError as ValidationError
     from pydantic._internal._schema_generation_shared import (  # type: ignore[attr-defined]
@@ -358,6 +359,9 @@ else:
     class PydanticSchemaGenerationError(Exception):  # type: ignore[no-redef]
         pass
 
+    class PydanticUndefinedAnnotation(Exception):  # type: ignore[no-redef]
+        pass
+
     def with_info_plain_validator_function(  # type: ignore[misc]
         function: Callable[..., Any],
         *,
diff --git a/fastapi/utils.py b/fastapi/utils.py
index dfda4e678..eaa332709 100644
--- a/fastapi/utils.py
+++ b/fastapi/utils.py
@@ -20,6 +20,7 @@ from fastapi._compat import (
     BaseConfig,
     ModelField,
     PydanticSchemaGenerationError,
+    PydanticUndefinedAnnotation,
     Undefined,
     UndefinedType,
     Validator,
@@ -97,7 +98,7 @@ def create_response_field(
         )
     try:
         return ModelField(**kwargs)  # type: ignore[arg-type]
-    except (RuntimeError, PydanticSchemaGenerationError):
+    except (RuntimeError, PydanticSchemaGenerationError, PydanticUndefinedAnnotation):
         raise fastapi.exceptions.FastAPIError(
             "Invalid args for response field! Hint: "
             f"check that {type_} is a valid Pydantic field type. "