fix: avoid "Expected enum but got int" serializer warnings for ch…

…ats API (#602)

close #560

Currently, the warning has only been observed in the Chat-related APIs,
and it may not be fully resolved. Test API: GET /api/v1/chats.

---------

Co-authored-by: Mini256 <[email protected]>

backend/app/alembic/versions/2adc0b597dcd_int_enum_type.py

@@ -0,0 +1,42 @@
+"""int_enum_type
+
+Revision ID: 2adc0b597dcd
+Revises: a54f966436ce
+Create Date: 2025-01-24 17:58:08.339090
+
+"""
+
+from alembic import op
+from sqlalchemy.dialects import mysql
+
+from app.models.base import IntEnumType
+
+# revision identifiers, used by Alembic.
+revision = "2adc0b597dcd"
+down_revision = "a54f966436ce"
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.alter_column(
+        "chats",
+        "visibility",
+        existing_type=mysql.SMALLINT(),
+        type_=IntEnumType(),
+        existing_nullable=False,
+    )
+    # ### end Alembic commands ###
+
+
+def downgrade():
+    # ### commands auto generated by Alembic - please adjust! ###
+    op.alter_column(
+        "chats",
+        "visibility",
+        existing_type=IntEnumType(),
+        type_=mysql.SMALLINT(),
+        existing_nullable=False,
+    )
+    # ### end Alembic commands ###

backend/app/models/base.py

@@ -2,9 +2,8 @@
 from uuid import UUID
 from datetime import datetime
 from typing import Optional
-
 from sqlmodel import Field, DateTime, func, SQLModel
-from sqlalchemy.types import TypeDecorator, LargeBinary
+from sqlalchemy.types import TypeDecorator, LargeBinary, Integer
 
 from app.utils.uuid6 import uuid7
 from app.utils.aes import AESCipher
@@ -52,3 +51,35 @@ def process_result_value(self, value, dialect):
             json_str = AESCipher(get_aes_key()).decrypt(value)
             return json.loads(json_str)
         return value
+
+
+class IntEnumType(TypeDecorator):
+    """
+    IntEnumType is a custom TypeDecorator that handles conversion between
+    integer values in the database and Enum types in Python.
+
+    This replaces the previous SmallInteger implementation to resolve Pydantic
+    serialization warnings. When using SmallInteger, SQLAlchemy would return raw
+    integers from the database (e.g., 0 or 1), causing Pydantic validation warnings
+    since it expects proper Enum types.
+    """
+
+    impl = Integer
+
+    def __init__(self, enum_class, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.enum_class = enum_class
+
+    def process_bind_param(self, value, dialect):
+        # enum -> int
+        if isinstance(value, self.enum_class):
+            return value.value
+        elif value is None:
+            return None
+        raise ValueError(f"Invalid value for {self.enum_class}: {value}")
+
+    def process_result_value(self, value, dialect):
+        # int -> enum
+        if value is not None:
+            return self.enum_class(value)
+        return None

backend/app/models/chat.py

@@ -9,11 +9,10 @@
     Column,
     DateTime,
     JSON,
-    SmallInteger,
     Relationship as SQLRelationship,
 )
 
-from .base import UUIDBaseModel, UpdatableBaseModel
+from .base import IntEnumType, UUIDBaseModel, UpdatableBaseModel
 
 
 class ChatVisibility(int, enum.Enum):
@@ -43,7 +42,11 @@ class Chat(UUIDBaseModel, UpdatableBaseModel, table=True):
     browser_id: str = Field(max_length=50, nullable=True)
     origin: str = Field(max_length=256, default=None, nullable=True)
     visibility: ChatVisibility = Field(
-        sa_column=Column(SmallInteger, default=ChatVisibility.PRIVATE, nullable=False)
+        sa_column=Column(
+            IntEnumType(ChatVisibility),
+            nullable=False,
+            default=ChatVisibility.PRIVATE,
+        )
     )
 
     __tablename__ = "chats"