feat: add sort_params helper in CrudFactory

docs/reference/exceptions.md

@@ -13,6 +13,7 @@ from fastapi_toolsets.exceptions import (
     ConflictError,
     NoSearchableFieldsError,
     InvalidFacetFilterError,
+    InvalidSortFieldError,
     generate_error_responses,
     init_exceptions_handlers,
 )
@@ -32,6 +33,8 @@ from fastapi_toolsets.exceptions import (
 
 ## ::: fastapi_toolsets.exceptions.exceptions.InvalidFacetFilterError
 
+## ::: fastapi_toolsets.exceptions.exceptions.InvalidSortFieldError
+
 ## ::: fastapi_toolsets.exceptions.exceptions.generate_error_responses
 
 ## ::: fastapi_toolsets.exceptions.handler.init_exceptions_handlers

src/fastapi_toolsets/crud/__init__.py

@@ -1,7 +1,7 @@
 """Generic async CRUD operations for SQLAlchemy models."""
 
 from ..exceptions import InvalidFacetFilterError, NoSearchableFieldsError
-from .factory import CrudFactory, JoinType, M2MFieldType
+from .factory import CrudFactory, JoinType, M2MFieldType, OrderByClause
 from .search import (
     FacetFieldType,
     SearchConfig,
@@ -16,5 +16,6 @@ __all__ = [
     "JoinType",
     "M2MFieldType",
     "NoSearchableFieldsError",
+    "OrderByClause",
     "SearchConfig",
 ]

src/fastapi_toolsets/crud/factory.py

@@ -21,10 +21,11 @@ from sqlalchemy.exc import NoResultFound
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.orm import DeclarativeBase, QueryableAttribute, selectinload
 from sqlalchemy.sql.base import ExecutableOption
+from sqlalchemy.sql.elements import ColumnElement
 from sqlalchemy.sql.roles import WhereHavingRole
 
 from ..db import get_transaction
-from ..exceptions import NotFoundError
+from ..exceptions import InvalidSortFieldError, NotFoundError
 from ..schemas import CursorPagination, OffsetPagination, PaginatedResponse, Response
 from .search import (
     FacetFieldType,
@@ -40,6 +41,7 @@ ModelType = TypeVar("ModelType", bound=DeclarativeBase)
 SchemaType = TypeVar("SchemaType", bound=BaseModel)
 JoinType = list[tuple[type[DeclarativeBase], Any]]
 M2MFieldType = Mapping[str, QueryableAttribute[Any]]
+OrderByClause = ColumnElement[Any] | QueryableAttribute[Any]
 
 
 def _encode_cursor(value: Any) -> str:
@@ -61,6 +63,7 @@ class AsyncCrud(Generic[ModelType]):
     model: ClassVar[type[DeclarativeBase]]
     searchable_fields: ClassVar[Sequence[SearchFieldType] | None] = None
     facet_fields: ClassVar[Sequence[FacetFieldType] | None] = None
+    sort_fields: ClassVar[Sequence[QueryableAttribute[Any]] | None] = None
     m2m_fields: ClassVar[M2MFieldType | None] = None
     default_load_options: ClassVar[list[ExecutableOption] | None] = None
     cursor_column: ClassVar[Any | None] = None
@@ -176,6 +179,63 @@ class AsyncCrud(Generic[ModelType]):
 
         return dependency
 
+    @classmethod
+    def sort_params(
+        cls: type[Self],
+        *,
+        sort_fields: Sequence[QueryableAttribute[Any]] | None = None,
+        default_field: QueryableAttribute[Any] | None = None,
+        default_order: Literal["asc", "desc"] = "asc",
+    ) -> Callable[..., Awaitable[OrderByClause | None]]:
+        """Return a FastAPI dependency that resolves sort query params into an order_by clause.
+
+        Args:
+            sort_fields: Override the allowed sort fields. Falls back to the class-level
+                ``sort_fields`` if not provided.
+            default_field: Field to sort by when ``sort_by`` query param is absent.
+                If ``None`` and no ``sort_by`` is provided, no ordering is applied.
+            default_order: Default sort direction when ``sort_order`` is absent
+                (``"asc"`` or ``"desc"``).
+
+        Returns:
+            An async dependency function named ``{Model}SortParams`` that resolves to an
+            ``OrderByClause`` (or ``None``). Pass it to ``Depends()`` in your route.
+
+        Raises:
+            ValueError: If no sort fields are configured on this CRUD class and none are
+                provided via ``sort_fields``.
+            InvalidSortFieldError: When the request provides an unknown ``sort_by`` value.
+        """
+        fields = sort_fields if sort_fields is not None else cls.sort_fields
+        if not fields:
+            raise ValueError(
+                f"{cls.__name__} has no sort_fields configured. "
+                "Pass sort_fields= or set them on CrudFactory."
+            )
+        field_map: dict[str, QueryableAttribute[Any]] = {f.key: f for f in fields}
+        valid_keys = sorted(field_map.keys())
+
+        async def dependency(
+            sort_by: str | None = Query(
+                None, description=f"Field to sort by. Valid values: {valid_keys}"
+            ),
+            sort_order: Literal["asc", "desc"] = Query(
+                default_order, description="Sort direction"
+            ),
+        ) -> OrderByClause | None:
+            if sort_by is None:
+                if default_field is None:
+                    return None
+                field = default_field
+            elif sort_by not in field_map:
+                raise InvalidSortFieldError(sort_by, valid_keys)
+            else:
+                field = field_map[sort_by]
+            return field.asc() if sort_order == "asc" else field.desc()
+
+        dependency.__name__ = f"{cls.model.__name__}SortParams"
+        return dependency
+
     @overload
     @classmethod
     async def create(  # pragma: no cover
@@ -415,7 +475,7 @@ class AsyncCrud(Generic[ModelType]):
         joins: JoinType | None = None,
         outer_join: bool = False,
         load_options: list[ExecutableOption] | None = None,
-        order_by: Any | None = None,
+        order_by: OrderByClause | None = None,
         limit: int | None = None,
         offset: int | None = None,
     ) -> Sequence[ModelType]:
@@ -745,7 +805,7 @@ class AsyncCrud(Generic[ModelType]):
         joins: JoinType | None = None,
         outer_join: bool = False,
         load_options: list[ExecutableOption] | None = None,
-        order_by: Any | None = None,
+        order_by: OrderByClause | None = None,
         page: int = 1,
         items_per_page: int = 20,
         search: str | SearchConfig | None = None,
@@ -766,7 +826,7 @@ class AsyncCrud(Generic[ModelType]):
         joins: JoinType | None = None,
         outer_join: bool = False,
         load_options: list[ExecutableOption] | None = None,
-        order_by: Any | None = None,
+        order_by: OrderByClause | None = None,
         page: int = 1,
         items_per_page: int = 20,
         search: str | SearchConfig | None = None,
@@ -785,7 +845,7 @@ class AsyncCrud(Generic[ModelType]):
         joins: JoinType | None = None,
         outer_join: bool = False,
         load_options: list[ExecutableOption] | None = None,
-        order_by: Any | None = None,
+        order_by: OrderByClause | None = None,
         page: int = 1,
         items_per_page: int = 20,
         search: str | SearchConfig | None = None,
@@ -937,7 +997,7 @@ class AsyncCrud(Generic[ModelType]):
         joins: JoinType | None = None,
         outer_join: bool = False,
         load_options: list[ExecutableOption] | None = None,
-        order_by: Any | None = None,
+        order_by: OrderByClause | None = None,
         items_per_page: int = 20,
         search: str | SearchConfig | None = None,
         search_fields: Sequence[SearchFieldType] | None = None,
@@ -958,7 +1018,7 @@ class AsyncCrud(Generic[ModelType]):
         joins: JoinType | None = None,
         outer_join: bool = False,
         load_options: list[ExecutableOption] | None = None,
-        order_by: Any | None = None,
+        order_by: OrderByClause | None = None,
         items_per_page: int = 20,
         search: str | SearchConfig | None = None,
         search_fields: Sequence[SearchFieldType] | None = None,
@@ -977,7 +1037,7 @@ class AsyncCrud(Generic[ModelType]):
         joins: JoinType | None = None,
         outer_join: bool = False,
         load_options: list[ExecutableOption] | None = None,
-        order_by: Any | None = None,
+        order_by: OrderByClause | None = None,
         items_per_page: int = 20,
         search: str | SearchConfig | None = None,
         search_fields: Sequence[SearchFieldType] | None = None,
@@ -1147,6 +1207,7 @@ def CrudFactory(
     *,
     searchable_fields: Sequence[SearchFieldType] | None = None,
     facet_fields: Sequence[FacetFieldType] | None = None,
+    sort_fields: Sequence[QueryableAttribute[Any]] | None = None,
     m2m_fields: M2MFieldType | None = None,
     default_load_options: list[ExecutableOption] | None = None,
     cursor_column: Any | None = None,
@@ -1159,6 +1220,8 @@ def CrudFactory(
         facet_fields: Optional list of columns to compute distinct values for in paginated
             responses. Supports direct columns (``User.status``) and relationship tuples
             (``(User.role, Role.name)``). Can be overridden per call.
+        sort_fields: Optional list of model attributes that callers are allowed to sort by
+            via ``sort_params()``. Can be overridden per call.
         m2m_fields: Optional mapping for many-to-many relationships.
             Maps schema field names (containing lists of IDs) to
             SQLAlchemy relationship attributes.
@@ -1252,6 +1315,7 @@ def CrudFactory(
             "model": model,
             "searchable_fields": searchable_fields,
             "facet_fields": facet_fields,
+            "sort_fields": sort_fields,
             "m2m_fields": m2m_fields,
             "default_load_options": default_load_options,
             "cursor_column": cursor_column,

src/fastapi_toolsets/exceptions/__init__.py

@@ -6,6 +6,7 @@ from .exceptions import (
     ConflictError,
     ForbiddenError,
     InvalidFacetFilterError,
+    InvalidSortFieldError,
     NoSearchableFieldsError,
     NotFoundError,
     UnauthorizedError,
@@ -21,6 +22,7 @@ __all__ = [
     "generate_error_responses",
     "init_exceptions_handlers",
     "InvalidFacetFilterError",
+    "InvalidSortFieldError",
     "NoSearchableFieldsError",
     "NotFoundError",
     "UnauthorizedError",

src/fastapi_toolsets/exceptions/exceptions.py

@@ -128,6 +128,31 @@ class InvalidFacetFilterError(ApiException):
         super().__init__(detail)
 
 
+class InvalidSortFieldError(ApiException):
+    """Raised when sort_by contains a field not in the allowed sort fields."""
+
+    api_error = ApiError(
+        code=422,
+        msg="Invalid Sort Field",
+        desc="The requested sort field is not allowed for this resource.",
+        err_code="SORT-422",
+    )
+
+    def __init__(self, field: str, valid_fields: list[str]) -> None:
+        """Initialize the exception.
+
+        Args:
+            field: The unknown sort field provided by the caller
+            valid_fields: List of valid field names
+        """
+        self.field = field
+        self.valid_fields = valid_fields
+        detail = (
+            f"'{field}' is not an allowed sort field. Valid fields: {valid_fields}."
+        )
+        super().__init__(detail)
+
+
 def generate_error_responses(
     *errors: type[ApiException],
 ) -> dict[int | str, dict[str, Any]]:

tests/test_crud_search.py

@@ -1,9 +1,11 @@
 """Tests for CRUD search functionality."""
 
+import inspect
 import uuid
 
 import pytest
 from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.sql.elements import ColumnElement, UnaryExpression
 
 from fastapi_toolsets.crud import (
     CrudFactory,
@@ -11,6 +13,7 @@ from fastapi_toolsets.crud import (
     SearchConfig,
     get_searchable_fields,
 )
+from fastapi_toolsets.exceptions import InvalidSortFieldError
 from fastapi_toolsets.schemas import OffsetPagination
 
 from .conftest import (
@@ -1014,3 +1017,144 @@ class TestFilterParamsSchema:
 
         assert isinstance(result.pagination, OffsetPagination)
         assert result.pagination.total_count == 2
+
+
+class TestSortParamsSchema:
+    """Tests for AsyncCrud.sort_params()."""
+
+    def test_generates_sort_by_and_sort_order_params(self):
+        """Returned dependency has sort_by and sort_order query params."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username, User.email])
+        dep = UserSortCrud.sort_params()
+
+        param_names = set(inspect.signature(dep).parameters)
+        assert param_names == {"sort_by", "sort_order"}
+
+    def test_dependency_name_includes_model_name(self):
+        """Dependency function is named after the model."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep = UserSortCrud.sort_params()
+        assert getattr(dep, "__name__") == "UserSortParams"
+
+    def test_raises_when_no_sort_fields(self):
+        """ValueError raised when no sort_fields are configured or provided."""
+        with pytest.raises(ValueError, match="no sort_fields"):
+            UserCrud.sort_params()
+
+    def test_sort_fields_override(self):
+        """sort_fields= parameter overrides the class-level default."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username, User.email])
+        dep = UserSortCrud.sort_params(sort_fields=[User.email])
+
+        param_names = set(inspect.signature(dep).parameters)
+        assert "sort_by" in param_names
+        # description should only mention email, not username
+        sig = inspect.signature(dep)
+        description = sig.parameters["sort_by"].default.description
+        assert "email" in description
+        assert "username" not in description
+
+    def test_sort_by_description_lists_valid_fields(self):
+        """sort_by query param description mentions each allowed field."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username, User.email])
+        dep = UserSortCrud.sort_params()
+
+        sig = inspect.signature(dep)
+        description = sig.parameters["sort_by"].default.description
+        assert "username" in description
+        assert "email" in description
+
+    def test_default_order_reflected_in_sort_order_default(self):
+        """default_order is used as the default value for sort_order."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep_asc = UserSortCrud.sort_params(default_order="asc")
+        dep_desc = UserSortCrud.sort_params(default_order="desc")
+
+        sig_asc = inspect.signature(dep_asc)
+        sig_desc = inspect.signature(dep_desc)
+        assert sig_asc.parameters["sort_order"].default.default == "asc"
+        assert sig_desc.parameters["sort_order"].default.default == "desc"
+
+    @pytest.mark.anyio
+    async def test_no_sort_by_no_default_returns_none(self):
+        """Returns None when sort_by is absent and no default_field is set."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep = UserSortCrud.sort_params()
+        result = await dep(sort_by=None, sort_order="asc")
+        assert result is None
+
+    @pytest.mark.anyio
+    async def test_no_sort_by_with_default_field_returns_asc_expression(self):
+        """Returns default_field.asc() when sort_by absent and sort_order=asc."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep = UserSortCrud.sort_params(default_field=User.username)
+        result = await dep(sort_by=None, sort_order="asc")
+        assert isinstance(result, UnaryExpression)
+        assert "ASC" in str(result)
+
+    @pytest.mark.anyio
+    async def test_no_sort_by_with_default_field_returns_desc_expression(self):
+        """Returns default_field.desc() when sort_by absent and sort_order=desc."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep = UserSortCrud.sort_params(default_field=User.username)
+        result = await dep(sort_by=None, sort_order="desc")
+        assert isinstance(result, UnaryExpression)
+        assert "DESC" in str(result)
+
+    @pytest.mark.anyio
+    async def test_valid_sort_by_asc(self):
+        """Returns field.asc() for a valid sort_by with sort_order=asc."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep = UserSortCrud.sort_params()
+        result = await dep(sort_by="username", sort_order="asc")
+        assert isinstance(result, UnaryExpression)
+        assert "ASC" in str(result)
+
+    @pytest.mark.anyio
+    async def test_valid_sort_by_desc(self):
+        """Returns field.desc() for a valid sort_by with sort_order=desc."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep = UserSortCrud.sort_params()
+        result = await dep(sort_by="username", sort_order="desc")
+        assert isinstance(result, UnaryExpression)
+        assert "DESC" in str(result)
+
+    @pytest.mark.anyio
+    async def test_invalid_sort_by_raises_invalid_sort_field_error(self):
+        """Raises InvalidSortFieldError for an unknown sort_by value."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        dep = UserSortCrud.sort_params()
+        with pytest.raises(InvalidSortFieldError) as exc_info:
+            await dep(sort_by="nonexistent", sort_order="asc")
+        assert exc_info.value.field == "nonexistent"
+        assert "username" in exc_info.value.valid_fields
+
+    @pytest.mark.anyio
+    async def test_multiple_fields_all_resolve(self):
+        """All configured fields resolve correctly via sort_by."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username, User.email])
+        dep = UserSortCrud.sort_params()
+        result_username = await dep(sort_by="username", sort_order="asc")
+        result_email = await dep(sort_by="email", sort_order="desc")
+        assert isinstance(result_username, ColumnElement)
+        assert isinstance(result_email, ColumnElement)
+
+    @pytest.mark.anyio
+    async def test_sort_params_integrates_with_get_multi(
+        self, db_session: AsyncSession
+    ):
+        """sort_params output is accepted by get_multi(order_by=...)."""
+        UserSortCrud = CrudFactory(User, sort_fields=[User.username])
+        await UserCrud.create(
+            db_session, UserCreate(username="charlie", email="c@test.com")
+        )
+        await UserCrud.create(
+            db_session, UserCreate(username="alice", email="a@test.com")
+        )
+
+        dep = UserSortCrud.sort_params()
+        order_by = await dep(sort_by="username", sort_order="asc")
+        results = await UserSortCrud.get_multi(db_session, order_by=order_by)
+
+        assert results[0].username == "alice"
+        assert results[1].username == "charlie"

tests/test_exceptions.py

@@ -8,6 +8,7 @@ from fastapi_toolsets.exceptions import (
     ApiException,
     ConflictError,
     ForbiddenError,
+    InvalidSortFieldError,
     NotFoundError,
     UnauthorizedError,
     generate_error_responses,
@@ -334,3 +335,43 @@ class TestExceptionIntegration:
 
         assert response.status_code == 200
         assert response.json() == {"id": 1}
+
+
+class TestInvalidSortFieldError:
+    """Tests for InvalidSortFieldError exception."""
+
+    def test_api_error_attributes(self):
+        """InvalidSortFieldError has correct api_error metadata."""
+        assert InvalidSortFieldError.api_error.code == 422
+        assert InvalidSortFieldError.api_error.err_code == "SORT-422"
+        assert InvalidSortFieldError.api_error.msg == "Invalid Sort Field"
+
+    def test_stores_field_and_valid_fields(self):
+        """InvalidSortFieldError stores field and valid_fields on the instance."""
+        error = InvalidSortFieldError("unknown", ["name", "created_at"])
+        assert error.field == "unknown"
+        assert error.valid_fields == ["name", "created_at"]
+
+    def test_message_contains_field_and_valid_fields(self):
+        """Exception message mentions the bad field and valid options."""
+        error = InvalidSortFieldError("bad_field", ["name", "email"])
+        assert "bad_field" in str(error)
+        assert "name" in str(error)
+        assert "email" in str(error)
+
+    def test_handled_as_422_by_exception_handler(self):
+        """init_exceptions_handlers turns InvalidSortFieldError into a 422 response."""
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        @app.get("/items")
+        async def list_items():
+            raise InvalidSortFieldError("bad", ["name"])
+
+        client = TestClient(app)
+        response = client.get("/items")
+
+        assert response.status_code == 422
+        data = response.json()
+        assert data["error_code"] == "SORT-422"
+        assert data["status"] == "FAIL"