Add better logic for scalars unwrapping (#1281)

examples/pagination_sqlalchemy.py

@@ -5,7 +5,7 @@
 from faker import Faker
 from fastapi import Depends, FastAPI
 from pydantic import BaseModel
-from sqlalchemy import create_engine, select, text
+from sqlalchemy import create_engine, select
 from sqlalchemy.orm import DeclarativeBase, Mapped, MappedAsDataclass, Session, mapped_column
 
 from fastapi_pagination import LimitOffsetPage, Page, add_pagination
@@ -74,7 +74,7 @@ def create_user(user_in: UserIn, db: Session = Depends(get_db)) -> UserOut:
 @app.get("/users/default", response_model=Page[UserOut])
 @app.get("/users/limit-offset", response_model=LimitOffsetPage[UserOut])
 def get_users(db: Session = Depends(get_db)) -> Any:
-    return paginate(db, select(User).from_statement(text("""SELECT * FROM users""")))
+    return paginate(db, select(User))
 
 
 if __name__ == "__main__":

fastapi_pagination/ext/sqlalchemy.py

@@ -18,7 +18,7 @@
 from sqlalchemy.exc import InvalidRequestError
 from sqlalchemy.orm import FromStatement, Query, Session, noload, scoped_session
 from sqlalchemy.sql.elements import TextClause
-from typing_extensions import TypeAlias, deprecated
+from typing_extensions import TypeAlias, deprecated, no_type_check
 
 from ..api import apply_items_transformer, create_page
 from ..bases import AbstractPage, AbstractParams, is_cursor
@@ -64,6 +64,14 @@ def __init__(self, *_: Any, **__: Any) -> None:
 Selectable: TypeAlias = "Union[Select, TextClause, FromStatement]"
 
 
+@no_type_check
+def _should_unwrap_scalars(query: Selectable) -> bool:
+    try:
+        return len(query.column_descriptions) == 1 and len(query.columns) > 1
+    except AttributeError:
+        return True
+
+
 def create_paginate_query_from_text(query: str, params: AbstractParams) -> str:
     raw_params = params.to_raw_params().as_limit_offset()
 
@@ -174,7 +182,9 @@ def _apply_items_transformer(*args: Any, **kwargs: Any) -> Any:
             per_page=raw_params.size,
             page=raw_params.cursor,  # type: ignore[arg-type]
         )
-        items = unwrap_scalars([*page])
+        items = [*page]
+        if _should_unwrap_scalars(query):
+            items = unwrap_scalars(items)
         items = _apply_items_transformer(items, transformer)
 
         return create_page(
@@ -190,7 +200,8 @@ def _apply_items_transformer(*args: Any, **kwargs: Any) -> Any:
 
     query = create_paginate_query(query, params)
     items = _maybe_unique(conn.execute(query), unique)
-    items = unwrap_scalars(items)
+    if _should_unwrap_scalars(query):
+        items = unwrap_scalars(items)
     items = _apply_items_transformer(items, transformer)
 
     return create_page(