feat: add support for SQLAlchemy computed fields

polyfactory/factories/sqlalchemy_factory.py

@@ -178,6 +178,9 @@ def should_column_be_set(cls, column: Any) -> bool:
         if not cls.should_dataclass_init_field(column.name):
             return False
 
+        if column.computed and (cls.__session__ is not None or cls.__async_session__ is not None):
+            return False
+
         return bool(cls.__set_foreign_keys__ or not column.foreign_keys)
 
     @classmethod

tests/sqlalchemy_factory/models.py

@@ -1,7 +1,7 @@
 from dataclasses import dataclass
 from typing import Any, Optional
 
-from sqlalchemy import Boolean, Column, DateTime, ForeignKey, Integer, String, func, orm, text
+from sqlalchemy import Boolean, Column, Computed, DateTime, ForeignKey, Integer, String, func, orm, text
 from sqlalchemy.ext.associationproxy import association_proxy
 from sqlalchemy.orm import relationship
 from sqlalchemy.orm.decl_api import DeclarativeMeta, registry
@@ -146,3 +146,11 @@ class Employee(Base):
     name = Column(String)
     company_id = Column(Integer, ForeignKey("companies.id"))
     company = relationship(Company, back_populates="employees")
+
+
+class Shape(Base):
+    __tablename__ = "shape"
+
+    id = Column(Integer, primary_key=True)
+    side: Any = Column(Integer(), nullable=False, default=10)
+    area: Any = Column(Integer, Computed("side * side"), nullable=False)

tests/sqlalchemy_factory/test_sqlalchemy_factory_common.py

@@ -51,6 +51,7 @@
     CollectionChildMixin,
     CollectionParentMixin,
     NonSQLAchemyClass,
+    Shape,
     _registry,
 )
 from tests.sqlalchemy_factory.types import ListLike, SetLike
@@ -133,6 +134,34 @@ class ModelFactory(SQLAlchemyFactory[Model]): ...
     assert instance.age * 3 == instance.triple_age
 
 
+def test_computed_column_sync_persistence(engine: Engine) -> None:
+    Base.metadata.create_all(engine)
+
+    class ShapeFactory(SQLAlchemyFactory[Shape]):
+        __model__ = Shape
+        __session__ = Session(engine)
+
+    instance = ShapeFactory.create_sync()
+    assert instance.area == pow(instance.side, 2)
+
+
+async def test_computed_column_async_persistence(engine: Engine, async_engine: AsyncEngine) -> None:
+    class ShapeFactory(SQLAlchemyFactory[Shape]):
+        __model__ = Shape
+        __async_session__ = AsyncSession(async_engine)
+
+    instance = await ShapeFactory.create_async()
+    assert instance.area == pow(instance.side, 2)
+
+
+def test_computed_column_no_persistence() -> None:
+    class ShapeFactory(SQLAlchemyFactory[Shape]):
+        __model__ = Shape
+
+    fields = ShapeFactory.get_model_fields()
+    assert "area" in [field.name for field in fields]
+
+
 @pytest.mark.parametrize(
     "type_",
     tuple(SQLAlchemyFactory.get_sqlalchemy_types().keys()),