fix: Respect init parameter for SQLAlchemy dataclasses (#793)

Co-authored-by: Andrew Truong <40660973+adhtruong@users.noreply.github.com>

Author: AlexPetul

polyfactory/factories/sqlalchemy_factory.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Collection, Mapping
+from dataclasses import is_dataclass
 from datetime import date, datetime
 from typing import (
     TYPE_CHECKING,
@@ -174,8 +175,22 @@ def should_column_be_set(cls, column: Any) -> bool:
         if not cls.__set_primary_key__ and column.primary_key:
             return False
 
+        if not cls.should_dataclass_init_field(column.name):
+            return False
+
         return bool(cls.__set_foreign_keys__ or not column.foreign_keys)
 
+    @classmethod
+    def should_dataclass_init_field(cls, field_name: str) -> bool:
+        if not is_dataclass(cls.__model__):
+            return True
+
+        dataclass_fields = cls.__model__.__dataclass_fields__
+        try:
+            return dataclass_fields[field_name].init
+        except KeyError:
+            return True
+
     @classmethod
     def _get_type_from_type_engine(cls, type_engine: TypeEngine) -> type:
         if type(type_engine) in cls.get_sqlalchemy_types():
@@ -285,6 +300,9 @@ def get_model_fields(cls) -> list[FieldMeta]:
         )
         if cls.__set_relationships__:
             for name, relationship in table.relationships.items():
+                if not cls.should_dataclass_init_field(name):
+                    continue
+
                 annotation = cls._get_relationship_type(relationship)
                 fields_meta.append(
                     FieldMeta.from_type(
@@ -295,6 +313,9 @@ def get_model_fields(cls) -> list[FieldMeta]:
         if cls.__set_association_proxy__:
             for name, attr in table.all_orm_descriptors.items():
                 if isinstance(attr, AssociationProxy):
+                    if not cls.should_dataclass_init_field(name):
+                        continue
+
                     # Read-only proxies derive from the underlying relationship and shouldn't be set directly.
                     if not getattr(attr, "creator", None):
                         continue

tests/sqlalchemy_factory/test_sqlalchemy_factory_v2.py

@@ -4,11 +4,12 @@
 from uuid import UUID
 
 import pytest
-from sqlalchemy import Text, __version__, orm, types
+from sqlalchemy import ForeignKey, Text, __version__, orm, types
 from sqlalchemy.dialects.mssql import JSON as MSSQL_JSON
 from sqlalchemy.dialects.mysql import JSON as MYSQL_JSON
 from sqlalchemy.dialects.postgresql import ARRAY, CIDR, HSTORE, INET, JSON, JSONB
 from sqlalchemy.dialects.sqlite import JSON as SQLITE_JSON
+from sqlalchemy.ext.associationproxy import AssociationProxy, association_proxy
 from sqlalchemy.ext.mutable import MutableDict, MutableList
 
 from polyfactory.factories.sqlalchemy_factory import SQLAlchemyFactory
@@ -132,3 +133,44 @@ class ModelFactory(SQLAlchemyFactory[Model]):
 
     instance = ModelFactory.build()
     assert instance.overridden is not None
+
+
+def test_dataclass_mapped_do_not_init_field() -> None:
+    class Base(orm.DeclarativeBase): ...
+
+    class Parent(orm.MappedAsDataclass, Base):
+        __tablename__ = "tesT_model"
+
+        id: orm.Mapped[int] = orm.mapped_column(primary_key=True)
+        name: orm.Mapped[str] = orm.mapped_column(init=False)
+        children_no_init: orm.Mapped[list["Child"]] = orm.relationship(
+            "Child",
+            uselist=True,
+            init=False,
+        )
+        children_init: orm.Mapped[list["Child"]] = orm.relationship(
+            "Child",
+            uselist=True,
+            overlaps="children_no_init",
+        )
+
+        child_ids: AssociationProxy[list[int]] = association_proxy(
+            "children_init",
+            "id",
+            init=False,
+        )
+
+    class Child(orm.MappedAsDataclass, Base):
+        __tablename__ = "child_with_overridden_type"
+
+        id: orm.Mapped[int] = orm.mapped_column(primary_key=True)
+        model_id: orm.Mapped[int] = orm.mapped_column(ForeignKey(Parent.id))
+
+    class ModelFactory(SQLAlchemyFactory[Parent]):
+        __model__ = Parent
+
+    instance = ModelFactory.build()
+    assert instance.name is None
+    assert instance.children_no_init == []  # type: ignore[unreachable]
+    assert len(instance.children_init) > 0
+    assert instance.child_ids[0] == instance.children_init[0].id