Add support for sqlalchemy collection_class property (#625)

* Add support for sqlalchemy collection_class property

* fix ci

Author: jowilf

starlette_admin/contrib/sqla/converters.py

@@ -106,7 +106,13 @@ def convert_fields_list(
                     ):
                         converted_fields.append(HasOne(attr.key, identity=identity))
                     else:
-                        converted_fields.append(HasMany(attr.key, identity=identity))
+                        converted_fields.append(
+                            HasMany(
+                                attr.key,
+                                identity=identity,
+                                collection_class=attr.collection_class or list,
+                            )
+                        )
                 elif isinstance(attr, ColumnProperty):
                     assert (
                         len(attr.columns) == 1

starlette_admin/contrib/sqla/view.py

@@ -14,7 +14,7 @@
 from sqlalchemy.sql import Select
 from starlette.requests import Request
 from starlette.responses import Response
-from starlette_admin import BaseField
+from starlette_admin import BaseField, HasMany
 from starlette_admin._types import RequestAction
 from starlette_admin.contrib.sqla.converters import (
     BaseSQLAModelConverter,
@@ -521,12 +521,10 @@ async def _arrange_data(
         for field in self.get_fields_list(request, request.state.action):
             if isinstance(field, RelationField) and data[field.name] is not None:
                 foreign_model = self._find_foreign_model(field.identity)  # type: ignore
-                if not field.multiple:
-                    arranged_data[field.name] = await foreign_model.find_by_pk(
-                        request, data[field.name]
-                    )
+                if isinstance(field, HasMany):
+                    arranged_data[field.name] = field.collection_class(await foreign_model.find_by_pks(request, data[field.name]))  # type: ignore[call-arg]
                 else:
-                    arranged_data[field.name] = await foreign_model.find_by_pks(
+                    arranged_data[field.name] = await foreign_model.find_by_pk(
                         request, data[field.name]
                     )
             else:

starlette_admin/fields.py

@@ -9,6 +9,7 @@
 from typing import (
     Any,
     Callable,
+    Collection,
     Dict,
     List,
     Optional,
@@ -1094,6 +1095,7 @@ class HasMany(RelationField):
     """A field representing a "has-many" relationship between two models."""
 
     multiple: bool = True
+    collection_class: Union[Type[Collection[Any]], Callable[[], Collection[Any]]] = list
 
 
 @dataclass(init=False)

tests/sqla/test_sqla_and_pydantic.py

@@ -38,7 +38,7 @@ class User(Base, IDMixin):
 
     name = Column(String(100))
 
-    todos = relationship("Todo", back_populates="user")
+    todos = relationship("Todo", back_populates="user", collection_class=set)
 
 
 class Todo(Base, IDMixin):