Fix dictionary size change exception when using SQLAlchemy `associati…

…on_proxy` (#624)

* Fix dictionary size change exception when using SQLAlchemy association_proxy

* closes #507

starlette_admin/contrib/sqla/view.py

@@ -95,7 +95,7 @@ def __init__(
         if self.fields is None or len(self.fields) == 0:
             self.fields = [
                 self.model.__dict__[f].key
-                for f in self.model.__dict__
+                for f in list(self.model.__dict__.keys())
                 if type(self.model.__dict__[f]) is InstrumentedAttribute
             ]
         self.fields = (converter or ModelConverter()).convert_fields_list(
@@ -134,7 +134,7 @@ def _setup_primary_key(self) -> None:
             Tuple[InstrumentedAttribute, ...], InstrumentedAttribute
         ] = ()
         self._pk_coerce: Union[Tuple[type, ...], type] = ()
-        for key in self.model.__dict__:
+        for key in list(self.model.__dict__.keys()):
             attr = getattr(self.model, key)
             if isinstance(attr, InstrumentedAttribute) and getattr(
                 attr, "primary_key", False

tests/sqla/test_sync_engine.py

@@ -20,6 +20,7 @@
     select,
 )
 from sqlalchemy.engine import Engine
+from sqlalchemy.ext.associationproxy import association_proxy
 from sqlalchemy.orm import Session, declarative_base, relationship
 from sqlalchemy_file.storage import StorageManager
 from starlette.applications import Starlette
@@ -60,6 +61,8 @@ class User(Base):
     name = Column(String(100), primary_key=True)
     files = Column(sf.FileField(multiple=True))
     products = relationship("Product", back_populates="user")
+    # to reproduce https://github.com/jowilf/starlette-admin/issues/507
+    product_titles = association_proxy("products", "titles")
 
 
 class ProductView(ModelView):