Bugfix - Resolve VO class in Lists

If a List field has been declared with content_type as a Value Object and
the value object class was supplied as a string, we should resolve reference
on domain initialization.

src/protean/domain/__init__.py

@@ -30,6 +30,7 @@
     NotSupportedError,
 )
 from protean.fields import HasMany, HasOne, Reference, ValueObject
+from protean.fields import List as ProteanList
 from protean.globals import g
 from protean.reflection import declared_fields, has_fields, id_field
 from protean.utils import (
@@ -510,20 +511,32 @@ def _register_element(self, element_type, element_cls, **opts):  # noqa: C901
         # 1. Associations
         if has_fields(new_cls):
             for _, field_obj in declared_fields(new_cls).items():
+                # Record Association references to resolve later
                 if isinstance(field_obj, (HasOne, HasMany, Reference)) and isinstance(
                     field_obj.to_cls, str
                 ):
                     self._pending_class_resolutions[field_obj.to_cls].append(
                         ("Association", (field_obj, new_cls))
                     )
 
+                # Record Value Object references to resolve later
                 if isinstance(field_obj, ValueObject) and isinstance(
                     field_obj.value_object_cls, str
                 ):
                     self._pending_class_resolutions[field_obj.value_object_cls].append(
                         ("ValueObject", (field_obj, new_cls))
                     )
 
+                # Record Value Object references in List fields to resolve later
+                if (
+                    isinstance(field_obj, ProteanList)
+                    and isinstance(field_obj.content_type, ValueObject)
+                    and isinstance(field_obj.content_type.value_object_cls, str)
+                ):
+                    self._pending_class_resolutions[
+                        field_obj.content_type.value_object_cls
+                    ].append(("ValueObject", (field_obj.content_type, new_cls)))
+
         # 2. Meta Linkages
         if element_type in [
             DomainObjects.ENTITY,

src/protean/fields/embedded.py

@@ -75,7 +75,10 @@ def _validate_value_object_cls(self, value_object_cls):
             raise IncorrectUsageError(
                 {
                     "_value_object": [
-                        f"`{value_object_cls.__name__}` is not a valid Value Object"
+                        (
+                            f"`{value_object_cls.__name__}` is not a valid Value Object "
+                            "and cannot be embedded in a Value Object field"
+                        )
                     ]
                 }
             )

tests/field/test_list.py

@@ -2,8 +2,8 @@
 
 import pytest
 
-from protean import BaseValueObject
-from protean.exceptions import ValidationError
+from protean import BaseAggregate, BaseEntity, BaseValueObject
+from protean.exceptions import IncorrectUsageError, ValidationError
 from protean.fields.basic import (
     Boolean,
     Date,
@@ -15,6 +15,7 @@
     String,
 )
 from protean.fields.embedded import ValueObject
+from protean.reflection import declared_fields
 
 
 class TestListFieldContentType:
@@ -98,6 +99,33 @@ class VO(BaseValueObject):
         value = [VO(foo="bar"), VO(foo="baz")]
         assert field._cast_to_type(value) == value
 
+    def test_list_field_with_invalid_value_object(self):
+        class VO(BaseEntity):
+            foo = String()
+
+        with pytest.raises(IncorrectUsageError) as exc:
+            List(content_type=ValueObject(VO))
+
+        assert exc.value.messages == {
+            "_value_object": [
+                "`VO` is not a valid Value Object and cannot be embedded in "
+                "a Value Object field"
+            ]
+        }
+
+    def test_list_field_with_value_object_string_is_resolved(self, test_domain):
+        class VO(BaseValueObject):
+            foo = String()
+
+        class Foo(BaseAggregate):
+            foos = List(content_type=ValueObject("VO"))
+
+        test_domain.register(VO)
+        test_domain.register(Foo)
+        test_domain.init(traverse=False)
+
+        assert declared_fields(Foo)["foos"].content_type.value_object_cls == VO
+
 
 class TestListFieldAsDictWithDifferentContentTypes:
     def test_list_as_dict_with_string_content_type(self):

tests/field/test_vo.py

@@ -28,5 +28,7 @@ class User(BaseAggregate):
             address = ValueObject(Address)
 
     assert exc.value.messages == {
-        "_value_object": ["`Address` is not a valid Value Object"]
+        "_value_object": [
+            "`Address` is not a valid Value Object and cannot be embedded in a Value Object field"
+        ]
     }

tests/views/test_view_persistence.py

@@ -0,0 +1,44 @@
+import pytest
+
+from protean import BaseView
+from protean.fields import Identifier, Integer, String
+
+
+class Person(BaseView):
+    person_id = Identifier(identifier=True)
+    first_name = String(max_length=50, required=True)
+    last_name = String(max_length=50)
+    age = Integer(default=21)
+
+
+@pytest.fixture(autouse=True)
+def register_elements(test_domain):
+    test_domain.register(Person)
+    test_domain.init(traverse=False)
+
+
+class TestViewPersistence:
+    def test_view_can_be_persisted(self, test_domain):
+        person = Person(person_id="1", first_name="John", last_name="Doe", age=25)
+        test_domain.repository_for(Person).add(person)
+
+        refreshed_person = test_domain.repository_for(Person).get(person.person_id)
+
+        assert refreshed_person.person_id == "1"
+        assert refreshed_person.first_name == "John"
+        assert refreshed_person.last_name == "Doe"
+        assert refreshed_person.age == 25
+
+    def test_view_can_be_updated(self, test_domain):
+        person = Person(person_id="1", first_name="John", last_name="Doe", age=25)
+        test_domain.repository_for(Person).add(person)
+
+        person.first_name = "Jane"
+        test_domain.repository_for(Person).add(person)
+
+        refreshed_person = test_domain.repository_for(Person).get(person.person_id)
+
+        assert refreshed_person.person_id == "1"
+        assert refreshed_person.first_name == "Jane"
+        assert refreshed_person.last_name == "Doe"
+        assert refreshed_person.age == 25

tests/views/tests.py

@@ -127,6 +127,7 @@ def register_elements(test_domain):
     test_domain.register(OrderedPerson, order_by="first_name")
     test_domain.register(OrderedPersonSubclass, order_by="last_name")
     test_domain.register(Building)
+    test_domain.init(traverse=False)
 
 
 class TestViewRegistration: