415 Auto-add reference fields in child entities

This commit includes changes that add a `Reference` field in the enclosed
child entity pointing to the aggregate, when an explicit reference has
not been provided.

src/protean/container.py

@@ -399,10 +399,14 @@ def __create_id_field(new_class):
         id_field = Auto(identifier=True)
 
         setattr(new_class, "id", id_field)
+
+        # Set the name of the field on itself
         id_field.__set_name__(new_class, "id")
 
+        # Set the name of the attribute on the class
         setattr(new_class, _ID_FIELD_NAME, id_field.field_name)
 
+        # Add the attribute to _FIELDS for introspection
         field_objects = getattr(new_class, _FIELDS)
         field_objects["id"] = id_field
         setattr(new_class, _FIELDS, field_objects)

src/protean/core/entity.py

@@ -10,7 +10,7 @@
 from protean.exceptions import IncorrectUsageError, NotSupportedError, ValidationError
 from protean.fields import Auto, HasMany, Reference, ValueObject
 from protean.fields.association import Association
-from protean.reflection import attributes, declared_fields, fields, id_field
+from protean.reflection import attributes, declared_fields, fields, id_field, _FIELDS
 from protean.utils import (
     DomainObjects,
     derive_element_class,
@@ -111,19 +111,6 @@ class User(BaseEntity):
     class Meta:
         abstract = True
 
-    def __init_subclass__(subclass) -> None:
-        super().__init_subclass__()
-
-        subclass.__set_up_reference_fields()
-
-    @classmethod
-    def __set_up_reference_fields(subclass):
-        """Walk through relation fields and setup shadow attributes"""
-        for _, field in declared_fields(subclass).items():
-            if isinstance(field, Reference):
-                shadow_field_name, shadow_field = field.get_shadow_field()
-                shadow_field.__set_name__(subclass, shadow_field_name)
-
     def __init__(self, *template, **kwargs):  # noqa: C901
         """
         Initialise the entity object.
@@ -462,4 +449,42 @@ def entity_factory(element_cls, **kwargs):
             }
         )
 
+    # Set up reference fields
+    if not element_cls.meta_.abstract:
+        reference_field = None
+        for field_obj in declared_fields(element_cls).values():
+            if isinstance(field_obj, Reference):
+                # An explicit `Reference` field is already present
+                reference_field = field_obj
+                break
+
+        if reference_field is None:
+            # If no explicit Reference field is present, create one
+            reference_field = Reference(element_cls.meta_.aggregate_cls)
+
+            # If aggregate_cls is a string, set field name to inflection.underscore(aggregate_cls)
+            #   Else, if it is a class, extract class name and set field name to inflection.underscore(class_name)
+            if isinstance(element_cls.meta_.aggregate_cls, str):
+                field_name = inflection.underscore(element_cls.meta_.aggregate_cls)
+            else:
+                field_name = inflection.underscore(
+                    element_cls.meta_.aggregate_cls.__name__
+                )
+
+            setattr(element_cls, field_name, reference_field)
+
+            # Set the name of the field on itself
+            reference_field.__set_name__(element_cls, field_name)
+
+            # FIXME Centralize this logic to add fields dynamically to _FIELDS
+            field_objects = getattr(element_cls, _FIELDS)
+            field_objects[field_name] = reference_field
+            setattr(element_cls, _FIELDS, field_objects)
+
+        # Set up shadow fields for Reference fields
+        for _, field in fields(element_cls).items():
+            if isinstance(field, Reference):
+                shadow_field_name, shadow_field = field.get_shadow_field()
+                shadow_field.__set_name__(element_cls, shadow_field_name)
+
     return element_cls

tests/entity/elements.py

@@ -1,10 +1,14 @@
 from collections import defaultdict
 from enum import Enum
 
-from protean import BaseEntity
+from protean import BaseAggregate, BaseEntity
 from protean.fields import Auto, HasOne, Integer, String
 
 
+class Account(BaseAggregate):
+    account_number = String(max_length=50, required=True)
+
+
 class AbstractPerson(BaseEntity):
     age = Integer(default=5)
 
@@ -16,46 +20,65 @@ class ConcretePerson(BaseEntity):
     first_name = String(max_length=50, required=True)
     last_name = String(max_length=50)
 
+    class Meta:
+        aggregate_cls = "Account"
+
 
 class Person(BaseEntity):
     first_name = String(max_length=50, required=True)
     last_name = String(max_length=50)
     age = Integer(default=21)
 
+    class Meta:
+        aggregate_cls = "Account"
+
 
 class PersonAutoSSN(BaseEntity):
     ssn = Auto(identifier=True)
     first_name = String(max_length=50, required=True)
     last_name = String(max_length=50)
     age = Integer(default=21)
 
+    class Meta:
+        aggregate_cls = "Account"
+
 
 class PersonExplicitID(BaseEntity):
     ssn = String(max_length=36, identifier=True)
     first_name = String(max_length=50, required=True)
     last_name = String(max_length=50)
     age = Integer(default=21)
 
+    class Meta:
+        aggregate_cls = "Account"
+
 
 class Relative(BaseEntity):
     first_name = String(max_length=50, required=True)
     last_name = String(max_length=50)
     age = Integer(default=21)
     relative_of = HasOne(Person)
 
+    class Meta:
+        aggregate_cls = "Account"
+
 
 class Adult(Person):
     pass
 
     class Meta:
         schema_name = "adults"
+        aggregate_cls = "Account"
 
 
 class NotAPerson(BaseEntity):
     first_name = String(max_length=50, required=True)
     last_name = String(max_length=50)
     age = Integer(default=21)
 
+    class Meta:
+        aggregate_cls = "Account"
+
 
 # Entities to test Meta Info overriding # START #
 class DbPerson(BaseEntity):
@@ -65,21 +88,25 @@ class DbPerson(BaseEntity):
 
     class Meta:
         schema_name = "pepes"
+        aggregate_cls = "Account"
 
 
 class SqlPerson(Person):
     class Meta:
         schema_name = "people"
+        aggregate_cls = "Account"
 
 
 class DifferentDbPerson(Person):
     class Meta:
         provider = "non-default"
+        aggregate_cls = "Account"
 
 
 class SqlDifferentDbPerson(Person):
     class Meta:
         provider = "non-default-sql"
+        aggregate_cls = "Account"
 
 
 class OrderedPerson(BaseEntity):
@@ -89,23 +116,32 @@ class OrderedPerson(BaseEntity):
 
     class Meta:
         order_by = "first_name"
+        aggregate_cls = "Account"
 
 
 class OrderedPersonSubclass(Person):
     class Meta:
         order_by = "last_name"
+        aggregate_cls = "Account"
 
 
 class BuildingStatus(Enum):
     WIP = "WIP"
     DONE = "DONE"
 
 
+class Area(BaseAggregate):
+    name = String(max_length=50)
+
+
 class Building(BaseEntity):
     name = String(max_length=50)
     floors = Integer()
     status = String(choices=BuildingStatus)
 
+    class Meta:
+        aggregate_cls = "Area"
+
     def defaults(self):
         if not self.status:
             if self.floors == 4:

tests/entity/test_entity.py

@@ -1,125 +1,19 @@
-from collections import defaultdict
-from enum import Enum
-
-from protean import BaseEntity
 from protean.container import Options
-from protean.fields import Auto, HasOne, Integer, String
+from protean.fields import Auto, Integer, String
 from protean.reflection import attributes, declared_fields
 
-
-class AbstractPerson(BaseEntity):
-    age = Integer(default=5)
-
-    class Meta:
-        abstract = True
-
-
-class ConcretePerson(BaseEntity):
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-
-
-class Person(BaseEntity):
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-    age = Integer(default=21)
-
-
-class PersonAutoSSN(BaseEntity):
-    ssn = Auto(identifier=True)
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-    age = Integer(default=21)
-
-
-class PersonExplicitID(BaseEntity):
-    ssn = String(max_length=36, identifier=True)
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-    age = Integer(default=21)
-
-
-class Relative(BaseEntity):
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-    age = Integer(default=21)
-    relative_of = HasOne(Person)
-
-
-class Adult(Person):
-    class Meta:
-        schema_name = "adults"
-
-
-class NotAPerson(BaseEntity):
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-    age = Integer(default=21)
-
-
-# Entities to test Meta Info overriding # START #
-class DbPerson(BaseEntity):
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-    age = Integer(default=21)
-
-    class Meta:
-        schema_name = "pepes"
-
-
-class SqlPerson(Person):
-    class Meta:
-        schema_name = "people"
-
-
-class DifferentDbPerson(Person):
-    class Meta:
-        provider = "non-default"
-
-
-class SqlDifferentDbPerson(Person):
-    class Meta:
-        provider = "non-default-sql"
-
-
-class OrderedPerson(BaseEntity):
-    first_name = String(max_length=50, required=True)
-    last_name = String(max_length=50)
-    age = Integer(default=21)
-
-    class Meta:
-        order_by = "first_name"
-
-
-class OrderedPersonSubclass(Person):
-    class Meta:
-        order_by = "last_name"
-
-
-class BuildingStatus(Enum):
-    WIP = "WIP"
-    DONE = "DONE"
-
-
-class Building(BaseEntity):
-    name = String(max_length=50)
-    floors = Integer()
-    status = String(choices=BuildingStatus)
-
-    def defaults(self):
-        if not self.status:
-            if self.floors == 4:
-                self.status = BuildingStatus.DONE.value
-            else:
-                self.status = BuildingStatus.WIP.value
-
-    def clean(self):
-        errors = defaultdict(list)
-
-        if self.floors >= 4 and self.status != BuildingStatus.DONE.value:
-            errors["status"].append("should be DONE")
-
-        return errors
+from .elements import (
+    AbstractPerson,
+    ConcretePerson,
+    Person,
+    PersonAutoSSN,
+    Relative,
+    SqlDifferentDbPerson,
+    SqlPerson,
+    DbPerson,
+    DifferentDbPerson,
+    Adult,
+)
 
 
 class TestEntityMeta: