Simplify and rename EmbeddedModelArrayField's transform classes

Author: timgraham

django_mongodb_backend/fields/embedded_model_array.py

@@ -67,7 +67,8 @@ def get_transform(self, name):
         transform = super().get_transform(name)
         if transform:
             return transform
-        return KeyTransformFactory(name, self)
+        field = self.base_field.embedded_model._meta.get_field(name)
+        return EmbeddedModelArrayFieldTransformFactory(field)
 
     def _get_lookup(self, lookup_name):
         lookup = super()._get_lookup(lookup_name)
@@ -223,17 +224,15 @@ class EmbeddedModelArrayFieldLessThanOrEqual(
     pass
 
 
-class KeyTransform(Transform):
+class EmbeddedModelArrayFieldTransform(Transform):
     field_class_name = "EmbeddedModelArrayField"
 
-    def __init__(self, key_name, array_field, *args, **kwargs):
+    def __init__(self, field, *args, **kwargs):
         super().__init__(*args, **kwargs)
-        self.array_field = array_field
-        self.key_name = key_name
         # Lookups iterate over the array of embedded models. A virtual column
         # of the queried field's type represents each element.
-        column_target = array_field.base_field.embedded_model._meta.get_field(key_name).clone()
-        column_name = f"$item.{key_name}"
+        column_target = field.clone()
+        column_name = f"$item.{field.column}"
         column_target.db_column = column_name
         column_target.set_attributes_from_name(column_name)
         self._lhs = Col(None, column_target)
@@ -254,7 +253,7 @@ def get_transform(self, name):
         # Once the sub-lhs is a transform, all the filters are applied over it.
         # Otherwise get the transform from the nested embedded model field.
         if transform := self._lhs.get_transform(name):
-            if isinstance(transform, KeyTransformFactory):
+            if isinstance(transform, EmbeddedModelArrayFieldTransformFactory):
                 raise ValueError("Cannot perform multiple levels of array traversal in a query.")
             self._sub_transform = transform
             return self
@@ -296,10 +295,9 @@ def output_field(self):
         return _EmbeddedModelArrayOutputField(self._lhs.output_field)
 
 
-class KeyTransformFactory:
-    def __init__(self, key_name, base_field):
-        self.key_name = key_name
-        self.base_field = base_field
+class EmbeddedModelArrayFieldTransformFactory:
+    def __init__(self, field):
+        self.field = field
 
     def __call__(self, *args, **kwargs):
-        return KeyTransform(self.key_name, self.base_field, *args, **kwargs)
+        return EmbeddedModelArrayFieldTransform(self.field, *args, **kwargs)

django_mongodb_backend/fields/polymorphic_embedded_model_array.py

@@ -7,8 +7,10 @@
 
 from . import PolymorphicEmbeddedModelField
 from .array import ArrayField, ArrayLenTransform
-from .embedded_model_array import KeyTransform as ArrayFieldKeyTransform
-from .embedded_model_array import KeyTransformFactory as ArrayFieldKeyTransformFactory
+from .embedded_model_array import (
+    EmbeddedModelArrayFieldTransform,
+    EmbeddedModelArrayFieldTransformFactory,
+)
 
 
 class PolymorphicEmbeddedModelArrayField(ArrayField):
@@ -62,7 +64,15 @@ def get_transform(self, name):
         transform = super().get_transform(name)
         if transform:
             return transform
-        return KeyTransformFactory(name, self)
+        for model in self.base_field.embedded_models:
+            with contextlib.suppress(FieldDoesNotExist):
+                field = model._meta.get_field(name)
+                break
+        else:
+            raise FieldDoesNotExist(
+                f"The models of field '{self.name}' have no field named '{name}'."
+            )
+        return PolymorphicArrayFieldTransformFactory(field)
 
     def _get_lookup(self, lookup_name):
         lookup = super()._get_lookup(lookup_name)
@@ -79,32 +89,23 @@ def as_mql(self, compiler, connection):
         return EmbeddedModelArrayFieldLookups
 
 
-class KeyTransform(ArrayFieldKeyTransform):
+class PolymorphicArrayFieldTransform(EmbeddedModelArrayFieldTransform):
     field_class_name = "PolymorphicEmbeddedModelArrayField"
 
-    def __init__(self, key_name, array_field, *args, **kwargs):
-        # Skip ArrayFieldKeyTransform.__init__()
+    def __init__(self, field, *args, **kwargs):
+        # Skip EmbeddedModelArrayFieldTransform.__init__()
         Transform.__init__(self, *args, **kwargs)
-        self.array_field = array_field
-        self.key_name = key_name
-        for model in array_field.base_field.embedded_models:
-            with contextlib.suppress(FieldDoesNotExist):
-                field = model._meta.get_field(key_name)
-                break
-        else:
-            raise FieldDoesNotExist(
-                f"The models of field '{array_field.name}' have no field named '{key_name}'."
-            )
         # Lookups iterate over the array of embedded models. A virtual column
         # of the queried field's type represents each element.
         column_target = field.clone()
-        column_name = f"$item.{key_name}"
+        column_name = f"$item.{field.column}"
+        column_target.name = f"{field.name}"
         column_target.db_column = column_name
         column_target.set_attributes_from_name(column_name)
         self._lhs = Col(None, column_target)
         self._sub_transform = None
 
 
-class KeyTransformFactory(ArrayFieldKeyTransformFactory):
+class PolymorphicArrayFieldTransformFactory(EmbeddedModelArrayFieldTransformFactory):
     def __call__(self, *args, **kwargs):
-        return KeyTransform(self.key_name, self.base_field, *args, **kwargs)
+        return PolymorphicArrayFieldTransform(self.field, *args, **kwargs)

tests/model_fields_/test_embedded_model_array.py

@@ -283,8 +283,8 @@ def test_invalid_field(self):
             Exhibit.objects.filter(sections__section__in=[10]).first()
 
     def test_invalid_nested_field(self):
-        msg = "Cannot perform multiple levels of array traversal in a query."
-        with self.assertRaisesMessage(ValueError, msg):
+        msg = "Artifact has no field named 'xx'"
+        with self.assertRaisesMessage(FieldDoesNotExist, msg):
             Exhibit.objects.filter(sections__artifacts__xx=10).first()
 
     def test_invalid_lookup(self):

tests/model_fields_/test_polymorphic_embedded_model_array.py

@@ -177,8 +177,8 @@ def test_invalid_field(self):
             Owner.objects.filter(pets__xxx=10).first()
 
     def test_invalid_nested_field(self):
-        msg = "Cannot perform multiple levels of array traversal in a query."
-        with self.assertRaisesMessage(ValueError, msg):
+        msg = "The models of field 'toys' have no field named 'xxx'."
+        with self.assertRaisesMessage(FieldDoesNotExist, msg):
             Owner.objects.filter(pets__toys__xxx=10).first()
 
     def test_invalid_lookup(self):