Simplify EmbeddedModelField transform classes

[timgraham]

No description provided.

[timgraham]

There's a test failure caused by moving this logic here:

======================================================================
ERROR: test_nested_lookup (model_fields_.test_polymorphic_embedded_model_array.QueryingTests.test_nested_lookup)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/tim/code/django-mongodb/tests/model_fields_/test_polymorphic_embedded_model_array.py", line 190, in test_nested_lookup
    Owner.objects.filter(pets__toys__name="")
  File "/home/tim/code/django/django/db/models/manager.py", line 87, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django/django/db/models/query.py", line 1493, in filter
    return self._filter_or_exclude(False, args, kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django/django/db/models/query.py", line 1511, in _filter_or_exclude
    clone._filter_or_exclude_inplace(negate, args, kwargs)
  File "/home/tim/code/django/django/db/models/query.py", line 1518, in _filter_or_exclude_inplace
    self._query.add_q(Q(*args, **kwargs))
  File "/home/tim/code/django/django/db/models/sql/query.py", line 1646, in add_q
    clause, _ = self._add_q(q_object, can_reuse)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django/django/db/models/sql/query.py", line 1678, in _add_q
    child_clause, needed_inner = self.build_filter(
                                 ^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django/django/db/models/sql/query.py", line 1588, in build_filter
    condition = self.build_lookup(lookups, col, value)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django/django/db/models/sql/query.py", line 1409, in build_lookup
    lhs = self.try_transform(lhs, lookup_name)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django/django/db/models/sql/query.py", line 1441, in try_transform
    transform_class = lhs.get_transform(name)
                      ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django-mongodb/django_mongodb_backend/fields/embedded_model_array.py", line 255, in get_transform
    if transform := self._lhs.get_transform(name):
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django/django/db/models/expressions.py", line 406, in get_transform
    return self.output_field.get_transform(name)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/tim/code/django-mongodb/django_mongodb_backend/fields/polymorphic_embedded_model_array.py", line 70, in get_transform
    raise FieldDoesNotExist(
django.core.exceptions.FieldDoesNotExist: The models of field '$item.toys' have no field named 'name'.

It preempts the correct exception from being raised here:

django-mongodb-backend/django_mongodb_backend/fields/embedded_model_array.py

Lines 256 to 258 in e747973

	if transform := self._lhs.get_transform(name):
	if isinstance(transform, KeyTransformFactory):
	raise ValueError("Cannot perform multiple levels of array traversal in a query.")

[WaVEV]

Ok, I think it is a feature, haha 😄 . The field name does not exist in Dog's toy. So it is okey if the test raises.
if we define the Bone as follows

class Bone(EmbeddedModel):
    name = models.CharField(max_length=100, null=True)
    brand = models.CharField(max_length=100)

    def __str__(self):
        return self.brand

the test pass

Or the idea was: I will try to filter whatever it is. If the field isn't there it will match None?

[timgraham]

Thanks. The behavior changed of those error messages changed slightly, but I think it's okay. I added additional tests to demonstrate.