add support for JSONField lookups in an embedded model

django_mongodb_backend/fields/embedded_model.py

@@ -7,6 +7,7 @@
 from django.db.models.lookups import Transform
 
 from .. import forms
+from .json import build_json_mql_path
 
 
 class EmbeddedModelField(models.Field):
@@ -181,18 +182,27 @@ def get_transform(self, name):
         return result
 
     def preprocess_lhs(self, compiler, connection):
-        key_transforms = [self.key_name]
-        previous = self.lhs
+        previous = self
+        embedded_key_transforms = []
+        json_key_transforms = []
         while isinstance(previous, KeyTransform):
-            key_transforms.insert(0, previous.key_name)
+            if isinstance(previous.ref_field, EmbeddedModelField):
+                embedded_key_transforms.insert(0, previous.key_name)
+            else:
+                json_key_transforms.insert(0, previous.key_name)
             previous = previous.lhs
         mql = previous.as_mql(compiler, connection)
-        return mql, key_transforms
+        # The first json_key_transform is the field name.
+        embedded_key_transforms.append(json_key_transforms.pop(0))
+        return mql, embedded_key_transforms, json_key_transforms
 
     def as_mql(self, compiler, connection):
-        mql, key_transforms = self.preprocess_lhs(compiler, connection)
+        mql, key_transforms, json_key_transforms = self.preprocess_lhs(compiler, connection)
         transforms = ".".join(key_transforms)
-        return f"{mql}.{transforms}"
+        result = f"{mql}.{transforms}"
+        if json_key_transforms:
+            result = build_json_mql_path(result, json_key_transforms)
+        return result
 
 
 class KeyTransformFactory:

django_mongodb_backend/fields/json.py

@@ -17,6 +17,26 @@
 from ..query_utils import process_lhs, process_rhs
 
 
+def build_json_mql_path(lhs, key_transforms):
+    # Build the MQL path using the collected key transforms.
+    result = lhs
+    for key in key_transforms:
+        get_field = {"$getField": {"input": result, "field": key}}
+        # Handle array indexing if the key is a digit. If key is something
+        # like '001', it's not an array index despite isdigit() returning True.
+        if key.isdigit() and str(int(key)) == key:
+            result = {
+                "$cond": {
+                    "if": {"$isArray": result},
+                    "then": {"$arrayElemAt": [result, int(key)]},
+                    "else": get_field,
+                }
+            }
+        else:
+            result = get_field
+    return result
+
+
 def contained_by(self, compiler, connection):  # noqa: ARG001
     raise NotSupportedError("contained_by lookup is not supported on this database backend.")
 
@@ -89,23 +109,7 @@ def key_transform(self, compiler, connection):
         key_transforms.insert(0, previous.key_name)
         previous = previous.lhs
     lhs_mql = previous.as_mql(compiler, connection)
-    result = lhs_mql
-    # Build the MQL path using the collected key transforms.
-    for key in key_transforms:
-        get_field = {"$getField": {"input": result, "field": key}}
-        # Handle array indexing if the key is a digit. If key is something
-        # like '001', it's not an array index despite isdigit() returning True.
-        if key.isdigit() and str(int(key)) == key:
-            result = {
-                "$cond": {
-                    "if": {"$isArray": result},
-                    "then": {"$arrayElemAt": [result, int(key)]},
-                    "else": get_field,
-                }
-            }
-        else:
-            result = get_field
-    return result
+    return build_json_mql_path(lhs_mql, key_transforms)
 
 
 def key_transform_in(self, compiler, connection):

tests/model_fields_/models.py

@@ -103,6 +103,7 @@ class Data(EmbeddedModel):
     integer = models.IntegerField(db_column="custom_column")
     auto_now = models.DateTimeField(auto_now=True)
     auto_now_add = models.DateTimeField(auto_now_add=True)
+    json_value = models.JSONField()
 
 
 class Address(EmbeddedModel):

tests/model_fields_/test_embedded_model.py

@@ -114,6 +114,31 @@ def test_order_by_embedded_field(self):
         qs = Holder.objects.filter(data__integer__gt=3).order_by("-data__integer")
         self.assertSequenceEqual(qs, list(reversed(self.objs[4:])))
 
+    def test_embedded_json_field_lookups(self):
+        objs = [
+            Holder.objects.create(
+                data=Data(json_value={"field1": i * 5, "field2": {"0": {"value": list(range(i))}}})
+            )
+            for i in range(4)
+        ]
+        self.assertCountEqual(
+            Holder.objects.filter(data__json_value__field2__0__value__0=0),
+            objs[1:],
+        )
+        self.assertCountEqual(
+            Holder.objects.filter(data__json_value__field2__0__value__1=1),
+            objs[2:],
+        )
+        self.assertCountEqual(Holder.objects.filter(data__json_value__field2__0__value__1=5), [])
+        self.assertCountEqual(Holder.objects.filter(data__json_value__field1__lt=100), objs)
+        self.assertCountEqual(Holder.objects.filter(data__json_value__field1__gt=100), [])
+        self.assertCountEqual(
+            Holder.objects.filter(
+                data__json_value__field1__gte=5, data__json_value__field1__lte=10
+            ),
+            objs[1:3],
+        )
+
     def test_order_and_group_by_embedded_field(self):
         # Create and sort test data by `data__integer`.
         expected_objs = sorted(