fix: create_schema crashes on models with a ForeignObject reverse relation

ninja/orm/factory.py

@@ -1,8 +1,8 @@
 import itertools
-from typing import Any, Dict, Iterator, List, Optional, Set, Tuple, Type, Union, cast
+from typing import Any, Dict, Iterator, List, Optional, Set, Tuple, Type, Union
 
 from django.db.models import Field as DjangoField
-from django.db.models import ManyToManyRel, ManyToOneRel, Model
+from django.db.models import ForeignObjectRel, Model
 from pydantic import create_model as create_pydantic_model
 
 from ninja.errors import ConfigError
@@ -158,10 +158,11 @@ def _selected_model_fields(
     def _model_fields(self, model: Type[Model]) -> Iterator[DjangoField]:
         "returns iterator with all the fields that can be part of schema"
         for fld in model._meta.get_fields():
-            if isinstance(fld, (ManyToOneRel, ManyToManyRel)):
-                # skipping relations
+            if isinstance(fld, ForeignObjectRel):
+                # skipping reverse relations (ManyToOneRel, ManyToManyRel, and the
+                # bare ForeignObjectRel produced by a ForeignObject field)
                 continue
-            yield cast(DjangoField, fld)
+            yield fld
 
 
 factory = SchemaFactory()

tests/test_orm_relations.py

@@ -1,4 +1,5 @@
 from django.db import models
+from django.test.utils import isolate_apps
 
 from ninja import NinjaAPI
 from ninja.orm import create_schema
@@ -35,3 +36,34 @@ def post_with_m2m(request, payload: WithM2MSchema):
     response = client.post("/bar", json={"m2m": []})
     assert response.status_code == 200, str(response.json())
     assert response.json() == {"m2m": []}
+
+
+@isolate_apps("tests")
+def test_reverse_foreign_object_relation_is_skipped():
+    """A ForeignObject's reverse accessor is a bare ForeignObjectRel. Building a
+    schema for the referenced model must skip it like any other reverse relation
+    instead of crashing on the missing ``help_text`` attribute (see #1530)."""
+
+    class Order(models.Model):
+        class Meta:
+            app_label = "tests"
+
+    class OrderDetail(models.Model):
+        order_id = models.PositiveIntegerField()
+        order = models.ForeignObject(
+            Order,
+            on_delete=models.CASCADE,
+            from_fields=["order_id"],
+            to_fields=["id"],
+            related_name="details",
+        )
+
+        class Meta:
+            app_label = "tests"
+
+    # Order gets a reverse ForeignObjectRel "details"; schema generation must not raise.
+    OrderSchema = create_schema(Order)
+
+    # The reverse relation is skipped, so it does not appear as a schema field.
+    assert "details" not in OrderSchema.model_fields
+    assert "id" in OrderSchema.model_fields