Refactor REST API serializers to avoid circular imports

netbox/extras/api/serializers_/attachments.py

@@ -0,0 +1,50 @@
+from django.core.exceptions import ObjectDoesNotExist
+from drf_spectacular.utils import extend_schema_field
+from rest_framework import serializers
+
+from core.models import ContentType
+from extras.models import ImageAttachment
+from netbox.api.fields import ContentTypeField
+from netbox.api.serializers import ValidatedModelSerializer
+from netbox.constants import NESTED_SERIALIZER_PREFIX
+from utilities.api import get_serializer_for_model
+
+__all__ = (
+    'ImageAttachmentSerializer',
+)
+
+
+class ImageAttachmentSerializer(ValidatedModelSerializer):
+    url = serializers.HyperlinkedIdentityField(view_name='extras-api:imageattachment-detail')
+    content_type = ContentTypeField(
+        queryset=ContentType.objects.all()
+    )
+    parent = serializers.SerializerMethodField(read_only=True)
+
+    class Meta:
+        model = ImageAttachment
+        fields = [
+            'id', 'url', 'display', 'content_type', 'object_id', 'parent', 'name', 'image', 'image_height',
+            'image_width', 'created', 'last_updated',
+        ]
+        brief_fields = ('id', 'url', 'display', 'name', 'image')
+
+    def validate(self, data):
+
+        # Validate that the parent object exists
+        try:
+            data['content_type'].get_object_for_this_type(id=data['object_id'])
+        except ObjectDoesNotExist:
+            raise serializers.ValidationError(
+                "Invalid parent object: {} ID {}".format(data['content_type'], data['object_id'])
+            )
+
+        # Enforce model validation
+        super().validate(data)
+
+        return data
+
+    @extend_schema_field(serializers.JSONField(allow_null=True))
+    def get_parent(self, obj):
+        serializer = get_serializer_for_model(obj.parent, prefix=NESTED_SERIALIZER_PREFIX)
+        return serializer(obj.parent, context={'request': self.context['request']}).data