chore(ruff): Enable RET rules and add explicit fallbacks

Adopt Ruff `RET` to improve return-flow consistency across the codebase.
Simplify control flow by removing redundant `else` blocks after
`return`, and add explicit `return None` (or equivalent) fallbacks
where appropriate to preserve existing behavior.

Fixes #21411

netbox/core/api/schema.py

@@ -39,7 +39,7 @@ class ChoiceFieldFix(OpenApiSerializerFieldExtension):
         if direction == 'request':
             return build_cf
 
-        elif direction == "response":
+        if direction == "response":
             value = build_cf
             label = {
                 **build_basic_type(OpenApiTypes.STR),
@@ -53,6 +53,10 @@ class ChoiceFieldFix(OpenApiSerializerFieldExtension):
                 }
             )
 
+        # TODO: This function should never implicitly/explicitly return `None`
+        # The fallback should be well-defined (drf-spectacular expects request/response naming).
+        return None
+
 
 def viewset_handles_bulk_create(view):
     """Check if view automatically provides list-based bulk create"""
@@ -75,8 +79,7 @@ class NetBoxAutoSchema(AutoSchema):
     def is_bulk_action(self):
         if hasattr(self.view, "action") and self.view.action in BULK_ACTIONS:
             return True
-        else:
-            return False
+        return False
 
     def get_operation_id(self):
         """
@@ -316,8 +319,7 @@ class FixSerializedPKRelatedField(OpenApiSerializerFieldExtension):
         if direction == "response":
             component = auto_schema.resolve_serializer(self.target.serializer, direction)
             return component.ref if component else None
-        else:
-            return build_basic_type(OpenApiTypes.INT)
+        return build_basic_type(OpenApiTypes.INT)
 
 
 class FixIntegerRangeSerializerSchema(OpenApiSerializerExtension):

netbox/core/api/serializers_/object_types.py

@@ -34,14 +34,14 @@ class ObjectTypeSerializer(BaseModelSerializer):
     @extend_schema_field(OpenApiTypes.STR)
     def get_rest_api_endpoint(self, obj):
         if not (model := obj.model_class()):
-            return
+            return None
         try:
             return get_action_url(model, action='list', rest_api=True)
         except NoReverseMatch:
-            return
+            return None
 
     @extend_schema_field(OpenApiTypes.STR)
     def get_description(self, obj):
         if not (model := obj.model_class()):
-            return
+            return None
         return inspect.getdoc(model)

netbox/core/api/views.py

@@ -285,5 +285,4 @@ class BackgroundTaskViewSet(BaseRQViewSet):
         stopped_jobs = stop_rq_job(id)
         if len(stopped_jobs) == 1:
             return HttpResponse(status=200)
-        else:
-            return HttpResponse(status=204)
+        return HttpResponse(status=204)

netbox/core/management/commands/nbshell.py

@@ -144,7 +144,7 @@ class Command(BaseCommand):
         # If Python code has been passed, execute it and exit.
         if options['command']:
             exec(options['command'], namespace)
-            return
+            return None
 
         # Try to enable tab-complete
         try:

netbox/core/models/data.py

@@ -98,6 +98,7 @@ class DataSource(JobsMixin, PrimaryModel):
     def get_type_display(self):
         if backend := registry['data_backends'].get(self.type):
             return backend.label
+        return None
 
     def get_status_color(self):
         return DataSourceStatusChoices.colors.get(self.status)

netbox/core/models/files.py

@@ -79,8 +79,7 @@ class ManagedFile(SyncedDataMixin, models.Model):
                 'scripts': settings.SCRIPTS_ROOT,
                 'reports': settings.REPORTS_ROOT,
             }[self.file_root]
-        else:
-            return ""
+        return ""
 
     def sync_data(self):
         if self.data_file:

netbox/core/models/jobs.py

@@ -146,7 +146,7 @@ class Job(models.Model):
         if self.object_type:
             if self.object_type.model == 'reportmodule':
                 return reverse('extras:report_result', kwargs={'job_pk': self.pk})
-            elif self.object_type.model == 'scriptmodule':
+            if self.object_type.model == 'scriptmodule':
                 return reverse('extras:script_result', kwargs={'job_pk': self.pk})
         return reverse('core:job', args=[self.pk])
 

netbox/core/models/object_types.py

@@ -218,19 +218,22 @@ class ObjectType(ContentType):
     def app_verbose_name(self):
         if model := self.model_class():
             return model._meta.app_config.verbose_name
+        return None
 
     @property
     def model_verbose_name(self):
         if model := self.model_class():
             return model._meta.verbose_name
+        return None
 
     @property
     def model_verbose_name_plural(self):
         if model := self.model_class():
             return model._meta.verbose_name_plural
+        return None
 
     @property
     def is_plugin_model(self):
         if not (model := self.model_class()):
-            return  # Return null if model class is invalid
+            return None  # Return null if model class is invalid
         return isinstance(model._meta.app_config, PluginConfig)