fix: assign fallback tenant during imports

netbox_export/services/plugin_compat.py

@@ -1,5 +1,12 @@
 from __future__ import annotations
 
+from django.apps import apps
+from django.core.exceptions import FieldDoesNotExist, ValidationError
+
+AUTO_IMPORT_TENANT_NAME = "Auto-Import"
+AUTO_IMPORT_TENANT_SLUG = "auto-import"
+MISSING_TENANT_MESSAGE = "Für dieses Objekt muss ein Mandant angegeben werden."
+
 
 def netbox_utilities_tenant_required() -> bool:
     """Return the effective tenant policy without requiring the optional plugin."""
@@ -10,8 +17,89 @@ def netbox_utilities_tenant_required() -> bool:
     return bool(tenant_required())
 
 
-def relation_required_before_save(field, *, tenant_required: bool) -> bool:
-    if not tenant_required or field.name != "tenant":
+def is_tenant_relation(field) -> bool:
+    if field.name != "tenant":
         return False
     related_model = getattr(field.remote_field, "model", None)
     return getattr(getattr(related_model, "_meta", None), "label_lower", None) == "tenancy.tenant"
+
+
+class PluginCompatibility:
+    def __init__(
+        self,
+        warnings,
+        *,
+        dry_run: bool,
+        tenant_required: bool | None = None,
+        tenant_model_loader=None,
+    ):
+        self.warnings = warnings
+        self.dry_run = dry_run
+        self.tenant_required = (
+            netbox_utilities_tenant_required() if tenant_required is None else tenant_required
+        )
+        self.tenant_model_loader = tenant_model_loader or (lambda: apps.get_model("tenancy.tenant"))
+        self._fallback_tenant = None
+
+    @staticmethod
+    def _supports_tenant(obj) -> bool:
+        try:
+            field = obj._meta.get_field("tenant")
+        except FieldDoesNotExist:
+            return False
+        return is_tenant_relation(field)
+
+    @staticmethod
+    def _is_missing_tenant_error(exc: ValidationError) -> bool:
+        return MISSING_TENANT_MESSAGE in exc.messages
+
+    def _auto_import_tenant(self):
+        if self._fallback_tenant is not None:
+            return self._fallback_tenant
+
+        model = self.tenant_model_loader()
+        tenant = model._default_manager.filter(name=AUTO_IMPORT_TENANT_NAME).order_by("pk").first()
+        created = tenant is None
+        if tenant is None:
+            slug = AUTO_IMPORT_TENANT_SLUG
+            suffix = 2
+            while model._default_manager.filter(slug=slug).exists():
+                slug = f"{AUTO_IMPORT_TENANT_SLUG}-{suffix}"
+                suffix += 1
+            tenant = model._default_manager.create(name=AUTO_IMPORT_TENANT_NAME, slug=slug)
+
+        if self.dry_run:
+            message = (
+                'Für den Prüflauf wurde der Mandant "Auto-Import" automatisch als Ersatzmandant '
+                "verwendet; er wird nicht dauerhaft angelegt oder geändert."
+            )
+        elif created:
+            message = (
+                'Der Mandant "Auto-Import" wurde automatisch erstellt und Objekten ohne '
+                "auflösbaren Mandanten zugewiesen."
+            )
+        else:
+            message = (
+                'Der vorhandene Mandant "Auto-Import" wurde automatisch für Objekte ohne '
+                "auflösbaren Mandanten ausgewählt."
+            )
+        self.warnings.append(message)
+        self._fallback_tenant = tenant
+        return tenant
+
+    def _assign_fallback_tenant(self, obj, *, force: bool = False) -> bool:
+        if getattr(obj, "tenant_id", None) is not None or not self._supports_tenant(obj):
+            return False
+        if not force and not self.tenant_required:
+            return False
+        obj.tenant = self._auto_import_tenant()
+        return True
+
+    def save(self, obj, **kwargs):
+        self._assign_fallback_tenant(obj)
+        try:
+            return obj.save(**kwargs)
+        except ValidationError as exc:
+            if not self._is_missing_tenant_error(exc) or not self._assign_fallback_tenant(obj, force=True):
+                raise
+            return obj.save(**kwargs)