fix: tolerate missing external import references

README.md

@@ -92,8 +92,10 @@ Import werden vorhandene Objekte über ihre eindeutigen Fachschlüssel erkannt.
 ## Verhalten und Grenzen
 
 - Quelle und Ziel müssen NetBox 4.6.x und dieselben Plugins/Modelle verwenden.
-- Benutzerkonten und Berechtigungen werden nicht exportiert. Referenzen auf
+- Benutzerkonten und Berechtigungen werden nicht exportiert. Fehlende oder
-  Benutzer oder Gruppen müssen auf dem Ziel bereits eindeutig vorhanden sein.
+  nicht eindeutige Referenzen auf Benutzer und Gruppen werden ausgelassen und
+  nach dem Import als Warnung angezeigt. Benötigt ein neuer Datensatz zwingend
+  eine solche Referenz, wird nur dieser Datensatz übersprungen.
 - Der Import erstellt und aktualisiert Objekte. Zielobjekte, die im Archiv nicht
   vorkommen, werden bewusst nicht gelöscht.
 - Fehlende Bilddateien werden im Archiv vermerkt, können aber nicht rekonstruiert

netbox_export/__init__.py

@@ -7,7 +7,7 @@ class NetBoxExportConfig(PluginConfig):
     name = "netbox_export"
     verbose_name = "NetBox-Export"
     description = "Portable ZIP export and import for tenants and locations"
-    version = "0.3.0"
+    version = "0.3.1"
     author = "NetBox Export contributors"
     base_url = "netbox-export"
     min_version = "4.6.0"

netbox_export/services/exporter.py

@@ -39,7 +39,7 @@ def export_scope(
         "created_at": datetime.now(UTC).isoformat(),
         "source_instance": str(InstanceIdentity.local_id()),
         "source_netbox_version": getattr(getattr(settings, "RELEASE", None), "version", "4.6"),
-        "plugin_version": "0.3.0",
+        "plugin_version": "0.3.1",
         "scope": {
             "type": scope_type,
             "source_pk": str(scope_id),

netbox_export/services/importer.py

@@ -16,6 +16,7 @@ from netbox_export.models import ImportedObjectMapping
 from .archive import ParsedArchive
 from .codec import SKIP_FIELD_NAMES, decode_scalar, generic_foreign_keys
 from .exceptions import ArchiveValidationError, ExportImportError, ImportConflictError
+from .references import MISSING_REFERENCE, ReferenceResolver
 
 EXPLICIT_IDENTITIES = {
     "tenancy.tenantgroup": ("slug",),
@@ -76,48 +77,27 @@ def _model_for(label: str):
     return model
 
 
-def _external_object(spec: dict):
+def _decode_archived_value(encoded, resolver):
-    model = _model_for(spec["model"])
-    lookup = {key: decode_scalar(value) for key, value in spec.get("lookup", {}).items()}
-    try:
-        return model._default_manager.get(**lookup)
-    except model.DoesNotExist as exc:
-        raise ArchiveValidationError(
-            f"Externe Referenz fehlt: {spec['model']} mit {lookup}."
-        ) from exc
-    except model.MultipleObjectsReturned as exc:
-        raise ArchiveValidationError(
-            f"Externe Referenz ist nicht eindeutig: {spec['model']} mit {lookup}."
-        ) from exc
-
-
-def _resolve_reference(spec, resolved: dict[str, models.Model]):
-    if spec is None:
-        return None, True
-    if "ref" in spec:
-        return resolved.get(spec["ref"]), spec["ref"] in resolved
-    if "external" in spec:
-        return _external_object(spec["external"]), True
-    raise ArchiveValidationError("Eine Objektreferenz im Archiv ist ungültig.")
-
-
-def _decode_archived_value(encoded, resolved):
     if isinstance(encoded, dict) and encoded.get("$type") == "object_ref":
-        target, available = _resolve_reference(encoded.get("value"), resolved)
+        target, available = resolver.resolve(encoded.get("value"))
+        if target is MISSING_REFERENCE:
+            return None, True
         return (target.pk if available and target is not None else None), available
     if isinstance(encoded, dict) and encoded.get("$type") == "multiobject_ref":
         values = []
         for spec in encoded.get("value", []):
-            target, available = _resolve_reference(spec, resolved)
+            target, available = resolver.resolve(spec)
             if not available:
                 return None, False
+            if target is MISSING_REFERENCE:
+                continue
             values.append(target.pk)
         return values, True
     if isinstance(encoded, dict) and "$type" not in encoded:
         value = {}
         all_available = True
         for key, item in encoded.items():
-            decoded, available = _decode_archived_value(item, resolved)
+            decoded, available = _decode_archived_value(item, resolver)
             value[key] = decoded
             all_available &= available
         return value, all_available
@@ -138,7 +118,7 @@ def _identity_candidates(model):
             yield tuple(constraint.fields)
 
 
-def _identity_lookup(model, record, resolved):
+def _identity_lookup(model, record, resolver):
     scalar_values = record.get("fields", {})
     relation_values = record.get("relations", {})
     generic_values = record.get("generic_relations", {})
@@ -156,14 +136,20 @@ def _identity_lookup(model, record, resolved):
             if name in scalar_values:
                 value = decode_scalar(scalar_values[name])
             elif name in relation_values:
-                value, available = _resolve_reference(relation_values[name], resolved)
+                value, available = resolver.resolve(relation_values[name])
                 if not available:
                     raise IdentityNotReady
+                if value is MISSING_REFERENCE:
+                    usable = False
+                    break
             elif name in generic_storage:
                 value_type, spec = generic_storage[name]
-                target, available = _resolve_reference(spec, resolved)
+                target, available = resolver.resolve(spec)
                 if not available:
                     raise IdentityNotReady
+                if target is MISSING_REFERENCE:
+                    usable = False
+                    break
                 if target is None:
                     value = None
                 elif value_type == "content_type":
@@ -197,11 +183,11 @@ def _mapped_object(source_instance: uuid.UUID, record: dict, model):
         return None
 
 
-def _find_existing(source_instance, model, record, resolved):
+def _find_existing(source_instance, model, record, resolver):
     mapped = _mapped_object(source_instance, record, model)
     if mapped is not None:
         return mapped
-    lookup = _identity_lookup(model, record, resolved)
+    lookup = _identity_lookup(model, record, resolver)
     if not lookup:
         return None
     try:
@@ -224,11 +210,12 @@ def _write_mapping(source_instance, record, obj):
     )
 
 
-def _field_kwargs(model, record, resolved):
+def _field_kwargs(model, record, resolver):
     valid_fields = {field.name: field for field in model._meta.concrete_fields}
     kwargs = {}
     unresolved = []
     unresolved_values = []
+    missing_required = []
     for name, encoded in record.get("fields", {}).items():
         field = valid_fields.get(name)
         if (
@@ -241,51 +228,59 @@ def _field_kwargs(model, record, resolved):
             continue
         if isinstance(field, (models.ForeignKey, models.OneToOneField)):
             continue
-        value, available = _decode_archived_value(encoded, resolved)
+        value, available = _decode_archived_value(encoded, resolver)
         if available:
             kwargs[name] = value
         elif name in ("custom_field_data", "default"):
             kwargs[name] = value if value is not None else ({} if name == "custom_field_data" else None)
             unresolved_values.append((name, encoded))
         else:
-            return None, [], []
+            return None, [], [], []
     for name, spec in record.get("relations", {}).items():
         field = valid_fields.get(name)
         if not isinstance(field, (models.ForeignKey, models.OneToOneField)):
             continue
-        value, available = _resolve_reference(spec, resolved)
+        value, available = resolver.resolve(spec)
         if available:
+            if value is MISSING_REFERENCE:
+                if not field.null and not field.has_default():
+                    missing_required.append(name)
+            else:
                 kwargs[name] = value
         elif field.null:
-            kwargs[name] = None
             unresolved.append((name, spec))
         else:
-            return None, [], []
+            return None, [], [], []
-    return kwargs, unresolved, unresolved_values
+    return kwargs, unresolved, unresolved_values, missing_required
 
 
-def _set_generic_relations(obj, record, resolved, *, allow_deferred: bool):
+def _set_generic_relations(obj, record, resolver, *, allow_deferred: bool):
     fields = {field.name: field for field in generic_foreign_keys(type(obj))}
     unresolved = []
+    missing_required = []
     for name, spec in record.get("generic_relations", {}).items():
         field = fields.get(name)
         if not field:
             continue
-        value, available = _resolve_reference(spec, resolved)
+        value, available = resolver.resolve(spec)
         if available:
+            if value is MISSING_REFERENCE:
+                ct_field = obj._meta.get_field(field.ct_field)
+                id_field = obj._meta.get_field(field.fk_field)
+                if not ct_field.null or not id_field.null:
+                    missing_required.append(name)
+            else:
                 setattr(obj, name, value)
         elif allow_deferred:
             ct_field = obj._meta.get_field(field.ct_field)
             id_field = obj._meta.get_field(field.fk_field)
             if ct_field.null and id_field.null:
-                setattr(obj, field.ct_field, None)
-                setattr(obj, field.fk_field, None)
                 unresolved.append((name, spec))
             else:
                 return None
         else:
             return None
-    return unresolved
+    return unresolved, missing_required
 
 
 def _set_files(obj, record, assets, saved_files, *, dry_run: bool):
@@ -308,7 +303,7 @@ def _cleanup_files(saved_files):
             logger.warning("Could not remove rolled-back import file %s", name, exc_info=True)
 
 
-def _apply_m2m(obj, record, resolved):
+def _apply_m2m(obj, record, resolver):
     for name, specs in record.get("many_to_many", {}).items():
         try:
             manager = getattr(obj, name)
@@ -316,9 +311,11 @@ def _apply_m2m(obj, record, resolved):
             continue
         values = []
         for spec in specs:
-            value, available = _resolve_reference(spec, resolved)
+            value, available = resolver.resolve(spec)
             if not available:
                 raise ArchiveValidationError(f"M2M-Referenz für {record['id']} konnte nicht aufgelöst werden.")
+            if value is MISSING_REFERENCE:
+                continue
             values.append(value)
         manager.set(values)
 
@@ -347,6 +344,7 @@ def import_archive(parsed: ParsedArchive, *, conflict_strategy: str, dry_run: bo
 
     report = ImportReport(dry_run=dry_run, warnings=list(parsed.warnings))
     resolved = {}
+    resolver = ReferenceResolver(resolved, report.warnings, _model_for)
     deferred_relations = []
     deferred_generic = []
     deferred_values = []
@@ -360,11 +358,13 @@ def import_archive(parsed: ParsedArchive, *, conflict_strategy: str, dry_run: bo
                 progressed = False
                 for record_id, record in list(pending.items()):
                     model = _model_for(record["model"])
-                    kwargs, unresolved, unresolved_value_fields = _field_kwargs(model, record, resolved)
+                    kwargs, unresolved, unresolved_value_fields, missing_required = _field_kwargs(
+                        model, record, resolver
+                    )
                     if kwargs is None:
                         continue
                     try:
-                        existing = _find_existing(source_instance, model, record, resolved)
+                        existing = _find_existing(source_instance, model, record, resolver)
                     except IdentityNotReady:
                         continue
                     if existing is not None and conflict_strategy == "fail":
@@ -377,8 +377,16 @@ def import_archive(parsed: ParsedArchive, *, conflict_strategy: str, dry_run: bo
                         obj = existing or model()
                         for name, value in kwargs.items():
                             setattr(obj, name, value)
-                        generic_unresolved = _set_generic_relations(obj, record, resolved, allow_deferred=True)
+                        generic_result = _set_generic_relations(obj, record, resolver, allow_deferred=True)
-                        if generic_unresolved is None:
+                        if generic_result is None:
+                            continue
+                        generic_unresolved, missing_generic = generic_result
+                        missing_required.extend(missing_generic)
+                        if missing_required and existing is None:
+                            resolver.skip(record_id, record["model"], missing_required)
+                            report.add(record["model"], "skipped")
+                            pending.pop(record_id)
+                            progressed = True
                             continue
                         _set_files(obj, record, parsed.assets, saved_files, dry_run=dry_run)
                         obj.save()
@@ -405,9 +413,11 @@ def import_archive(parsed: ParsedArchive, *, conflict_strategy: str, dry_run: bo
             for record_id, name, spec in deferred_relations:
                 if record_id not in writable:
                     continue
-                value, available = _resolve_reference(spec, resolved)
+                value, available = resolver.resolve(spec)
                 if not available:
                     raise ArchiveValidationError(f"Referenz {name} für {record_id} konnte nicht aufgelöst werden.")
+                if value is MISSING_REFERENCE:
+                    continue
                 obj = resolved[record_id]
                 setattr(obj, name, value)
                 obj.save(update_fields=[name])
@@ -415,9 +425,11 @@ def import_archive(parsed: ParsedArchive, *, conflict_strategy: str, dry_run: bo
             for record_id, name, spec in deferred_generic:
                 if record_id not in writable:
                     continue
-                value, available = _resolve_reference(spec, resolved)
+                value, available = resolver.resolve(spec)
                 if not available:
                     raise ArchiveValidationError(f"Generische Referenz {name} für {record_id} fehlt.")
+                if value is MISSING_REFERENCE:
+                    continue
                 obj = resolved[record_id]
                 setattr(obj, name, value)
                 field = next(field for field in generic_foreign_keys(type(obj)) if field.name == name)
@@ -426,7 +438,7 @@ def import_archive(parsed: ParsedArchive, *, conflict_strategy: str, dry_run: bo
             for record_id, name, encoded in deferred_values:
                 if record_id not in writable:
                     continue
-                value, available = _decode_archived_value(encoded, resolved)
+                value, available = _decode_archived_value(encoded, resolver)
                 if not available:
                     raise ArchiveValidationError(f"Custom-Field-Referenz {name} für {record_id} fehlt.")
                 obj = resolved[record_id]
@@ -435,7 +447,7 @@ def import_archive(parsed: ParsedArchive, *, conflict_strategy: str, dry_run: bo
 
             for record_id, record in records.items():
                 if record_id in writable:
-                    _apply_m2m(resolved[record_id], record, resolved)
+                    _apply_m2m(resolved[record_id], record, resolver)
 
             if dry_run:
                 transaction.set_rollback(True)

netbox_export/services/references.py

@@ -0,0 +1,68 @@
+from __future__ import annotations
+
+from .codec import decode_scalar
+from .exceptions import ArchiveValidationError
+
+MISSING_REFERENCE = object()
+
+
+class ReferenceResolver:
+    def __init__(self, resolved, warnings, model_loader):
+        self.resolved = resolved
+        self.warnings = warnings
+        self.model_loader = model_loader
+        self.skipped = set()
+        self._external_cache = {}
+        self._warning_keys = set()
+
+    def warn(self, key, message):
+        if key not in self._warning_keys:
+            self._warning_keys.add(key)
+            self.warnings.append(message)
+
+    def skip(self, record_id, model_label, field_names):
+        self.skipped.add(record_id)
+        fields = ", ".join(field_names)
+        self.warn(
+            ("skipped", record_id),
+            f"{record_id} ({model_label}) wurde wegen fehlender Pflichtreferenz übersprungen: {fields}.",
+        )
+
+    def _external_object(self, spec):
+        cache_key = repr(spec)
+        if cache_key in self._external_cache:
+            return self._external_cache[cache_key]
+        model = self.model_loader(spec["model"])
+        lookup = {key: decode_scalar(value) for key, value in spec.get("lookup", {}).items()}
+        reason = None
+        try:
+            value = model._default_manager.get(**lookup)
+        except model.DoesNotExist:
+            value = MISSING_REFERENCE
+            reason = "nicht gefunden"
+        except model.MultipleObjectsReturned:
+            value = MISSING_REFERENCE
+            reason = "nicht eindeutig"
+        if value is MISSING_REFERENCE:
+            self.warn(
+                ("external", cache_key),
+                f"Externe Referenz ausgelassen: {spec['model']} mit {lookup} ({reason}).",
+            )
+        self._external_cache[cache_key] = value
+        return value
+
+    def resolve(self, spec):
+        if spec is None:
+            return None, True
+        if "ref" in spec:
+            record_id = spec["ref"]
+            if record_id in self.skipped:
+                self.warn(
+                    ("internal", record_id),
+                    f"Referenzen auf das übersprungene Objekt {record_id} wurden ausgelassen.",
+                )
+                return MISSING_REFERENCE, True
+            return self.resolved.get(record_id), record_id in self.resolved
+        if "external" in spec:
+            return self._external_object(spec["external"]), True
+        raise ArchiveValidationError("Eine Objektreferenz im Archiv ist ungültig.")

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "netbox-export"
-version = "0.3.0"
+version = "0.3.1"
 description = "Portable ZIP export and import for scoped NetBox data"
 readme = "README.md"
 requires-python = ">=3.12"

tests/test_references.py

@@ -0,0 +1,91 @@
+from netbox_export.services.references import MISSING_REFERENCE, ReferenceResolver
+
+
+class DoesNotExist(Exception):
+    pass
+
+
+class MultipleObjectsReturned(Exception):
+    pass
+
+
+class FakeManager:
+    def __init__(self, result):
+        self.result = result
+        self.calls = 0
+
+    def get(self, **lookup):
+        self.calls += 1
+        if isinstance(self.result, Exception):
+            raise self.result
+        return self.result
+
+
+def fake_model(manager):
+    return type(
+        "FakeModel",
+        (),
+        {
+            "DoesNotExist": DoesNotExist,
+            "MultipleObjectsReturned": MultipleObjectsReturned,
+            "_default_manager": manager,
+        },
+    )
+
+
+def test_missing_external_reference_is_omitted_and_warned_once():
+    manager = FakeManager(DoesNotExist())
+    model = fake_model(manager)
+    warnings = []
+    resolver = ReferenceResolver({}, warnings, lambda label: model)
+    spec = {"external": {"model": "users.user", "lookup": {"username": "lke"}}}
+
+    first, first_available = resolver.resolve(spec)
+    second, second_available = resolver.resolve(spec)
+
+    assert first is MISSING_REFERENCE
+    assert second is MISSING_REFERENCE
+    assert first_available is True
+    assert second_available is True
+    assert manager.calls == 1
+    assert warnings == [
+        "Externe Referenz ausgelassen: users.user mit {'username': 'lke'} (nicht gefunden)."
+    ]
+
+
+def test_ambiguous_external_reference_is_omitted():
+    manager = FakeManager(MultipleObjectsReturned())
+    model = fake_model(manager)
+    warnings = []
+    resolver = ReferenceResolver({}, warnings, lambda label: model)
+
+    value, available = resolver.resolve(
+        {"external": {"model": "users.group", "lookup": {"name": "NetBox"}}}
+    )
+
+    assert value is MISSING_REFERENCE
+    assert available is True
+    assert warnings == [
+        "Externe Referenz ausgelassen: users.group mit {'name': 'NetBox'} (nicht eindeutig)."
+    ]
+
+
+def test_reference_to_skipped_record_is_omitted_and_warned_once():
+    warnings = []
+    resolver = ReferenceResolver({}, warnings, lambda label: None)
+    resolver.skip("dcim.rackreservation:17", "dcim.rackreservation", ["user"])
+
+    first, first_available = resolver.resolve({"ref": "dcim.rackreservation:17"})
+    second, second_available = resolver.resolve({"ref": "dcim.rackreservation:17"})
+
+    assert first is MISSING_REFERENCE
+    assert second is MISSING_REFERENCE
+    assert first_available is True
+    assert second_available is True
+    assert warnings == [
+        (
+            "dcim.rackreservation:17 (dcim.rackreservation) wurde wegen fehlender "
+            "Pflichtreferenz übersprungen: user."
+        ),
+        "Referenzen auf das übersprungene Objekt dcim.rackreservation:17 wurden ausgelassen.",
+    ]