fix: resolve constrained relations before insert

tests/test_importer_plugin_compat.py

@@ -1,3 +1,5 @@
+from typing import ClassVar
+
 from django.db import models
 
 from netbox_export.services.importer import _field_kwargs
@@ -16,6 +18,24 @@ class TenantManagedObject(models.Model):
         app_label = "compat_tests"
 
 
+class Platform(models.Model):
+    class Meta:
+        app_label = "compat_tests"
+
+
+class ConstrainedInstallation(models.Model):
+    platform = models.ForeignKey(Platform, on_delete=models.PROTECT, null=True)
+
+    class Meta:
+        app_label = "compat_tests"
+        constraints: ClassVar[list] = [
+            models.CheckConstraint(
+                condition=models.Q(platform__isnull=False),
+                name="compat_tests_installation_platform",
+            )
+        ]
+
+
 def tenant_record():
     return {
         "fields": {},
@@ -53,3 +73,23 @@ def test_unresolved_tenant_also_blocks_when_policy_detection_is_unavailable():
     assert unresolved == []
     assert unresolved_values == []
     assert missing_required == []
+
+
+def test_unresolved_relation_in_check_constraint_blocks_initial_save():
+    resolver = ReferenceResolver({}, [], lambda label: None)
+    record = {
+        "fields": {},
+        "relations": {"platform": {"ref": "compat_tests.platform:5"}},
+    }
+
+    kwargs, unresolved, unresolved_values, missing_required = _field_kwargs(
+        ConstrainedInstallation,
+        record,
+        resolver,
+        tenant_required=False,
+    )
+
+    assert kwargs is None
+    assert unresolved == []
+    assert unresolved_values == []
+    assert missing_required == []

tests/test_plugin_compat.py

@@ -1,11 +1,14 @@
 from types import SimpleNamespace
 
 from django.core.exceptions import FieldDoesNotExist, ValidationError
+from django.db import models
 
 from netbox_export.services.plugin_compat import (
     MISSING_TENANT_MESSAGE,
     PluginCompatibility,
+    check_constraint_field_names,
     is_tenant_relation,
+    relation_required_before_save,
 )
 
 
@@ -82,6 +85,22 @@ def test_identifies_tenant_relation():
     assert is_tenant_relation(relation_field("site", "dcim.site")) is False
 
 
+def test_identifies_relations_used_by_check_constraint():
+    constraint = models.CheckConstraint(
+        condition=(
+            models.Q(device__isnull=False, virtualmachine__isnull=True)
+            | models.Q(device__isnull=True, virtualmachine__isnull=False)
+        ),
+        name="platform",
+    )
+    model = type("ConstrainedModel", (), {"_meta": SimpleNamespace(constraints=[constraint])})
+    field = relation_field("device", "dcim.device")
+    field.model = model
+
+    assert check_constraint_field_names(model) == frozenset({"device", "virtualmachine"})
+    assert relation_required_before_save(field) is True
+
+
 def test_creates_and_assigns_auto_import_tenant_when_policy_is_active():
     manager = FakeTenantManager()
     tenant_model = type("TenantModel", (), {"_default_manager": manager})