Fixes #16782: Add object filtering for custom fields

docs/customization/custom-fields.md

@@ -74,6 +74,8 @@ If a default value is specified for a selection field, it must exactly match one
 
 An object or multi-object custom field can be used to refer to a particular NetBox object or objects as the "value" for a custom field. These custom fields must define an `object_type`, which determines the type of object to which custom field instances point.
 
+By default, an object choice field will make all objects of that type available for selection in the drop-down. The list choices can be filtered to show only objects with certain values by providing a `query_params` dict in the Related Object Filter field, as a JSON value. More information about `query_params` can be found [here](./custom-scripts.md#objectvar).
+
 ## Custom Fields in Templates
 
 Several features within NetBox, such as export templates and webhooks, utilize Jinja2 templating. For convenience, objects which support custom field assignment expose custom field data through the `cf` property. This is a bit cleaner than accessing custom field data through the actual field (`custom_field_data`).

docs/models/extras/customfield.md

@@ -42,6 +42,13 @@ The type of data this field holds. This must be one of the following:
 
 For object and multiple-object fields only. Designates the type of NetBox object being referenced.
 
+### Related Object Filter
+
+For object and multi-object custom fields, a filter may be defined to limit the available objects when populating a field value. This filter maps object attributes to values. For example, `{"status": "active"}` will include only objects with a status of "active."
+
+!!! warning
+    This setting is employed for convenience only, and should not be relied upon to enforce data integrity.
+
 ### Weight
 
 A numeric weight used to override alphabetic ordering of fields by name. Custom fields with a lower weight will be listed before those with a higher weight. (Note that weight applies within the context of a custom field group, if defined.)

netbox/extras/api/serializers_/customfields.py

@@ -62,7 +62,7 @@ class Meta:
         fields = [
             'id', 'url', 'display_url', 'display', 'object_types', 'type', 'related_object_type', 'data_type',
             'name', 'label', 'group_name', 'description', 'required', 'search_weight', 'filter_logic', 'ui_visible',
-            'ui_editable', 'is_cloneable', 'default', 'weight', 'validation_minimum', 'validation_maximum',
+            'ui_editable', 'is_cloneable', 'default', 'related_object_filter', 'weight', 'validation_minimum', 'validation_maximum',
             'validation_regex', 'validation_unique', 'choice_set', 'comments', 'created', 'last_updated',
         ]
         brief_fields = ('id', 'url', 'display', 'name', 'description')

netbox/extras/forms/model_forms.py

@@ -67,7 +67,7 @@ class CustomFieldForm(forms.ModelForm):
         FieldSet(
             'search_weight', 'filter_logic', 'ui_visible', 'ui_editable', 'weight', 'is_cloneable', name=_('Behavior')
         ),
-        FieldSet('default', 'choice_set', name=_('Values')),
+        FieldSet('default', 'choice_set', 'related_object_filter', name=_('Values')),
         FieldSet(
             'validation_minimum', 'validation_maximum', 'validation_regex', 'validation_unique', name=_('Validation')
         ),

netbox/extras/migrations/0120_customfield_related_object_filter.py

@@ -0,0 +1,18 @@
+# Generated by Django 5.0.7 on 2024-07-26 01:49
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('extras', '0119_eventrule_event_types'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='customfield',
+            name='related_object_filter',
+            field=models.JSONField(blank=True, null=True),
+        ),
+    ]

netbox/extras/models/customfields.py

@@ -154,6 +154,14 @@ class CustomField(CloningMixin, ExportTemplatesMixin, ChangeLoggedModel):
             'Default value for the field (must be a JSON value). Encapsulate strings with double quotes (e.g. "Foo").'
         )
     )
+    related_object_filter = models.JSONField(
+        blank=True,
+        null=True,
+        help_text=_(
+            'Filter the object selection choices using a query_params dict (must be a JSON value).'
+            'Encapsulate strings with double quotes (e.g. "Foo").'
+        )
+    )
     weight = models.PositiveSmallIntegerField(
         default=100,
         verbose_name=_('display weight'),
@@ -373,6 +381,17 @@ def clean(self):
                 .format(type=self.get_type_display())
             })
 
+        # Related object filter can be set only for object-type fields, and must contain a dictionary mapping (if set)
+        if self.related_object_filter is not None:
+            if self.type not in (CustomFieldTypeChoices.TYPE_OBJECT, CustomFieldTypeChoices.TYPE_MULTIOBJECT):
+                raise ValidationError({
+                    'related_object_filter': _("A related object filter can be defined only for object fields.")
+                })
+            if type(self.related_object_filter) is not dict:
+                raise ValidationError({
+                    'related_object_filter': _("Filter must be defined as a dictionary mapping attributes to values.")
+                })
+
     def serialize(self, value):
         """
         Prepare a value for storage as JSON data.
@@ -511,7 +530,8 @@ def to_form_field(self, set_initial=True, enforce_required=True, enforce_visibil
             field = field_class(
                 queryset=model.objects.all(),
                 required=required,
-                initial=initial
+                initial=initial,
+                query_params=self.related_object_filter
             )
 
         # Multiple objects
@@ -522,6 +542,7 @@ def to_form_field(self, set_initial=True, enforce_required=True, enforce_visibil
                 queryset=model.objects.all(),
                 required=required,
                 initial=initial,
+                query_params=self.related_object_filter
             )
 
         # Text

netbox/extras/tests/test_filtersets.py

@@ -23,7 +23,7 @@
 class CustomFieldTestCase(TestCase, ChangeLoggedFilterSetTests):
     queryset = CustomField.objects.all()
     filterset = CustomFieldFilterSet
-    ignore_fields = ('default',)
+    ignore_fields = ('default', 'related_object_filter')
 
     @classmethod
     def setUpTestData(cls):

netbox/templates/extras/customfield.html

@@ -52,6 +52,14 @@ <h5 class="card-header">{% trans "Custom Field" %}</h5>
           <th scope="row">{% trans "Default Value" %}</th>
           <td>{{ object.default }}</td>
         </tr>
+        <tr>
+          <th scope="row">{% trans "Related object filter" %}</th>
+          {% if object.related_object_filter %}
+            <td><pre>{{ object.related_object_filter|json }}</pre></td>
+          {% else %}
+            <td>{{ ''|placeholder }}</td>
+          {% endif %}
+        </tr>
       </table>
     </div>
     <div class="card">