Automatically prune removed options from existing instances

src/documents/signals/handlers.py

@@ -367,21 +367,6 @@ class CannotMoveFilesException(Exception):
     pass
 
 
-# should be disabled in /src/documents/management/commands/document_importer.py handle
-@receiver(models.signals.post_save, sender=CustomField)
-def update_cf_instance_documents(sender, instance: CustomField, **kwargs):
-    """
-    'Select' custom field instances get their end-user value (e.g. in file names) from the select_options in extra_data,
-    which is contained in the custom field itself. So when the field is changed, we (may) need to update the file names
-    of all documents that have this custom field.
-    """
-    if (
-        instance.data_type == CustomField.FieldDataType.SELECT
-    ):  # Only select fields, for now
-        for cf_instance in instance.fields.all():
-            update_filename_and_move_files(sender, cf_instance)
-
-
 # should be disabled in /src/documents/management/commands/document_importer.py handle
 @receiver(models.signals.post_save, sender=CustomFieldInstance)
 @receiver(models.signals.m2m_changed, sender=Document.tags.through)
@@ -520,6 +505,34 @@ def update_filename_and_move_files(
             )
 
 
+# should be disabled in /src/documents/management/commands/document_importer.py handle
+@receiver(models.signals.post_save, sender=CustomField)
+def check_paths_and_prune_custom_fields(sender, instance: CustomField, **kwargs):
+    """
+    When a custom field is updated:
+    1. 'Select' custom field instances get their end-user value (e.g. in file names) from the select_options in extra_data,
+    which is contained in the custom field itself. So when the field is changed, we (may) need to update the file names
+    of all documents that have this custom field.
+    2. If a 'Select' field option was removed, we need to nullify the custom field instances that have the option.
+    """
+    if (
+        instance.data_type == CustomField.FieldDataType.SELECT
+    ):  # Only select fields, for now
+        for cf_instance in instance.fields.all():
+            options = instance.extra_data.get("select_options", [])
+            try:
+                next(
+                    option["label"]
+                    for option in options
+                    if option["id"] == cf_instance.value
+                )
+            except StopIteration:
+                # The value of this custom field instance is not in the select options anymore
+                cf_instance.value_select = None
+                cf_instance.save()
+            update_filename_and_move_files(sender, cf_instance)
+
+
 def set_log_entry(sender, document: Document, logging_group=None, **kwargs):
     ct = ContentType.objects.get(model="document")
     user = User.objects.get(username="consumer")