support copying of fields in ParentalManyToManyField

wagtail_localize/fields.py

@@ -1,5 +1,5 @@
 from django.db import models
-from modelcluster.fields import ParentalKey
+from modelcluster.fields import ParentalKey, ParentalManyToManyField
 from modelcluster.models import ClusterableModel, get_all_child_relations
 from treebeard.mp_tree import MP_Node
 from wagtail.fields import RichTextField, StreamField
@@ -285,6 +285,13 @@ def copy_synchronised_fields(source, target):
                 else:
                     source.copy_child_relation(field.name, target)
 
+            elif isinstance(field, ParentalManyToManyField):
+                parental_field = getattr(source, field.name)
+                if hasattr(parental_field, "all"):
+                    values = parental_field.all()
+                    if values:
+                        setattr(target, field.attname, values)
+
             else:
                 # For all other fields, just set the attribute
                 setattr(target, field.attname, getattr(source, field.attname))

wagtail_localize/test/models.py

@@ -78,7 +78,7 @@ class TestUUIDSnippet(TranslatableMixin, models.Model):
 
 
 @register_snippet
-class TestParentalSnippet(TranslatableMixin, models.Model):
+class TestParentalSnippet(TranslatableMixin, ClusterableModel):
     field = ParentalManyToManyField(
         TestUUIDModel,
         blank=True,

wagtail_localize/tests/test_translation_model.py

@@ -726,13 +726,10 @@ def test_parental_many_to_many(self):
             target_locale=self.fr_locale,
         )
 
-        # field_context = TranslationContext.objects.get(path="field")
-        # self.assertIsNotNone(field_context)
-
         translation.save_target()
 
         translated_snippet = snippet.get_translation(self.fr_locale)
-        self.assertEqual(translated_snippet.field.charfield, "Some Test")
+        self.assertEqual(list(translated_snippet.field.all()), [foreign_key_target])
 
 
 @override_settings(WAGTAILLOCALIZE_DISABLE_ON_DELETE=True)