Fix SynchronizedField translation for ParentalManyToManyField (#564)

Fixes #563

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/migrations/0004_testparentalsnippet.py

@@ -0,0 +1,53 @@
+# Generated by Django 3.2.5 on 2022-05-06 18:53
+
+from django.db import migrations, models
+import django.db.models.deletion
+import modelcluster.fields
+import uuid
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("wagtail_localize_test", "0003_wagtail_3_use_json_field"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="TestParentalSnippet",
+            fields=[
+                (
+                    "id",
+                    models.AutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                (
+                    "translation_key",
+                    models.UUIDField(default=uuid.uuid4, editable=False),
+                ),
+                (
+                    "field",
+                    modelcluster.fields.ParentalManyToManyField(
+                        blank=True, to="wagtail_localize_test.TestUUIDModel"
+                    ),
+                ),
+                (
+                    "locale",
+                    models.ForeignKey(
+                        editable=False,
+                        on_delete=django.db.models.deletion.PROTECT,
+                        related_name="+",
+                        to="wagtailcore.locale",
+                    ),
+                ),
+            ],
+            options={
+                "abstract": False,
+                "unique_together": {("translation_key", "locale")},
+            },
+        ),
+    ]

wagtail_localize/test/models.py

@@ -2,7 +2,7 @@
 
 from django.db import models
 from django.utils.translation import gettext_lazy
-from modelcluster.fields import ParentalKey
+from modelcluster.fields import ParentalKey, ParentalManyToManyField
 from modelcluster.models import ClusterableModel
 from wagtail import blocks, telepath
 from wagtail.admin.panels import (
@@ -77,6 +77,16 @@ class TestUUIDSnippet(TranslatableMixin, models.Model):
     translatable_fields = [SynchronizedField("field")]
 
 
+@register_snippet
+class TestParentalSnippet(TranslatableMixin, ClusterableModel):
+    field = ParentalManyToManyField(
+        TestUUIDModel,
+        blank=True,
+    )
+
+    translatable_fields = [SynchronizedField("field")]
+
+
 @register_snippet
 class NonTranslatableSnippet(models.Model):
     field = models.TextField()

wagtail_localize/tests/test_translation_model.py

@@ -32,6 +32,7 @@
 from wagtail_localize.strings import StringValue
 from wagtail_localize.test.models import (
     TestPage,
+    TestParentalSnippet,
     TestSnippet,
     TestUUIDModel,
     TestUUIDSnippet,
@@ -714,6 +715,22 @@ def test_uuid_snippet_save_target(self):
         translated_snippet = snippet.get_translation(self.fr_locale)
         self.assertEqual(translated_snippet.field.charfield, "Some Test")
 
+    def test_parental_many_to_many(self):
+        foreign_key_target = TestUUIDModel.objects.create(charfield="Some Test")
+        snippet = TestParentalSnippet.objects.create()
+        snippet.field = [foreign_key_target]
+
+        source, created = TranslationSource.get_or_create_from_instance(snippet)
+        translation = Translation.objects.create(
+            source=source,
+            target_locale=self.fr_locale,
+        )
+
+        translation.save_target()
+
+        translated_snippet = snippet.get_translation(self.fr_locale)
+        self.assertEqual(list(translated_snippet.field.all()), [foreign_key_target])
+
 
 @override_settings(WAGTAILLOCALIZE_DISABLE_ON_DELETE=True)
 class TestDeleteSourceDisablesTranslation(TestCase):