Make wagtailcore 0002 reversible

wagtail/wagtailcore/migrations/0001_squashed_0016_change_page_url_path_to_text_field.py

@@ -45,15 +45,15 @@ def initial_data(apps, schema_editor):
     )
 
     # Create default site
-    Site.objects.create(
+    Site.objects.get_or_create(
         hostname='localhost',
         root_page_id=homepage.id,
         is_default_site=True
     )
 
     # Create auth groups
-    moderators_group = Group.objects.create(name='Moderators')
-    editors_group = Group.objects.create(name='Editors')
+    moderators_group, created = Group.objects.get_or_create(name='Moderators')
+    editors_group, created = Group.objects.get_or_create(name='Editors')
 
     # Create group permissions
     GroupPagePermission.objects.create(
@@ -91,6 +91,31 @@ def initial_data(apps, schema_editor):
     )
 
 
+def remove_initial_data(apps, schema_editor):
+    """This function does nothing. The below code is commented out together
+    with an explanation of why we don't need to bother reversing any of the
+    initial data"""
+    pass
+    # This does not need to be deleted, Django takes care of it.
+    # page_content_type = ContentType.objects.get(
+    #     model='page',
+    #     app_label='wagtailcore',
+    # )
+
+    # Page objects: Do nothing, the table will be deleted when reversing 0001
+    
+    # Do not reverse Site creation since other models might depend on it
+
+    # Remove auth groups -- is this safe? External objects might depend
+    # on these groups... seems unsafe.
+    # Group.objects.filter(
+    #     name__in=('Moderators', 'Editors')
+    # ).delete()
+    #
+    # Likewise, we're leaving all GroupPagePermission unchanged as users may
+    # have been assigned such permissions and its harmless to leave them.
+
+
 class Migration(migrations.Migration):
 
     replaces = [
@@ -306,6 +331,6 @@ class Migration(migrations.Migration):
             options={'verbose_name': 'Site'},
         ),
         migrations.RunPython(
-            initial_data,
+            initial_data, remove_initial_data
         ),
     ]

wagtail/wagtailcore/migrations/0002_initial_data.py

@@ -81,6 +81,31 @@ def initial_data(apps, schema_editor):
     )
 
 
+def remove_initial_data(apps, schema_editor):
+    """This function does nothing. The below code is commented out together
+    with an explanation of why we don't need to bother reversing any of the
+    initial data"""
+    pass
+    # This does not need to be deleted, Django takes care of it.
+    # page_content_type = ContentType.objects.get(
+    #     model='page',
+    #     app_label='wagtailcore',
+    # )
+
+    # Page objects: Do nothing, the table will be deleted when reversing 0001
+    
+    # Do not reverse Site creation since other models might depend on it
+
+    # Remove auth groups -- is this safe? External objects might depend
+    # on these groups... seems unsafe.
+    # Group.objects.filter(
+    #     name__in=('Moderators', 'Editors')
+    # ).delete()
+    #
+    # Likewise, we're leaving all GroupPagePermission unchanged as users may
+    # have been assigned such permissions and its harmless to leave them.
+
+
 class Migration(migrations.Migration):
 
     dependencies = [
@@ -88,5 +113,5 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
-        migrations.RunPython(initial_data),
+        migrations.RunPython(initial_data, remove_initial_data),
     ]