Fixes serializer handling default dataclass fields

bookwyrm/activitypub/base_activity.py

@@ -74,7 +74,8 @@ class ActivityObject:
             try:
                 value = kwargs[field.name]
             except KeyError:
-                if field.default == MISSING:
+                if field.default == MISSING and \
+                        field.default_factory == MISSING:
                     raise ActivitySerializerError(\
                             'Missing required field: %s' % field.name)
                 value = field.default
@@ -143,6 +144,8 @@ class ActivityObject:
 
         # add images
         for (model_key, value) in image_fields.items():
+            if not value:
+                continue
             getattr(instance, model_key).save(*value, save=True)
 
         # add one to many fields
@@ -188,6 +191,8 @@ def resolve_foreign_key(model, remote_id):
 
 def tag_formatter(tags, tag_type):
     ''' helper function to extract foreign keys from tag activity json '''
+    if not isinstance(tags, list):
+        return []
     items = []
     types = {
         'Book': models.Book,
@@ -207,9 +212,9 @@ def tag_formatter(tags, tag_type):
 
 def image_formatter(image_json):
     ''' helper function to load images and format them for a model '''
-    url = image_json.get('url')
-    if not url:
+    if not image_json or not hasattr(image_json, 'url'):
         return None
+    url = image_json.get('url')
 
     try:
         response = requests.get(url)