Make sure collection exists before items are added (#38424)

app/services/activitypub/process_featured_collection_service.rb

@@ -17,20 +17,15 @@ class ActivityPub::ProcessFeaturedCollectionService
       Collection.transaction do
         @collection = @account.collections.find_or_initialize_by(uri: @json['id'])
 
-        @collection.update!(
+        @collection.update!(collection_attributes)
-          local: false,
-          name: (@json['name'] || '')[0, Collection::NAME_LENGTH_HARD_LIMIT],
-          description_html: truncated_summary,
-          language:,
-          sensitive: @json['sensitive'],
-          discoverable: @json['discoverable'],
-          original_number_of_items: @json['totalItems'] || 0,
-          tag_name: @json.dig('topic', 'name')
-        )
 
-        process_items!
+        @items = (@json['orderedItems'] || [])[0, ITEMS_LIMIT]
+        item_uris = @items.filter_map { |i| value_or_id(i) }
+        @collection.collection_items.where.not(uri: item_uris).delete_all
       end
 
+      process_items!
+
       @collection
     end
   end
@@ -46,14 +41,22 @@ class ActivityPub::ProcessFeaturedCollectionService
     @json['summaryMap']&.keys&.first
   end
 
+  def collection_attributes
+    {
+      local: false,
+      name: (@json['name'] || '')[0, Collection::NAME_LENGTH_HARD_LIMIT],
+      description_html: truncated_summary,
+      language:,
+      sensitive: @json['sensitive'],
+      discoverable: @json['discoverable'],
+      original_number_of_items: @json['totalItems'] || 0,
+      tag_name: @json.dig('topic', 'name'),
+    }
+  end
+
   def process_items!
-    uris = []
+    @items.each_with_index do |item_json, index|
-    items = @json['orderedItems'] || []
-    items.take(ITEMS_LIMIT).each_with_index do |item_json, index|
-      uris << value_or_id(item_json)
       ActivityPub::ProcessFeaturedItemWorker.perform_async(@collection.id, item_json, index + 1, @request_id)
     end
-    uris.compact!
-    @collection.collection_items.where.not(uri: uris).delete_all
   end
 end