OpenGraph: fall back on book cover when preview images are disabled

bookwyrm/models/status.py

@@ -195,7 +195,7 @@ class Status(OrderedCollectionPageMixin, BookWyrmModel):
         """image to use as preview in meta tags when only this status is shown"""
         if self.mention_books.exists():
             book = self.mention_books.first()
-            return book.preview_image
+            return book.preview_image or book.cover
         else:
             return self.user.preview_image
 
@@ -324,7 +324,7 @@ class BookStatus(Status):
 
     @property
     def page_image(self):
-        return self.book.preview_image or super().page_image
+        return self.book.preview_image or self.book.cover or super().page_image
 
 
 class Comment(BookStatus):

bookwyrm/templates/book/book.html

@@ -9,7 +9,8 @@
 {% block title %}{{ book|book_title }}{% endblock %}
 
 {% block opengraph %}
-    {% include 'snippets/opengraph.html' with title=book.title description=book|book_description image=book.preview_image %}
+    {% firstof book.preview_image book.cover as book_image %}
+    {% include 'snippets/opengraph.html' with title=book.title description=book|book_description image=book_image %}
 {% endblock %}
 
 {% block content %}