Calculate comment depths when building CommentTree

Previously I was just using Jinja's built-in loop.depth0 to output
comment depth in HTML, but actually attaching a depth attribute to the
comments will allow it to be used elsewhere as well. It's possible this
should even be on the Comment model itself, since it never changes and
might be useful in other ways.

tildes/tests/test_comment.py

@@ -189,6 +189,11 @@ def test_comment_tree(db, topic, session_user):
     assert child.replies == []
     assert child2.replies == [subchild, subchild2]
 
+    # check depth values are as expected
+    assert root.depth == 0
+    assert child.depth == 1
+    assert subchild.depth == 2
+
     # delete child2 (which has replies) and ensure it stays in the tree
     child2.is_deleted = True
     db.commit()

tildes/tildes/models/comment/comment_tree.py

@@ -69,6 +69,8 @@ class CommentTree:
         for comment in self.comments:
             if comment.parent_comment_id:
                 parent_comment = self.comments_by_id[comment.parent_comment_id]
+
+                comment.depth = parent_comment.depth + 1
                 parent_comment.replies.append(comment)
 
                 # if this comment isn't deleted, work back up towards the root,
@@ -83,6 +85,7 @@ class CommentTree:
                         next_parent_id = parent_comment.parent_comment_id
                         parent_comment = self.comments_by_id[next_parent_id]
             else:
+                comment.depth = 0
                 self.tree.append(comment)
 
     @staticmethod
@@ -235,6 +238,7 @@ class CommentInTree(ObjectProxy):
         self.replies: List[CommentInTree] = []
         self.has_visible_descendant = False
         self.num_children = 0
+        self.depth: Optional[int] = None
 
     @property
     def has_uncollapsed_descendant(self) -> bool:

tildes/tildes/templates/macros/comments.jinja2

@@ -21,7 +21,7 @@
 
       {# only add depth attr if we're rendering multiple comments at once #}
       {% if not is_individual_comment %}
-        data-comment-depth="{{ loop.depth0 }}"
+        data-comment-depth="{{ comment.depth }}"
       {% endif %}
 
       {% if request.has_permission("label", comment) %}