Replace awesome_nested_set with a plain parent_id-based NestedTree concern

Root-caused this session: appending a child to any node never widened
that parent's own rgt boundary, on the pinned revision (Gemfile tracked
main directly, chasing a too-conservative gemspec constraint - not, as
first assumed, a deliberate pin to avoid a known bug). Reproduced
cleanly on a single ordinary create with no concurrency and no bulk
operation involved, confirmed via the gem's own SetValidator, then
confirmed as the root cause of nodes_controller_test.rb's 3 long-standing
"pre-existing" failures - not three separate mysteries, one bug.

admin_controller's sitemap needed its own real conversion, not just a
drop-in: awesome_nested_set's lft column implicitly provided correct
depth-first tree order for free, which the old code combined with a
separate class-level each_with_level iterator. Both replaced by one
method, self_and_descendants_ordered_with_level, computing an ordered
[node, level] list in a single query-then-walk pass - checked against
the actual view template first (admin/index.html.erb) rather than
assumed, since it relies on list order alone to render correct visual
nesting.

lft/rgt/depth columns intentionally left in schema, unused - dropping
them is a separate, deliberately deferred migration once this is proven
running for a while, not bundled with the behavior change.

1 files changed, 6 insertions, 19 deletions

diff --git a/app/models/node.rb b/app/models/node.rb
index 2177f15..fc23dc1 100644
--- a/app/models/node.rb
+++ b/app/models/node.rb
@@ -1,6 +1,6 @@
 class Node < ApplicationRecord
   # Mixins and Plugins
-  acts_as_nested_set
+  include NestedTree
 
   # Associations
   has_many    :pages, -> { order("revision ASC") }, :dependent => :destroy
@@ -21,16 +21,6 @@ class Node < ApplicationRecord
   validates_uniqueness_of :slug, :scope => :parent_id, :unless => -> { parent_id.nil? }
   validates_presence_of   :parent_id,                  :unless => -> { Node.root.nil? }
 
-  validate :borders       # This should never ever happen.
-
-  # Index for Fulltext Search
-  # define_index do
-  #   indexes head.translations.title
-  #   indexes slug
-  #   indexes unique_name
-  #   indexes head.translations.body
-  # end
-
   # Class methods
 
   # Returns a page for a given node. If no revision is supplied, it returns
@@ -254,10 +244,13 @@ class Node < ApplicationRecord
     # Watch out recursion ahead! update_unique_name itself triggers this
     # after_save callback which invokes update_unique_name on its children.
     # Hopefully until no childrens occur
+    #
+    # Queries parent_id directly rather than the NestedTree#children
+    # association out of habit from the old awesome_nested_set-avoidance
+    # workaround - no longer strictly necessary now that children is
+    # equally safe, but left as-is since it already works correctly.
     def update_unique_names_of_children
       unless root?
-        # Use parent_id-based traversal instead of lft/rgt descendants
-        # due to awesome_nested_set not refreshing parent lft/rgt in memory
         Node.where(:parent_id => self.id).each do |child|
           child.reload
           child.update_unique_name
@@ -265,10 +258,4 @@ class Node < ApplicationRecord
         end
       end
     end
-
-    def borders
-      if lft && rgt && (lft > rgt)
-        errors.add("Fuck!. lft should never be smaller than rgt")
-      end
-    end
 end