Fix not_in search with deep nesting

lib/ransack/nodes/condition.rb

@@ -286,7 +286,13 @@ def negative?
       def arel_predicate
         predicate = attributes.map { |attribute|
           association = attribute.parent
-          if negative? && attribute.associated_collection?
+          parent_table = association.table
+
+          if parent_table.class == Arel::Nodes::TableAlias && association.reflection.class == ActiveRecord::Reflection::ThroughReflection
+            parent_table.right = parent_table.left.name
+          end
+
+          if negative? && attribute.associated_collection? && not_nested_condition(attribute, parent_table)
             query = context.build_correlated_subquery(association)
             context.remove_association(association)
             if self.predicate_name == 'not_null' && self.value
@@ -313,6 +319,10 @@ def arel_predicate
         predicate
       end
 
+      def not_nested_condition(attribute, parent_table)
+        parent_table.class != Arel::Nodes::TableAlias && attribute.name.starts_with?(parent_table.name)
+      end
+
       private
 
       def combinator_method

spec/ransack/adapters/active_record/base_spec.rb

@@ -191,6 +191,41 @@ module ActiveRecord
           end
         end
 
+        context 'negative conditions on related object with HABTM associations' do
+          let(:medieval) { Tag.create!(name: 'Medieval') }
+          let(:fantasy)  { Tag.create!(name: 'Fantasy') }
+          let(:arthur)   { Article.create!(title: 'King Arthur') }
+          let(:marco)    { Article.create!(title: 'Marco Polo') }
+          let(:comment_arthur)  { marco.comments.create!(body: 'King Arthur comment') }
+          let(:comment_marco)   { arthur.comments.create!(body: 'Marco Polo comment') }
+
+          before do
+            comment_arthur.tags << medieval
+            comment_marco.tags << fantasy
+          end
+
+          it 'removes redundant joins from top query' do
+            s = Article.ransack(comments_tags_name_not_eq: "Fantasy")
+            sql = s.result.to_sql
+            expect(sql).to include('LEFT OUTER JOIN')
+          end
+
+          it 'handles != for single values' do
+            s = Article.ransack(comments_tags_name_not_eq: "Fantasy")
+            articles = s.result.to_a
+            expect(articles).to include marco
+            expect(articles).to_not include arthur
+          end
+
+          it 'handles NOT IN for multiple attributes' do
+            s = Article.ransack(comments_tags_name_not_in: ["Fantasy", "Scifi"])
+            articles = s.result.to_a
+
+            expect(articles).to include marco
+            expect(articles).to_not include arthur
+          end
+        end
+
         context 'negative conditions on self-referenced associations' do
           let(:pop) { Person.create!(name: 'Grandpa') }
           let(:dad) { Person.create!(name: 'Father') }

spec/ransack/search_spec.rb

@@ -178,7 +178,7 @@ module Ransack
         #     AND "articles"."title" = 'Test' AND "articles"."published" = 't' AND ('default_scope' = 'default_scope')
         # ) ORDER BY "people"."id" DESC
 
-        pending("spec should pass, but I do not know how/where to fix lib code")
+        #pending("spec should pass, but I do not know how/where to fix lib code")
         s = Search.new(Person, published_articles_title_not_eq: 'Test')
         expect(s.result.to_sql).to include 'default_scope'
         expect(s.result.to_sql).to include 'published'

spec/support/schema.rb

@@ -220,12 +220,14 @@ class Article < ::Article
 class Comment < ApplicationRecord
   belongs_to :article
   belongs_to :person
+  has_and_belongs_to_many :tags
 
   default_scope { where(disabled: false) }
 end
 
 class Tag < ApplicationRecord
   has_and_belongs_to_many :articles
+  has_and_belongs_to_many :comments
 end
 
 class Note < ApplicationRecord
@@ -298,6 +300,11 @@ def self.create
         t.integer  :tag_id
       end
 
+      create_table :comments_tags, force: true, id: false do |t|
+        t.integer  :comment_id
+        t.integer  :tag_id
+      end
+
       create_table :notes, force: true do |t|
         t.integer  :notable_id
         t.string   :notable_type