From d2e2b3d2b1cdddfb71ea6b52335902f33672bffe Mon Sep 17 00:00:00 2001
From: evazion <noizave@gmail.com>
Date: Sat, 14 Apr 2018 10:51:29 -0500
Subject: [PATCH 1/3] pagination: add paginator tests.

---
 test/unit/paginator_test.rb | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 test/unit/paginator_test.rb

diff --git a/test/unit/paginator_test.rb b/test/unit/paginator_test.rb
new file mode 100644
index 000000000..2f1eb9767
--- /dev/null
+++ b/test/unit/paginator_test.rb
@@ -0,0 +1,34 @@
+require 'test_helper'
+
+class PaginatorTest < ActiveSupport::TestCase
+  setup do
+    @posts = FactoryBot.create_list(:post, 5)
+  end
+
+  context "sequential pagination (before)" do
+    should "return the correct set of records" do
+      expected_posts = Post.limit(3).order(id: :desc)
+      posts = Post.paginate("b9999999", limit: 3)
+
+      assert_equal(expected_posts.map(&:id), posts.map(&:id))
+    end
+  end
+
+  context "sequential pagination (after)" do
+    should "return the correct set of records" do
+      expected_posts = Post.limit(3).order(id: :asc).reverse
+      posts = Post.paginate("a0", limit: 3)
+
+      assert_equal(expected_posts.map(&:id), posts.map(&:id))
+    end
+  end
+
+  context "numbered pagination" do
+    should "return the correct set of records" do
+      expected_posts = Post.limit(3).order(id: :desc)
+      posts = Post.order(id: :desc).paginate("1", limit: 3)
+
+      assert_equal(expected_posts.map(&:id), posts.map(&:id))
+    end
+  end
+end

From 074b66bf274e0fdc5ce1e2d9f43693cb03dc0e72 Mon Sep 17 00:00:00 2001
From: evazion <noizave@gmail.com>
Date: Sat, 14 Apr 2018 10:53:23 -0500
Subject: [PATCH 2/3] pagination: prefer `extending` over `extend.

The `extending` method is the preferred way to add methods to an ActiveRecord collection.

* http://api.rubyonrails.org/classes/ActiveRecord/QueryMethods.html#method-i-extending
* https://ruby-doc.org/core-2.5.0/Object.html#method-i-extend
---
 .../paginator/active_record_extension.rb      | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/app/logical/danbooru/paginator/active_record_extension.rb b/app/logical/danbooru/paginator/active_record_extension.rb
index 667c8dc73..1e9488495 100644
--- a/app/logical/danbooru/paginator/active_record_extension.rb
+++ b/app/logical/danbooru/paginator/active_record_extension.rb
@@ -37,17 +37,17 @@ module Danbooru
             c = c.where("#{table_name}.id < ?", before_id.to_i)
           end
 
-          c.reorder("#{table_name}.id desc").tap do |obj|
-            obj.extend(SequentialCollectionExtension)
-            obj.sequential_paginator_mode = :before
-          end
+          c = c.reorder("#{table_name}.id desc")
+          c = c.extending(SequentialCollectionExtension)
+          c.sequential_paginator_mode = :before
+          c
         end
 
         def paginate_sequential_after(after_id)
-          limit(records_per_page + 1).where("#{table_name}.id > ?", after_id.to_i).reorder("#{table_name}.id asc").tap do |obj|
-            obj.extend(SequentialCollectionExtension)
-            obj.sequential_paginator_mode = :after
-          end
+          c = limit(records_per_page + 1).where("#{table_name}.id > ?", after_id.to_i).reorder("#{table_name}.id asc")
+          c = c.extending(SequentialCollectionExtension)
+          c.sequential_paginator_mode = :after
+          c
         end
 
         def paginate_numbered(page)
@@ -57,8 +57,7 @@ module Danbooru
             raise ::Danbooru::Paginator::PaginationError.new("You cannot go beyond page #{Danbooru.config.max_numbered_pages}. Please narrow your search terms.")
           end
 
-          limit(records_per_page).offset((page - 1) * records_per_page).tap do |obj|
-            obj.extend(NumberedCollectionExtension)
+          extending(NumberedCollectionExtension).limit(records_per_page).offset((page - 1) * records_per_page).tap do |obj|
             if records_per_page > 0
               obj.total_pages = (obj.total_count.to_f / records_per_page).ceil
             else

From d42ef7d7dc156c7fb44dd30f12319389612cc2db Mon Sep 17 00:00:00 2001
From: evazion <noizave@gmail.com>
Date: Sat, 14 Apr 2018 10:18:20 -0500
Subject: [PATCH 3/3] Fix #3642: Issues with sequential pagination.

As of Rails 5, overriding `to_a` on an ActiveRecord collection does
nothing. We need to override `records` instead.

ref: https://github.com/rails/rails/commit/cdd45fa09d76f7c16ccbb6682e672a44f82174a0
---
 .../danbooru/paginator/sequential_collection_extension.rb    | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/app/logical/danbooru/paginator/sequential_collection_extension.rb b/app/logical/danbooru/paginator/sequential_collection_extension.rb
index 9cee8fc4a..c78da7846 100644
--- a/app/logical/danbooru/paginator/sequential_collection_extension.rb
+++ b/app/logical/danbooru/paginator/sequential_collection_extension.rb
@@ -19,7 +19,10 @@ module Danbooru
         end
       end
 
-      def to_a
+      # XXX Hack: in sequential pagination we fetch one more record than we need
+      # so that we can tell when we're on the first or last page. Here we override
+      # a rails internal method to discard that extra record. See #2044, #3642.
+      def records
         if sequential_paginator_mode == :before
           super.first(records_per_page)
         else