Revert "A safe way to create class variables in a multisite environment."

The approach taken by this interface was flawed. We need a better
solution.

app/helpers/application_helper.rb

@@ -8,7 +8,6 @@ require_dependency 'mobile_detection'
 require_dependency 'category_badge'
 require_dependency 'global_path'
 require_dependency 'emoji'
-require_dependency 'multisite_class_var'
 
 module ApplicationHelper
   include CurrentUser
@@ -17,7 +16,9 @@ module ApplicationHelper
   include GlobalPath
   include MultisiteClassVar
 
-  multisite_class_var(:extra_body_classes) { Set.new }
+  def self.extra_body_classes
+    @extra_body_classes ||= Set.new
+  end
 
   def google_universal_analytics_json(ua_domain_name = nil)
     result = {}

app/models/group.rb

@@ -1,14 +1,13 @@
 # frozen_string_literal: true
 
 require_dependency 'enum'
-require_dependency 'multisite_class_var'
 
 class Group < ActiveRecord::Base
   include HasCustomFields
   include AnonCacheInvalidator
-  include MultisiteClassVar
 
-  multisite_class_var(:preloaded_custom_field_names) { Set.new }
+  cattr_accessor :preloaded_custom_field_names
+  self.preloaded_custom_field_names = Set.new
 
   has_many :category_groups, dependent: :destroy
   has_many :group_users, dependent: :destroy

app/models/post.rb

@@ -6,7 +6,6 @@ require_dependency 'post_analyzer'
 require_dependency 'validators/post_validator'
 require_dependency 'plugin/filter'
 require_dependency 'email_cook'
-require_dependency 'multisite_class_var'
 
 require 'archetype'
 require 'digest/sha1'
@@ -17,9 +16,9 @@ class Post < ActiveRecord::Base
   include Searchable
   include HasCustomFields
   include LimitedEdit
-  include MultisiteClassVar
 
-  multisite_class_var(:permitted_create_params) { Set.new }
+  cattr_accessor :permitted_create_params
+  self.permitted_create_params = Set.new
 
   # increase this number to force a system wide post rebake
   BAKED_VERSION = 1

app/models/topic_list.rb

@@ -1,24 +1,29 @@
 require_dependency 'avatar_lookup'
 require_dependency 'primary_group_lookup'
-require_dependency 'multisite_class_var'
 
 class TopicList
   include ActiveModel::Serialization
-  include MultisiteClassVar
 
-  multisite_class_var(:preloaded_custom_fields) { Set.new }
-  multisite_class_var(:preload_callbacks) { Set.new }
+  cattr_accessor :preloaded_custom_fields
+  self.preloaded_custom_fields = Set.new
 
   def self.on_preload(&blk)
-    preload_callbacks << blk
+    (@preload ||= Set.new) << blk
   end
 
   def self.cancel_preload(&blk)
-    preload_callbacks.delete(blk)
+    if @preload
+      @preload.delete blk
+      if @preload.length == 0
+        @preload = nil
+      end
+    end
   end
 
   def self.preload(topics, object)
-    preload_callbacks.each { |p| p.call(topics, object) }
+    if @preload
+      @preload.each { |preload| preload.call(topics, object) }
+    end
   end
 
   attr_accessor :more_topics_url,
@@ -112,8 +117,8 @@ class TopicList
       ft.topic_list = self
     end
 
-    if self.class.preloaded_custom_fields.present?
-      Topic.preload_custom_fields(@topics, self.class.preloaded_custom_fields)
+    if preloaded_custom_fields.present?
+      Topic.preload_custom_fields(@topics, preloaded_custom_fields)
     end
 
     TopicList.preload(@topics, self)

lib/multisite_class_var.rb

@@ -1,20 +0,0 @@
-# Support for a class variable that is multisite aware.
-
-module MultisiteClassVar
-
-  def self.included(base)
-    base.extend ClassMethods
-  end
-
-  module ClassMethods
-    def multisite_class_var(name, &default)
-      @multisite_class_vars ||= {}
-      @multisite_class_vars[name] = {}
-
-      define_singleton_method(name) do
-        @multisite_class_vars[name][RailsMultisite::ConnectionManagement.current_db] ||= default.call
-      end
-    end
-  end
-
-end

lib/topic_view.rb

@@ -2,10 +2,8 @@ require_dependency 'guardian'
 require_dependency 'topic_query'
 require_dependency 'filter_best_posts'
 require_dependency 'gaps'
-require_dependency 'multisite_class_var'
 
 class TopicView
-  include MultisiteClassVar
 
   attr_reader :topic, :posts, :guardian, :filtered_posts, :chunk_size, :print, :message_bus_last_id
   attr_accessor :draft, :draft_key, :draft_sequence, :user_custom_fields, :post_custom_fields
@@ -26,7 +24,9 @@ class TopicView
     @default_post_custom_fields ||= ["action_code_who"]
   end
 
-  multisite_class_var(:post_custom_fields_whitelisters) { Set.new }
+  def self.post_custom_fields_whitelisters
+    @post_custom_fields_whitelisters ||= Set.new
+  end
 
   def self.add_post_custom_fields_whitelister(&block)
     post_custom_fields_whitelisters << block

spec/multisite/multisite_class_var_spec.rb

@@ -1,67 +0,0 @@
-require 'rails_helper'
-require 'multisite_class_var'
-
-RSpec.describe MultisiteClassVar do
-
-  it "will add the class variables" do
-    class_with_set = Class.new do
-      include MultisiteClassVar
-      multisite_class_var(:class_set) { Set.new }
-      multisite_class_var(:class_array) { Array.new }
-    end
-
-    class_with_set.class_set << 'a'
-    class_with_set.class_array << 'c'
-
-    expect(class_with_set.class_set).to contain_exactly('a')
-    expect(class_with_set.class_array).to contain_exactly('c')
-  end
-
-  context "multisite environment" do
-    let(:conn) { RailsMultisite::ConnectionManagement }
-
-    before do
-      @original_provider = SiteSetting.provider
-      SiteSetting.provider = SiteSettings::DbProvider.new(SiteSetting)
-      conn.config_filename = "spec/fixtures/multisite/two_dbs.yml"
-      conn.load_settings!
-      conn.remove_class_variable(:@@current_db)
-    end
-
-    after do
-      conn.clear_settings!
-      [:@@db_spec_cache, :@@host_spec_cache, :@@default_spec].each do |class_variable|
-        conn.remove_class_variable(class_variable)
-      end
-      conn.set_current_db
-      SiteSetting.provider = @original_provider
-    end
-
-    it "keeps the variable specific to the current site" do
-      class_with_set = Class.new do
-        include MultisiteClassVar
-        multisite_class_var(:class_set) { Set.new }
-      end
-
-      conn.with_connection('default') do
-        expect(class_with_set.class_set).to be_blank
-        class_with_set.class_set << 'item0'
-      end
-
-      conn.with_connection('second') do
-        expect(class_with_set.class_set).to be_blank
-        class_with_set.class_set << 'item1'
-      end
-
-      conn.with_connection('default') do
-        expect(class_with_set.class_set).to contain_exactly('item0')
-      end
-
-      conn.with_connection('second') do
-        expect(class_with_set.class_set).to contain_exactly('item1')
-      end
-
-    end
-  end
-
-end