[Misc] Remove memoist gem dependency

The author has passed away and  some functionality is broken with recent
ruby versions already. We only use a subset of it, so it's easy to replace.

Some places:
* Didn't even use it
* Used it but the method was already cached through memcached
* Just don't need it

Some places I question if it is needed but I'll just leave them there
since I don't want to benchmark

Gemfile

@@ -13,7 +13,6 @@ gem 'draper'
 gem 'streamio-ffmpeg'
 gem 'responders'
 gem 'dtext_rb', :git => "https://github.com/e621ng/dtext_rb.git", branch: "master", :require => "dtext"
-gem 'memoist'
 gem 'bootsnap'
 gem 'addressable'
 gem 'httparty'

Gemfile.lock

@@ -175,7 +175,6 @@ GEM
     mailgun-ruby (1.2.10)
       rest-client (>= 2.0.2)
     marcel (1.0.2)
-    memoist (0.16.2)
     method_source (1.0.0)
     mime-types (3.5.0)
       mime-types-data (~> 3.2015)
@@ -385,7 +384,6 @@ DEPENDENCIES
   listen
   mailgun-ruby
   marcel
-  memoist
   mocha
   newrelic_rpm
   opensearch-ruby

app/logical/sources/strategies/base.rb

@@ -16,8 +16,6 @@ module Sources
     class Base
       attr_reader :url, :urls, :parsed_url
 
-      extend Memoist
-
       # * <tt>url</tt> - Should point to a resource suitable for 
       #   downloading. This may sometimes point to the binary file. 
       #   It may also point to the artist's profile page, in cases
@@ -96,12 +94,6 @@ module Sources
         return Danbooru.config.http_headers
       end
 
-      # Returns the size of the image resource without actually downloading the file.
-      def size
-        Downloads::File.new(image_url).size
-      end
-      memoize :size
-
       def file_url
         image_url
       end

app/logical/upload_service/replacer.rb

@@ -1,7 +1,5 @@
 class UploadService
   class Replacer
-    extend Memoist
-
     attr_reader :post, :replacement
 
     def initialize(post:, replacement:)

app/models/artist.rb

@@ -1,5 +1,4 @@
 class Artist < ApplicationRecord
-  extend Memoist
   class RevertError < Exception ; end
 
   attr_accessor :url_string_changed
@@ -191,10 +190,6 @@ class Artist < ApplicationRecord
       end
     end
 
-    included do
-      memoize :domains
-    end
-
     def sorted_urls
       urls.sort {|a, b| b.priority <=> a.priority}
     end
@@ -337,8 +332,6 @@ class Artist < ApplicationRecord
     end
 
     def reload(options = nil)
-      flush_cache
-
       if instance_variable_defined?(:@notes)
         remove_instance_variable(:@notes)
       end

app/models/dmail_filter.rb

@@ -1,6 +1,4 @@
 class DmailFilter < ApplicationRecord
-  extend Memoist
-
   belongs_to :user
   validates :user, presence: true
   before_validation :initialize_user
@@ -21,9 +19,9 @@ class DmailFilter < ApplicationRecord
   end
 
   def regexp
-    union = words.split(/[[:space:]]+/).map { |word| Regexp.escape(word) }.join("|")
-    /\b#{union}\b/i
+    @regexp ||= begin
+      union = words.split(/[[:space:]]+/).map { |word| Regexp.escape(word) }.join("|")
+      /\b#{union}\b/i
+    end
   end
-
-  memoize :regexp
 end

app/models/post_version.rb

@@ -1,7 +1,5 @@
 class PostVersion < ApplicationRecord
   class UndoError < StandardError; end
-  extend Memoist
-
   belongs_to :post
   belongs_to_updater
   user_status_counter :post_update_count, foreign_key: :updater_id
@@ -167,7 +165,7 @@ class PostVersion < ApplicationRecord
   end
 
   def tag_array
-    (tags || "").split
+    @tag_array ||= tags.split
   end
 
   def locked_tag_array
@@ -178,23 +176,20 @@ class PostVersion < ApplicationRecord
     PostVersionPresenter.new(self)
   end
 
-  def reload
-    flush_cache
-    super
-  end
-
   def previous
     # HACK: If this if the first version we can avoid a lookup because we know there are no previous versions.
     if version <= 1
       return nil
     end
 
+    return @previous if defined?(@previous)
+
     # HACK: if all the post versions for this post have already been preloaded,
     # we can use that to avoid a SQL query.
     if association(:post).loaded? && post && post.association(:versions).loaded?
-      post.versions.sort_by(&:version).reverse.find {|v| v.version < version}
+      @previous = post.versions.sort_by(&:version).reverse.find { |v| v.version < version }
     else
-      PostVersion.where("post_id = ? and version < ?", post_id, version).order("version desc").first
+      @previous = PostVersion.where("post_id = ? and version < ?", post_id, version).order("version desc").first
     end
   end
 
@@ -251,12 +246,14 @@ class PostVersion < ApplicationRecord
   end
 
   def changes
+    return @changes if defined?(@changes)
+
     delta = {
-        :added_tags => added_tags,
-        :removed_tags => removed_tags,
-        :obsolete_removed_tags => [],
-        :obsolete_added_tags => [],
-        :unchanged_tags => []
+      added_tags: added_tags,
+      removed_tags: removed_tags,
+      obsolete_removed_tags: [],
+      obsolete_added_tags: [],
+      unchanged_tags: [],
     }
 
     latest_tags = post.tag_array
@@ -301,7 +298,7 @@ class PostVersion < ApplicationRecord
       delta[:unchanged_tags] = []
     end
 
-    delta
+    @changes = delta
   end
 
   def undo
@@ -371,6 +368,4 @@ class PostVersion < ApplicationRecord
       changes[:unchanged_tags].join(" ")
     end
   end
-
-  memoize :previous, :tag_array, :changes
 end

app/models/tag_implication.rb

@@ -1,6 +1,4 @@
 class TagImplication < TagRelationship
-  extend Memoist
-
   has_many :tag_rel_undos, as: :tag_rel
 
   array_attribute :descendant_names
@@ -17,7 +15,6 @@ class TagImplication < TagRelationship
 
   module DescendantMethods
     extend ActiveSupport::Concern
-    extend Memoist
 
     module ClassMethods
       # assumes names are normalized
@@ -40,16 +37,18 @@ class TagImplication < TagRelationship
     end
 
     def descendants
-      [].tap do |all|
+      @descendants ||= begin
+        result = []
         children = [consequent_name]
 
         until children.empty?
-          all.concat(children)
+          result.concat(children)
           children = TagImplication.active.where(antecedent_name: children).pluck(:consequent_name)
         end
-      end.sort.uniq
+
+        result.sort.uniq
+      end
     end
-    memoize :descendants
 
     def invalidate_cached_descendants
       descendant_names.each do |tag_name|
@@ -76,12 +75,9 @@ class TagImplication < TagRelationship
   end
 
   module ParentMethods
-    extend Memoist
-
     def parents
-      self.class.duplicate_relevant.where("consequent_name = ?", antecedent_name)
+      @parents ||= self.class.duplicate_relevant.where(consequent_name: antecedent_name)
     end
-    memoize :parents
   end
 
   module ValidationMethods
@@ -118,8 +114,6 @@ class TagImplication < TagRelationship
   end
 
   module ApprovalMethods
-    extend Memoist
-
     def process!(update_topic: true)
       unless valid?
         raise errors.full_messages.join("; ")
@@ -208,7 +202,6 @@ class TagImplication < TagRelationship
         skip_update: !TagRelationship::SUPPORT_HARD_CODED
       )
     end
-    memoize :forum_updater
 
     def process_undo!(update_topic: true)
       unless valid?
@@ -261,4 +254,9 @@ class TagImplication < TagRelationship
     flush_cache
     super
   end
+
+  def flush_cache
+    @dedescendants = nil
+    @parents = nil
+  end
 end

app/models/user.rb

@@ -430,8 +430,6 @@ class User < ApplicationRecord
   end
 
   module LimitMethods
-    extend Memoist
-
     def younger_than(duration)
       return false if Danbooru.config.disable_age_checks?
       created_at > duration.ago
@@ -554,41 +552,39 @@ class User < ApplicationRecord
     end
 
     def hourly_upload_limit
-      post_count = posts.where("created_at >= ?", 1.hour.ago).count
-      replacement_count = can_approve_posts? ? 0 : post_replacements.where("created_at >= ? and status != ?", 1.hour.ago, "original").count
-      Danbooru.config.hourly_upload_limit - post_count - replacement_count
+      @hourly_upload_limit ||= begin
+        post_count = posts.where("created_at >= ?", 1.hour.ago).count
+        replacement_count = can_approve_posts? ? 0 : post_replacements.where("created_at >= ? and status != ?", 1.hour.ago, "original").count
+        Danbooru.config.hourly_upload_limit - post_count - replacement_count
+      end
     end
-    memoize :hourly_upload_limit
 
     def upload_limit
       pieces = upload_limit_pieces
-
       base_upload_limit + (pieces[:approved] / 10) - (pieces[:deleted] / 4) - pieces[:pending]
     end
-    memoize :upload_limit
 
     def upload_limit_pieces
-      deleted_count = Post.deleted.for_user(id).count
-      rejected_replacement_count = post_replacement_rejected_count
-      replaced_penalize_count = own_post_replaced_penalize_count
-      unapproved_count = Post.pending_or_flagged.for_user(id).count
-      unapproved_replacements_count = post_replacements.pending.count
-      approved_count = Post.for_user(id).where('is_flagged = false AND is_deleted = false AND is_pending = false').count
+      @upload_limit_pieces ||= begin
+        deleted_count = Post.deleted.for_user(id).count
+        rejected_replacement_count = post_replacement_rejected_count
+        replaced_penalize_count = own_post_replaced_penalize_count
+        unapproved_count = Post.pending_or_flagged.for_user(id).count
+        unapproved_replacements_count = post_replacements.pending.count
+        approved_count = Post.for_user(id).where(is_flagged: false, is_deleted: false, is_pending: false).count
 
-      {
-        deleted: deleted_count + replaced_penalize_count + rejected_replacement_count,
-        deleted_ignore: own_post_replaced_count - replaced_penalize_count,
-        approved: approved_count,
-        pending: unapproved_count + unapproved_replacements_count
-      }
+        {
+          deleted: deleted_count + replaced_penalize_count + rejected_replacement_count,
+          deleted_ignore: own_post_replaced_count - replaced_penalize_count,
+          approved: approved_count,
+          pending: unapproved_count + unapproved_replacements_count,
+        }
+      end
     end
-    memoize :upload_limit_pieces
 
     def post_upload_throttle
-      return hourly_upload_limit if is_privileged?
-      [hourly_upload_limit, post_edit_limit].min
+      @post_upload_throttle ||= is_privileged? ? hourly_upload_limit : [hourly_upload_limit, post_edit_limit].min
     end
-    memoize :post_upload_throttle
 
     def tag_query_limit
       Danbooru.config.tag_query_limit

app/models/wiki_page_version.rb

@@ -4,9 +4,7 @@ class WikiPageVersion < ApplicationRecord
   belongs_to_updater
   user_status_counter :wiki_edit_count, foreign_key: :updater_id
   belongs_to :artist, optional: true
-  delegate :visible?, :to => :wiki_page
-
-  extend Memoist
+  delegate :visible?, to: :wiki_page
 
   module SearchMethods
     def for_user(user_id)
@@ -42,9 +40,9 @@ class WikiPageVersion < ApplicationRecord
   end
 
   def previous
-    WikiPageVersion.where("wiki_page_id = ? and id < ?", wiki_page_id, id).order("id desc").first
+    return @previous if defined?(@previous)
+    @previous = WikiPageVersion.where("wiki_page_id = ? and id < ?", wiki_page_id, id).order("id desc").first
   end
-  memoize :previous
 
   def category_id
     Tag.category_for(title)