models: drop unnecessary presence validations.

In rails 5, belongs_to associations automatically validate that the
associated item is present, meaning that we don't need to validate these
things manually any more.

app/models/ban.rb

@@ -7,7 +7,7 @@ class Ban < ApplicationRecord
   belongs_to :user
   belongs_to :banner, :class_name => "User"
   validate :user_is_inferior
-  validates_presence_of :user_id, :reason, :duration
+  validates_presence_of :reason, :duration
   before_validation :initialize_banner_id, :on => :create
 
   scope :unexpired, -> { where("bans.expires_at > ?", Time.now) }

app/models/bulk_update_request.rb

@@ -6,7 +6,6 @@ class BulkUpdateRequest < ApplicationRecord
   belongs_to :forum_post, optional: true
   belongs_to :approver, optional: true, class_name: "User"
 
-  validates_presence_of :user
   validates_presence_of :script
   validates_presence_of :title, if: ->(rec) {rec.forum_topic_id.blank?}
   validates_inclusion_of :status, :in => %w(pending approved rejected)

app/models/comment.rb

@@ -136,10 +136,6 @@ class Comment < ApplicationRecord
   extend SearchMethods
   include VoteMethods
 
-  def validate_post_exists
-    errors.add(:post, "must exist") unless Post.exists?(post_id)
-  end
-
   def validate_creator_is_not_limited
     if creator.is_comment_limited? && !do_not_bump_post?
       errors.add(:base, "You can only post #{Danbooru.config.member_comment_limit} comments per hour")

app/models/comment_vote.rb

@@ -4,7 +4,7 @@ class CommentVote < ApplicationRecord
   belongs_to :comment
   belongs_to :user
   before_validation :initialize_user, :on => :create
-  validates_presence_of :user_id, :comment_id, :score
+  validates_presence_of :score
   validates_uniqueness_of :user_id, :scope => :comment_id, :message => "have already voted for this comment"
   validate :validate_user_can_vote
   validate :validate_comment_can_be_down_voted

app/models/dmail_filter.rb

@@ -2,7 +2,6 @@ class DmailFilter < ApplicationRecord
   extend Memoist
 
   belongs_to :user
-  validates_presence_of :user
   before_validation :initialize_user
 
   def initialize_user

app/models/forum_post.rb

@@ -13,9 +13,8 @@ class ForumPost < ApplicationRecord
   after_create :update_topic_updated_at_on_create
   after_update :update_topic_updated_at_on_update_for_original_posts
   after_destroy :update_topic_updated_at_on_destroy
-  validates_presence_of :body, :creator_id
+  validates_presence_of :body
   validate :validate_topic_is_unlocked
-  validate :topic_id_not_invalid
   validate :topic_is_not_restricted, :on => :create
   before_destroy :validate_topic_is_unlocked
   after_save :delete_topic_if_original_post
@@ -144,13 +143,6 @@ class ForumPost < ApplicationRecord
     end
   end
 
-  def topic_id_not_invalid
-    if topic_id && !topic
-      errors[:base] << "Topic ID is invalid"
-      return false
-    end
-  end
-
   def topic_is_not_restricted
     if topic && !topic.visible?(creator)
       errors[:topic] << "is restricted"

app/models/forum_topic.rb

@@ -17,7 +17,7 @@ class ForumTopic < ApplicationRecord
   has_one :original_post, -> {order("forum_posts.id asc")}, class_name: "ForumPost", foreign_key: "topic_id", inverse_of: :topic
   has_many :subscriptions, :class_name => "ForumSubscription"
   before_validation :initialize_is_deleted, :on => :create
-  validates_presence_of :title, :creator_id
+  validates_presence_of :title
   validates_associated :original_post
   validates_inclusion_of :category_id, :in => CATEGORIES.keys
   validates_inclusion_of :min_level, :in => MIN_LEVELS.values

app/models/ip_ban.rb

@@ -1,7 +1,7 @@
 class IpBan < ApplicationRecord
   IP_ADDR_REGEX = /\A(?:[0-9]{1,3}\.){3}[0-9]{1,3}\Z/
   belongs_to_creator
-  validates_presence_of :reason, :creator, :ip_addr
+  validates_presence_of :reason, :ip_addr
   validates_format_of :ip_addr, :with => IP_ADDR_REGEX
   validates_uniqueness_of :ip_addr, :if => ->(rec) {rec.ip_addr =~ IP_ADDR_REGEX}
   after_create do |rec|

app/models/janitor_trial.rb

@@ -2,7 +2,6 @@ class JanitorTrial < ApplicationRecord
   belongs_to :user
   after_create :send_dmail
   after_create :promote_user
-  validates_presence_of :user
   belongs_to_creator
   validates_inclusion_of :status, :in => %w(active inactive)
   before_validation :initialize_status

app/models/mod_action.rb

@@ -1,7 +1,6 @@
 class ModAction < ApplicationRecord
   belongs_to :creator, :class_name => "User"
   before_validation :initialize_creator, :on => :create
-  validates_presence_of :creator_id
 
   #####DIVISIONS#####
   #Groups:     0-999

app/models/note.rb

@@ -5,8 +5,7 @@ class Note < ApplicationRecord
   belongs_to :post
   belongs_to_creator
   has_many :versions, -> {order("note_versions.id ASC")}, :class_name => "NoteVersion", :dependent => :destroy
-  validates_presence_of :creator_id, :x, :y, :width, :height, :body
-  validate :post_must_exist
+  validates_presence_of :x, :y, :width, :height, :body
   validate :note_within_image
   after_save :update_post
   after_save :create_version
@@ -68,13 +67,6 @@ class Note < ApplicationRecord
   extend SearchMethods
   include ApiMethods
 
-  def post_must_exist
-    if !Post.exists?(post_id)
-      errors.add :post, "must exist"
-      return false
-    end
-  end
-
   def post_must_not_be_note_locked
     if is_locked?
       errors.add :post, "is note locked"

app/models/post_appeal.rb

@@ -3,7 +3,7 @@ class PostAppeal < ApplicationRecord
 
   belongs_to :creator, :class_name => "User"
   belongs_to :post
-  validates_presence_of :post, :reason, :creator_id, :creator_ip_addr
+  validates_presence_of :reason, :creator_ip_addr
   validate :validate_post_is_inactive
   validate :validate_creator_is_not_limited
   before_validation :initialize_creator, :on => :create

app/models/post_vote.rb

@@ -6,7 +6,7 @@ class PostVote < ApplicationRecord
   attr_accessor :vote
 
   after_initialize :initialize_attributes, if: :new_record?
-  validates_presence_of :post_id, :user_id, :score
+  validates_presence_of :score
   validates_inclusion_of :score, :in => [SuperVoter::MAGNITUDE, 1, -1, -SuperVoter::MAGNITUDE]
   after_create :update_post_on_create
   after_destroy :update_post_on_destroy

app/models/tag_relationship.rb

@@ -27,8 +27,7 @@ class TagRelationship < ApplicationRecord
   before_validation :initialize_creator, :on => :create
   before_validation :normalize_names
   validates_format_of :status, :with => /\A(active|deleted|pending|processing|queued|retired|error: .*)\Z/
-  validates_presence_of :creator_id, :antecedent_name, :consequent_name
-  validates :creator, presence: { message: "must exist" }, if: -> { creator_id.present? }
+  validates_presence_of :antecedent_name, :consequent_name
   validates :approver, presence: { message: "must exist" }, if: -> { approver_id.present? }
   validates :forum_topic, presence: { message: "must exist" }, if: -> { forum_topic_id.present? }
   validate :antecedent_and_consequent_are_different

app/models/user_feedback.rb

@@ -3,7 +3,7 @@ class UserFeedback < ApplicationRecord
   belongs_to :user
   belongs_to_creator
   attr_accessor :disable_dmail_notification
-  validates_presence_of :user, :creator, :body, :category
+  validates_presence_of :body, :category
   validates_inclusion_of :category, :in => %w(positive negative neutral)
   validate :creator_is_gold
   validate :user_is_not_creator

app/models/user_name_change_request.rb

@@ -1,6 +1,6 @@
 class UserNameChangeRequest < ApplicationRecord
   after_initialize :initialize_attributes, if: :new_record?
-  validates_presence_of :user_id, :original_name, :desired_name
+  validates_presence_of :original_name, :desired_name
   validates_inclusion_of :status, :in => %w(pending approved rejected)
   belongs_to :user
   belongs_to :approver, :class_name => "User", optional: true