Added Cop to blacklist the use of `dependent:`

This is allowed for existing instances so we don't end up 76 offenses
right away, but for new code one should _only_ use this if they _have_
to remove non database data. Even then it's usually better to do this in
a service class as this gives you more control over how to remove the
data (e.g. in bulk).

app/models/appearance.rb

@@ -10,5 +10,5 @@ class Appearance < ActiveRecord::Base
 
   mount_uploader :logo,         AttachmentUploader
   mount_uploader :header_logo,  AttachmentUploader
-  has_many :uploads, as: :model, dependent: :destroy
+  has_many :uploads, as: :model, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 end

app/models/board.rb

 class Board < ActiveRecord::Base
   belongs_to :project
 
-  has_many :lists, -> { order(:list_type, :position) }, dependent: :delete_all
+  has_many :lists, -> { order(:list_type, :position) }, dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
 
   validates :project, presence: true
 

app/models/ci/pipeline.rb

@@ -14,7 +14,7 @@ module Ci
     has_many :stages
     has_many :statuses, class_name: 'CommitStatus', foreign_key: :commit_id
     has_many :builds, foreign_key: :commit_id
-    has_many :trigger_requests, dependent: :destroy, foreign_key: :commit_id
+    has_many :trigger_requests, dependent: :destroy, foreign_key: :commit_id # rubocop:disable Cop/ActiveRecordDependent
 
     # Merge requests for which the current pipeline is running against
     # the merge request's latest commit.

app/models/ci/runner.rb

@@ -8,7 +8,7 @@ module Ci
     FORM_EDITABLE = %i[description tag_list active run_untagged locked].freeze
 
     has_many :builds
-    has_many :runner_projects, dependent: :destroy
+    has_many :runner_projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
     has_many :projects, through: :runner_projects
 
     has_one :last_build, ->() { order('id DESC') }, class_name: 'Ci::Build'

app/models/concerns/awardable.rb

@@ -2,7 +2,7 @@ module Awardable
   extend ActiveSupport::Concern
 
   included do
-    has_many :award_emoji, -> { includes(:user).order(:id) }, as: :awardable, dependent: :destroy
+    has_many :award_emoji, -> { includes(:user).order(:id) }, as: :awardable, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
     if self < Participable
       # By default we always load award_emoji user association

app/models/concerns/issuable.rb

@@ -30,7 +30,7 @@ module Issuable
     belongs_to :updated_by, class_name: "User"
     belongs_to :last_edited_by, class_name: 'User'
     belongs_to :milestone
-    has_many :notes, as: :noteable, inverse_of: :noteable, dependent: :destroy do
+    has_many :notes, as: :noteable, inverse_of: :noteable, dependent: :destroy do # rubocop:disable Cop/ActiveRecordDependent
       def authors_loaded?
         # We check first if we're loaded to not load unnecessarily.
         loaded? && to_a.all? { |note| note.association(:author).loaded? }
@@ -42,9 +42,9 @@ module Issuable
       end
     end
 
-    has_many :label_links, as: :target, dependent: :destroy
+    has_many :label_links, as: :target, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
     has_many :labels, through: :label_links
-    has_many :todos, as: :target, dependent: :destroy
+    has_many :todos, as: :target, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
     has_one :metrics
 

app/models/concerns/protected_ref.rb

@@ -17,7 +17,7 @@ module ProtectedRef
   class_methods do
     def protected_ref_access_levels(*types)
       types.each do |type|
-        has_many :"#{type}_access_levels", dependent: :destroy
+        has_many :"#{type}_access_levels", dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
         validates :"#{type}_access_levels", length: { is: 1, message: "are restricted to a single instance per #{self.model_name.human}." }
 

app/models/concerns/routable.rb

@@ -4,8 +4,8 @@ module Routable
   extend ActiveSupport::Concern
 
   included do
-    has_one :route, as: :source, autosave: true, dependent: :destroy
-    has_many :redirect_routes, as: :source, autosave: true, dependent: :destroy
+    has_one :route, as: :source, autosave: true, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+    has_many :redirect_routes, as: :source, autosave: true, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
     validates_associated :route
     validates :route, presence: true

app/models/concerns/spammable.rb

@@ -8,7 +8,7 @@ module Spammable
   end
 
   included do
-    has_one :user_agent_detail, as: :subject, dependent: :destroy
+    has_one :user_agent_detail, as: :subject, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
     attr_accessor :spam
     attr_accessor :spam_log

app/models/concerns/subscribable.rb

@@ -9,7 +9,7 @@ module Subscribable
   extend ActiveSupport::Concern
 
   included do
-    has_many :subscriptions, dependent: :destroy, as: :subscribable
+    has_many :subscriptions, dependent: :destroy, as: :subscribable # rubocop:disable Cop/ActiveRecordDependent
   end
 
   def subscribed?(user, project = nil)

app/models/concerns/time_trackable.rb

@@ -18,7 +18,7 @@ module TimeTrackable
     validates :time_estimate, numericality: { message: 'has an invalid format' }, allow_nil: false
     validate  :check_negative_time_spent
 
-    has_many :timelogs, dependent: :destroy
+    has_many :timelogs, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   end
 
   def spend_time(options)

app/models/deploy_key.rb

 class DeployKey < Key
-  has_many :deploy_keys_projects, dependent: :destroy
+  has_many :deploy_keys_projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :projects, through: :deploy_keys_projects
 
   scope :in_projects, ->(projects) { joins(:deploy_keys_projects).where('deploy_keys_projects.project_id in (?)', projects) }

app/models/environment.rb

@@ -6,7 +6,7 @@ class Environment < ActiveRecord::Base
 
   belongs_to :project, required: true, validate: true
 
-  has_many :deployments, dependent: :destroy
+  has_many :deployments, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_one :last_deployment, -> { order('deployments.id DESC') }, class_name: 'Deployment'
 
   before_validation :nullify_external_url

app/models/group.rb

@@ -8,7 +8,7 @@ class Group < Namespace
   include Referable
   include SelectForProjectAuthorization
 
-  has_many :group_members, -> { where(requested_at: nil) }, dependent: :destroy, as: :source
+  has_many :group_members, -> { where(requested_at: nil) }, dependent: :destroy, as: :source # rubocop:disable Cop/ActiveRecordDependent
   alias_method :members, :group_members
   has_many :users, through: :group_members
   has_many :owners,
@@ -16,11 +16,11 @@ class Group < Namespace
     through: :group_members,
     source: :user
 
-  has_many :requesters, -> { where.not(requested_at: nil) }, dependent: :destroy, as: :source, class_name: 'GroupMember'
+  has_many :requesters, -> { where.not(requested_at: nil) }, dependent: :destroy, as: :source, class_name: 'GroupMember' # rubocop:disable Cop/ActiveRecordDependent
 
-  has_many :project_group_links, dependent: :destroy
+  has_many :project_group_links, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :shared_projects, through: :project_group_links, source: :project
-  has_many :notification_settings, dependent: :destroy, as: :source
+  has_many :notification_settings, dependent: :destroy, as: :source # rubocop:disable Cop/ActiveRecordDependent
   has_many :labels, class_name: 'GroupLabel'
 
   validate :avatar_type, if: ->(user) { user.avatar.present? && user.avatar_changed? }
@@ -31,7 +31,7 @@ class Group < Namespace
   validates :two_factor_grace_period, presence: true, numericality: { greater_than_or_equal_to: 0 }
 
   mount_uploader :avatar, AvatarUploader
-  has_many :uploads, as: :model, dependent: :destroy
+  has_many :uploads, as: :model, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   after_create :post_create_hook
   after_destroy :post_destroy_hook

app/models/hooks/web_hook.rb

@@ -12,7 +12,7 @@ class WebHook < ActiveRecord::Base
   default_value_for :repository_update_events, false
   default_value_for :enable_ssl_verification, true
 
-  has_many :web_hook_logs, dependent: :destroy
+  has_many :web_hook_logs, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   scope :push_hooks, -> { where(push_events: true) }
   scope :tag_push_hooks, -> { where(tag_push_events: true) }

app/models/issue.rb

@@ -23,9 +23,14 @@ class Issue < ActiveRecord::Base
   belongs_to :project
   belongs_to :moved_to, class_name: 'Issue'
 
-  has_many :events, as: :target, dependent: :destroy
+  has_many :events, as: :target, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
-  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues'
+  has_many :merge_requests_closing_issues,
+    class_name: 'MergeRequestsClosingIssues',
+    dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
+
+  has_many :issue_assignees
+  has_many :assignees, class_name: "User", through: :issue_assignees
 
   has_many :issue_assignees
   has_many :assignees, class_name: "User", through: :issue_assignees

app/models/label.rb

@@ -15,9 +15,9 @@ class Label < ActiveRecord::Base
 
   default_value_for :color, DEFAULT_COLOR
 
-  has_many :lists, dependent: :destroy
+  has_many :lists, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :priorities, class_name: 'LabelPriority'
-  has_many :label_links, dependent: :destroy
+  has_many :label_links, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :issues, through: :label_links, source: :target, source_type: 'Issue'
   has_many :merge_requests, through: :label_links, source: :target, source_type: 'MergeRequest'
 

app/models/lfs_object.rb

 class LfsObject < ActiveRecord::Base
-  has_many :lfs_objects_projects, dependent: :destroy
+  has_many :lfs_objects_projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :projects, through: :lfs_objects_projects
 
   validates :oid, presence: true, uniqueness: true

app/models/merge_request.rb

@@ -18,9 +18,11 @@ class MergeRequest < ActiveRecord::Base
 
   belongs_to :head_pipeline, foreign_key: "head_pipeline_id", class_name: "Ci::Pipeline"
 
-  has_many :events, as: :target, dependent: :destroy
+  has_many :events, as: :target, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
-  has_many :merge_requests_closing_issues, class_name: 'MergeRequestsClosingIssues'
+  has_many :merge_requests_closing_issues,
+    class_name: 'MergeRequestsClosingIssues',
+    dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
 
   belongs_to :assignee, class_name: "User"
 

app/models/milestone.rb

@@ -21,7 +21,7 @@ class Milestone < ActiveRecord::Base
   has_many :issues
   has_many :labels, -> { distinct.reorder('labels.title') },  through: :issues
   has_many :merge_requests
-  has_many :events, as: :target, dependent: :destroy
+  has_many :events, as: :target, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   scope :active, -> { with_state(:active) }
   scope :closed, -> { with_state(:closed) }

app/models/namespace.rb

@@ -15,13 +15,13 @@ class Namespace < ActiveRecord::Base
 
   cache_markdown_field :description, pipeline: :description
 
-  has_many :projects, dependent: :destroy
+  has_many :projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :project_statistics
   belongs_to :owner, class_name: "User"
 
   belongs_to :parent, class_name: "Namespace"
   has_many :children, class_name: "Namespace", foreign_key: :parent_id
-  has_one :chat_team, dependent: :destroy
+  has_one :chat_team, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   validates :owner, presence: true, unless: ->(n) { n.type == "Group" }
   validates :name,

app/models/note.rb

@@ -46,8 +46,8 @@ class Note < ActiveRecord::Base
   belongs_to :updated_by, class_name: "User"
   belongs_to :last_edited_by, class_name: 'User'
 
-  has_many :todos, dependent: :destroy
-  has_many :events, as: :target, dependent: :destroy
+  has_many :todos, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :events, as: :target, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_one :system_note_metadata
 
   delegate :gfm_reference, :local_reference, to: :noteable

app/models/project.rb

@@ -138,26 +138,26 @@ class Project < ActiveRecord::Base
   has_many :project_authorizations
   has_many :authorized_users, through: :project_authorizations, source: :user, class_name: 'User'
   has_many :project_members, -> { where(requested_at: nil) },
-    as: :source, dependent: :delete_all
+    as: :source, dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
 
   alias_method :members, :project_members
   has_many :users, through: :project_members
 
   has_many :requesters, -> { where.not(requested_at: nil) },
-    as: :source, class_name: 'ProjectMember', dependent: :delete_all
+    as: :source, class_name: 'ProjectMember', dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
 
   has_many :deploy_keys_projects
   has_many :deploy_keys, through: :deploy_keys_projects
   has_many :users_star_projects
   has_many :starrers, through: :users_star_projects, source: :user
   has_many :releases
-  has_many :lfs_objects_projects, dependent: :destroy
+  has_many :lfs_objects_projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :lfs_objects, through: :lfs_objects_projects
   has_many :project_group_links
   has_many :invited_groups, through: :project_group_links, source: :group
   has_many :pages_domains
   has_many :todos
-  has_many :notification_settings, as: :source, dependent: :delete_all
+  has_many :notification_settings, as: :source, dependent: :delete_all # rubocop:disable Cop/ActiveRecordDependent
 
   has_one :import_data, class_name: 'ProjectImportData'
   has_one :project_feature
@@ -166,7 +166,7 @@ class Project < ActiveRecord::Base
   # Container repositories need to remove data from the container registry,
   # which is not managed by the DB. Hence we're still using dependent: :destroy
   # here.
-  has_many :container_repositories, dependent: :destroy
+  has_many :container_repositories, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   has_many :commit_statuses
   has_many :pipelines, class_name: 'Ci::Pipeline'
@@ -175,7 +175,7 @@ class Project < ActiveRecord::Base
   # build traces. Currently there's no efficient way of removing this data in
   # bulk that doesn't involve loading the rows into memory. As a result we're
   # still using `dependent: :destroy` here.
-  has_many :builds, class_name: 'Ci::Build', dependent: :destroy
+  has_many :builds, class_name: 'Ci::Build', dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :runner_projects, class_name: 'Ci::RunnerProject'
   has_many :runners, through: :runner_projects, source: :runner, class_name: 'Ci::Runner'
   has_many :variables, class_name: 'Ci::Variable'
@@ -237,7 +237,7 @@ class Project < ActiveRecord::Base
   before_save :ensure_runners_token
 
   mount_uploader :avatar, AvatarUploader
-  has_many :uploads, as: :model, dependent: :destroy
+  has_many :uploads, as: :model, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   # Scopes
   scope :pending_delete, -> { where(pending_delete: true) }

app/models/project_services/slash_commands_service.rb

@@ -5,7 +5,7 @@ class SlashCommandsService < Service
 
   prop_accessor :token
 
-  has_many :chat_names, foreign_key: :service_id, dependent: :destroy
+  has_many :chat_names, foreign_key: :service_id, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   def valid_token?(token)
     self.respond_to?(:token) &&

app/models/snippet.rb

@@ -30,7 +30,7 @@ class Snippet < ActiveRecord::Base
   belongs_to :author, class_name: 'User'
   belongs_to :project
 
-  has_many :notes, as: :noteable, dependent: :destroy
+  has_many :notes, as: :noteable, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   delegate :name, :email, to: :author, prefix: true, allow_nil: true
 

app/models/user.rb

@@ -67,24 +67,24 @@ class User < ActiveRecord::Base
   #
 
   # Namespace for personal projects
-  has_one :namespace, -> { where type: nil }, dependent: :destroy, foreign_key: :owner_id, autosave: true
+  has_one :namespace, -> { where type: nil }, dependent: :destroy, foreign_key: :owner_id, autosave: true # rubocop:disable Cop/ActiveRecordDependent
 
   # Profile
   has_many :keys, -> do
     type = Key.arel_table[:type]
     where(type.not_eq('DeployKey').or(type.eq(nil)))
-  end, dependent: :destroy
-  has_many :deploy_keys, -> { where(type: 'DeployKey') }, dependent: :destroy
+  end, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :deploy_keys, -> { where(type: 'DeployKey') }, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
-  has_many :emails, dependent: :destroy
-  has_many :personal_access_tokens, dependent: :destroy
-  has_many :identities, dependent: :destroy, autosave: true
-  has_many :u2f_registrations, dependent: :destroy
-  has_many :chat_names, dependent: :destroy
+  has_many :emails, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :personal_access_tokens, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :identities, dependent: :destroy, autosave: true # rubocop:disable Cop/ActiveRecordDependent
+  has_many :u2f_registrations, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :chat_names, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   # Groups
-  has_many :members, dependent: :destroy
-  has_many :group_members, -> { where(requested_at: nil) }, dependent: :destroy, source: 'GroupMember'
+  has_many :members, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :group_members, -> { where(requested_at: nil) }, dependent: :destroy, source: 'GroupMember' # rubocop:disable Cop/ActiveRecordDependent
   has_many :groups, through: :group_members
   has_many :owned_groups, -> { where members: { access_level: Gitlab::Access::OWNER } }, through: :group_members, source: :group
   has_many :masters_groups, -> { where members: { access_level: Gitlab::Access::MASTER } }, through: :group_members, source: :group
@@ -92,35 +92,35 @@ class User < ActiveRecord::Base
   # Projects
   has_many :groups_projects,          through: :groups, source: :projects
   has_many :personal_projects,        through: :namespace, source: :projects
-  has_many :project_members, -> { where(requested_at: nil) }, dependent: :destroy
+  has_many :project_members, -> { where(requested_at: nil) }, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :projects,                 through: :project_members
   has_many :created_projects,         foreign_key: :creator_id, class_name: 'Project'
-  has_many :users_star_projects, dependent: :destroy
+  has_many :users_star_projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :starred_projects, through: :users_star_projects, source: :project
   has_many :project_authorizations
   has_many :authorized_projects, through: :project_authorizations, source: :project
 
-  has_many :snippets,                 dependent: :destroy, foreign_key: :author_id
-  has_many :notes,                    dependent: :destroy, foreign_key: :author_id
-  has_many :issues,                   dependent: :destroy, foreign_key: :author_id
-  has_many :merge_requests,           dependent: :destroy, foreign_key: :author_id
-  has_many :events,                   dependent: :destroy, foreign_key: :author_id
-  has_many :subscriptions,            dependent: :destroy
+  has_many :snippets,                 dependent: :destroy, foreign_key: :author_id # rubocop:disable Cop/ActiveRecordDependent
+  has_many :notes,                    dependent: :destroy, foreign_key: :author_id # rubocop:disable Cop/ActiveRecordDependent
+  has_many :issues,                   dependent: :destroy, foreign_key: :author_id # rubocop:disable Cop/ActiveRecordDependent
+  has_many :merge_requests,           dependent: :destroy, foreign_key: :author_id # rubocop:disable Cop/ActiveRecordDependent
+  has_many :events,                   dependent: :destroy, foreign_key: :author_id # rubocop:disable Cop/ActiveRecordDependent
+  has_many :subscriptions,            dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
   has_many :recent_events, -> { order "id DESC" }, foreign_key: :author_id,   class_name: "Event"
-  has_many :oauth_applications, class_name: 'Doorkeeper::Application', as: :owner, dependent: :destroy
-  has_one  :abuse_report,             dependent: :destroy, foreign_key: :user_id
-  has_many :reported_abuse_reports,   dependent: :destroy, foreign_key: :reporter_id, class_name: "AbuseReport"
-  has_many :spam_logs,                dependent: :destroy
-  has_many :builds,                   dependent: :nullify, class_name: 'Ci::Build'
-  has_many :pipelines,                dependent: :nullify, class_name: 'Ci::Pipeline'
-  has_many :todos,                    dependent: :destroy
-  has_many :notification_settings,    dependent: :destroy
-  has_many :award_emoji,              dependent: :destroy
-  has_many :triggers,                 dependent: :destroy, class_name: 'Ci::Trigger', foreign_key: :owner_id
+  has_many :oauth_applications, class_name: 'Doorkeeper::Application', as: :owner, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_one  :abuse_report,             dependent: :destroy, foreign_key: :user_id # rubocop:disable Cop/ActiveRecordDependent
+  has_many :reported_abuse_reports,   dependent: :destroy, foreign_key: :reporter_id, class_name: "AbuseReport" # rubocop:disable Cop/ActiveRecordDependent
+  has_many :spam_logs,                dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :builds,                   dependent: :nullify, class_name: 'Ci::Build' # rubocop:disable Cop/ActiveRecordDependent
+  has_many :pipelines,                dependent: :nullify, class_name: 'Ci::Pipeline' # rubocop:disable Cop/ActiveRecordDependent
+  has_many :todos,                    dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :notification_settings,    dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :award_emoji,              dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :triggers,                 dependent: :destroy, class_name: 'Ci::Trigger', foreign_key: :owner_id # rubocop:disable Cop/ActiveRecordDependent
 
   has_many :issue_assignees
   has_many :assigned_issues, class_name: "Issue", through: :issue_assignees, source: :issue
-  has_many :assigned_merge_requests,  dependent: :nullify, foreign_key: :assignee_id, class_name: "MergeRequest"
+  has_many :assigned_merge_requests,  dependent: :nullify, foreign_key: :assignee_id, class_name: "MergeRequest" # rubocop:disable Cop/ActiveRecordDependent
 
   #
   # Validations
@@ -211,7 +211,7 @@ class User < ActiveRecord::Base
   end
 
   mount_uploader :avatar, AvatarUploader
-  has_many :uploads, as: :model, dependent: :destroy
+  has_many :uploads, as: :model, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
 
   # Scopes
   scope :admins, -> { where(admin: true) }

rubocop/cop/active_record_dependent.rb

+require_relative '../model_helpers'
+
+module RuboCop
+  module Cop
+    # Cop that prevents the use of `dependent: ...` in ActiveRecord models.
+    class ActiveRecordDependent < RuboCop::Cop::Cop
+      include ModelHelpers
+
+      MSG = 'Do not use `dependent: to remove associated data, ' \
+        'use foreign keys with cascading deletes instead'.freeze
+
+      METHOD_NAMES = [:has_many, :has_one, :belongs_to].freeze
+
+      def on_send(node)
+        return unless in_model?(node)
+        return unless METHOD_NAMES.include?(node.children[1])
+
+        node.children.last.each_node(:pair) do |pair|
+          key_name = pair.children[0].children[0]
+
+          add_offense(pair, :expression) if key_name == :dependent
+        end
+      end
+    end
+  end
+end

rubocop/rubocop.rb

@@ -4,6 +4,7 @@ require_relative 'cop/activerecord_serialize'
 require_relative 'cop/redirect_with_status'
 require_relative 'cop/polymorphic_associations'
 require_relative 'cop/project_path_helper'
+require_relative 'cop/active_record_dependent'
 require_relative 'cop/migration/add_column'
 require_relative 'cop/migration/add_column_with_default_to_large_table'
 require_relative 'cop/migration/add_concurrent_foreign_key'

spec/rubocop/cop/active_record_dependent_spec.rb

+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../rubocop/cop/active_record_dependent'
+
+describe RuboCop::Cop::ActiveRecordDependent do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  context 'inside the app/models directory' do
+    it 'registers an offense when dependent: is used' do
+      allow(cop).to receive(:in_model?).and_return(true)
+
+      inspect_source(cop, 'belongs_to :foo, dependent: :destroy')
+
+      aggregate_failures do
+        expect(cop.offenses.size).to eq(1)
+        expect(cop.offenses.map(&:line)).to eq([1])
+      end
+    end
+  end
+
+  context 'outside the app/models directory' do
+    it 'does nothing' do
+      allow(cop).to receive(:in_model?).and_return(false)
+
+      inspect_source(cop, 'belongs_to :foo, dependent: :destroy')
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+end